CMP Journal 2025-03-04
Statistics
Nature Materials: 1
arXiv: 106
Nature Materials
Non-fullerene electron-transporting materials for high-performance and stable perovskite solar cells
Original Paper | Organic molecules in materials science | 2025-03-03 19:00 EST
Kui Feng, Guoliang Wang, Qing Lian, Sergio Gámez-Valenzuela, Bolin Li, Riqing Ding, Wanli Yang, Keli Wang, Jie Zeng, Yong Zhang, Sang Young Jeong, Baomin Xu, Anita Ho-Baillie, Han Young Woo, Antonio Facchetti, Xugang Guo
The electron-transporting material (ETM) is a key component of perovskite solar cells (PSCs) optimizing electron extraction from perovskite to cathode. Fullerenes, specifically C60 and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), have been used as the benchmark ETMs for inverted PSCs. However, C60 is restricted to thermal evaporation, and PCBM suffers from poor photothermal stability and suboptimal electron transport, limiting their PSC applications. Here a solution-processable non-fullerene ETM, cyano-functionalized bithiophene imide dimer (CNI2)-based polymer (PCNI2-BTI), holds multiple advantages, including excellent photothermal stability, efficient electron transport and improved interaction with the perovskite layer. Consequently, inverted PSCs incorporating PCNI2-BTI deliver an outstanding power conversion efficiency (PCE) of 26.0% (certified 25.4%) and remarkable operational stability, with a T80 approaching 1,300 h under ISOS-L-3. Moreover, we synthesize three additional CNI2-based polymer ETMs, yielding an average PCE of >25% in PSCs. These findings demonstrate unprecedented potential of non-fullerene ETMs enabling high-performance and stable PSCs.
Organic molecules in materials science, Solar cells
arXiv
Comment on arXiv:2501.17230 and arXiv:2502.00103 “Phonon-mediated electron attraction in SrTiO3 via the generalized Frohlich and deformation potential mechanisms” and “Theory of ab initio downfolding with arbitrary range electron-phonon coupling”
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
This comment critically examines the claims made in arXiv papers arXiv:2501.17230 and arXiv:2502.00103, which argue that a multiplicity of polar optical phonons can generate a long-range attractive interaction via a generalized Frohlich coupling. I identify a fundamental flaw in their derivation, showing that their result relies on an unphysical assumption–specifically, neglecting the intermode Coulomb interactions between different polar optical phonons. By restoring these missing interactions I show the screened Coulomb interaction is always repulsive in the static limit.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
FuzzifiED – Julia package for numerics on the fuzzy sphere
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
The Julia package FuzzifiED aims at simplifying the numerical calculations on the fuzzy sphere. It supports exact diagonalisation (ED) and density matrix renormalisation group (DMRG) calculations. FuzzifiED can also apply to generic fermionic and bosonic models. This documentation provides a review of the fuzzy sphere regularisation and an instruction for using FuzzifiED for numerical calculations.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Theory (hep-th)
88 pages. An up-to-date version at this https URL ; the online documentation at this http URL ( this https URL )
Understanding Floquet Resonances in Ultracold Gas Scattering
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Christoph Dauer, Axel Pelster, Sebastian Eggert
Scattering by a short-range potential with time-periodic interaction strength is investigated with a Floquet-scattering theory. Sharp resonances occur, at which the s-wave scattering length can be tuned to large positive and negative values. We show that the shape of these resonances is described by a simple formula, and find that both resonance position and prefactor can be altered by the driving strength. Our approach allows to identify the physical origin of the scattering resonances as Floquet bound states with positive energies, which are dynamically created by the drive. This insight is valuable for a detailed analysis and uncovers a general resource for enhanced or reduced scattering in Floquet systems.
Quantum Gases (cond-mat.quant-gas), Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
7 pages, 2 figures. For the final version and related information see this https URL
Anomalies of Coset Non-Invertible Symmetries
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Po-Shen Hsin, Ryohei Kobayashi, Carolyn Zhang
Anomalies of global symmetries provide important information on the quantum dynamics. We show the dynamical constraints can be organized into three classes: genuine anomalies, fractional topological responses, and integer responses that can be realized in symmetry-protected topological (SPT) phases. Coset symmetry can be present in many physical systems including quantum spin liquids, and the coset symmetry can be a non-invertible symmetry. We introduce twists in coset symmetries, which modify the fusion rules and the generalized Frobenius-Schur indicators. We call such coset symmetries twisted coset symmetries, and they are labeled by the quadruple $(G,K,\omega_{D+1},\alpha_D)$ in $D$ spacetime dimensions where $G$ is a group and $K\subset G$ is a discrete subgroup, $\omega_{D+1}$ is a $(D+1)$-cocycle for group $G$, and $\alpha_{D}$ is a $D$-cochain for group $K$. We present several examples with twisted coset symmetries using lattice models and field theory, including both gapped and gapless systems (such as gapless symmetry-protected topological phases). We investigate the anomalies of general twisted coset symmetry, which presents obstructions to realizing the coset symmetry in (gapped) symmetry-protected topological phases. We show that finite coset symmetry $G/K$ becomes anomalous when $G$ cannot be expressed as the bicrossed product $G=H\Join K$, and such anomalous coset symmetry leads to symmetry-enforced gaplessness in generic spacetime dimensions. We illustrate examples of anomalous coset symmetries with $A_5/\mathbb{Z}_2$ symmetry, with realizations in lattice models.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
38 pages, 5 figures
Reconstructive martensitic phase transitions: intermittency, anti-trasformation, plasticity, irreversibility
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Edoardo Arbib, Noemi Barrera, Paolo Biscari, Giovanni Zanzotto
We study the mechanics of temperature-driven reconstructive martensitic transformations in crystalline materials, within the framework of nonlinear elasticity theory. We focus on the prototypical case of the square-hexagonal transition in 2D crystals, using a modular Ericksen-Landau-type strain energy whose infinite and discrete invariance group originates from the full symmetry of the underlying lattice. In the simulation of quasi-static thermally-driven transitions we confirm the role of the valley-floor network in establishing the strain-field transition-pathways on the symmetry-moulded strain energy landscape of the crystal. We also observe the phase change to progress through abrupt microstructure reorganization via strain avalanching under the slow driving. We reveal at the same time the presence of assisting anti-transformation activity, which locally goes against the overall transition course. Both transformation and anti-transformation avalanches exhibit Gutenberg-Richter like heavy-tailed size statistics. A parallel analysis shows agreement of these numerical results with their counterparts in empirical observations on temperature-induced martensitic transformations. The simulation furthermore shows that, in the present case of a reconstructive transformation, strain avalanching mostly involves lattice-invariant shears (LIS). As a consequence, microstructure evolution is accompanied by slip-induced defect nucleation and movement in the lattice. LIS activity also leads to the development of polycrystal grain-like lattice-homogeneity domains exhibiting high boundary segmentation in the body. All these effects ultimately lead to transformation irreversibility.
Materials Science (cond-mat.mtrl-sci)
20 pages, 5 figures, in print in the Journal of Applied Mechanics
Exploring Three-Atom-Thick Gold Structures as a Benchmark for Atomic-Scale Calibration of Break-Junction Systems
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
J.P. Cuenca, T. de Ara, A. Martinez-Garcia, E. Guzman, C. Sabater
We present an in-depth study of electronic transport in atomic-sized gold contacts using Break-Junction (BJ) techniques under cryogenic and ambient conditions. Our experimental results, supported by classical molecular dynamics (CMD) simulations and ab initio calculations, provide compelling evidence for the formation of three-atom-thick structures in gold nanocontacts under tensile stress. These findings extend previous studies that confirmed the existence of one- and two-atom-thick chains. Beyond identifying these novel atomic configurations, we introduce a fast and robust calibration method for Break-Junction systems, leveraging the characteristic length of these structures to convert piezo displacement into absolute distance in angstroms. Our approach presents a novel and robust method for calibrating atomic distances in atomic conductor systems at both cryogenic and room temperatures. The results also enable the assessment of electrode sharpness, even at room conditions.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
12 figures,11 pages
Particle Trajectory Prediction in Discrete Element Simulations using a Graph-Based Interaction-Aware Model
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Abhishek Setty, Lukas Morand, Poojitha Ramachandra, Claas Bierwisch
This study explores the applicability of a graph-based interaction-aware trajectory prediction model, originally developed for the transportation domain, to forecast particle trajectories in three-dimensional discrete element simulations. The model and our enhancements are validated at two typical particle simulation use cases: (i) particle flow in a representative unit cell with periodic boundary conditions (PBCs) in combination with sinusoidal velocity profile and (ii) shear flow in a representative unit cell with Lees\texttt{-}Edwards boundary conditions (LEBCs). For the models to learn the particle behavior subjected to these boundary conditions requires additional data transformation and feature engineering, which we introduce. Furthermore, we introduce and compare two novel training procedures for the adapted prediction model, which we call position\texttt{-}centric training (PCT) and velocity\texttt{-}centric training (VCT). The results show that the models developed for the transportation domain can be adapted to learn the behavior of particles in discrete element simulations.
Materials Science (cond-mat.mtrl-sci)
Robust and tunable oxide nanoscrolls for solar-driven H$_2$ generation and storage
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Hydrogen gas is a promising alternative to fossil fuels due to its high energy output and environmentally safe byproducts. Various morphologies of photocatalytic materials have been explored for high-efficiency H$_2$ production, for instance, quasi-1D nanoscroll structures that provide larger surface-to-volume ratio. Recently, we predicted layer-by-layer formation of stable oxide nanoscrolls directly from dichalcogenide precursors, eliminating the need for costly formation of two-dimensional oxides for a roll-up synthesis of nanoscrolls. In this study, we evaluate the suitability of those oxide nanoscroll materials MoO$_3$, WO$_3$, PdO$_2$, HfO$_2$, and GeO$_2$ for solar-driven photocatalytic H$_2$ production and storage. Using excited state theory simulations we discern their electronic properties as a function of interlayer scroll spacing and find them to possess electronic properties that are suitable for photocatalysis. Additionally, using ab initio molecular dynamics simulations we show that they are also suitable for H$_2$ storage as the nanoscrolls exhibit effective trapping of hydrogen, even in the presence of defects and vacancies in the oxides. This work thus demonstrates the discovery of robust and tunable oxide nanoscrolls as novel materials for advancing solar-driven hydrogen technologies.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Computational Physics (physics.comp-ph)
A Study of Superconducting Behavior in Ruthenium Thin Films
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
Bernardo Langa Jr., Brooke Henry, Ivan Lainez, Richard Haight, Kasra Sardashti
Ruthenium (Ru) is a promising candidate for the next-generation of electronic interconnects due to its low resistivity, small mean free path, and superior electromigration reliability at nanometer scales. Additionally, Ru exhibits superconductivity below 1 K, with resistance to oxidation, low diffusivity, and a small superconducting gap, making it a potential material for superconducting qubits and Josephson Junctions. Here, we investigate the superconducting behavior of Ru thin films (11.9 - 108.5 nm thick), observing transition temperatures from 657.9 mK to 557 mK. A weak thickness dependence appears in the thinnest films, followed by a conventional inverse thickness dependence in thicker films. Magnetotransport studies reveal type-II superconductivity in the dirty limit ({\xi} >> l), with coherence lengths ranging from 13.5 nm to 27 nm. Finally, oxidation resistance studies confirm minimal RuOx growth after seven weeks of air exposure. These findings provide key insights for integrating Ru into superconducting electronic devices.
Superconductivity (cond-mat.supr-con), Quantum Physics (quant-ph)
8 pages, 5 figures
Accuracy and capacity of Modern Hopfield networks with synaptic noise
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-04 20:00 EST
Sharba Bhattacharjee, Ivar Martin
We study the retrieval accuracy and capacity of modern Hopfield networks of with two-state (Ising) spins interacting via modified Hebbian $n$-spin interactions. In particular, we consider systems where the interactions deviate from the Hebb rule through additive or multiplicative noise or through clipping or deleting interactions. We find that the capacity scales as $N^{n-1}$ with the number of spins $N$ in all cases, but with a prefactor reduced compared to the Hebbian case. For $n=2$ our results agree with the previously known results for the conventional $n = 2$ Hopfield network.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
24 pages, 9 figures
Current-driven collective control of helical spin texture in van der Waals antiferromagnet
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Kai-Xuan Zhang, Suik Cheon, Hyuncheol Kim, Pyeongjae Park, Yeochan An, Suhan Son, Jingyuan Cui, Jihoon Keum, Joonyoung Choi, Younjung Jo, Hwiin Ju, Jong-Seok Lee, Youjin Lee, Maxim Avdeev, Armin Kleibert, Hyun-Woo Lee, Je-Geun Park
Electrical control of quantum magnetic states is essential in spintronic science. Initial studies on the ferromagnetic state control were extended to collinear antiferromagnets and, more recently, noncollinear antiferromagnets. However, electrical control mechanisms of such exotic magnetic states remain poorly understood. Here, we report the first experimental and theoretical example of the current control of helical antiferromagnets, arising from the competition between collinear antiferromagnetic exchange and interlayer Dzyaloshinskii-Moriya interaction in new van-der-Waals (vdW) material Ni1/3NbS2. Due to the intrinsic broken inversion symmetry, an in-plane current generates spin-orbit torque that, in turn, interacts directly with the helical antiferromagnetic order. Our theoretical analyses indicate that a weak ferromagnetic order coexists due to the Dzyaloshinskii-Moriya interaction, mediating the spin-orbit torque to collectively rotate the helical antiferromagnetic order. Our Ni1/3NbS2 nanodevice experiments produce current-dependent resistance change consistent with the theoretical prediction. This work widens our understanding of the electrical control of helical antiferromagnets and promotes vdW quantum magnets as interesting material platforms for electrical control.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Applied Physics (physics.app-ph), Quantum Physics (quant-ph)
Accepted by Physical Review Letters; 41 pages, 4 main figures, 12 supporting figures
Physical Review Letters XX, XXXX (2025)
Pressure Tuning of Layer-hybridized Excitons in Trilayer WSe2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Xuan Zhao, Jing Song, Wenqi Xiong, Qianying Hu, Yuxuan Song, Xin He, Tianzhong Yang, Song Liu, Shengjun Yuan, Hongyi Yu, Yang Xu
We demonstrate dynamic pressure tuning (0-6.6 GPa) of layer-hybridized excitons in AB-stacked trilayer WSe$_2$ via diamond-anvil-cell-integrated reflectance spectroscopy. Pressure-controlled interlayer coupling manifests in enhanced energy-level anti-crossings and oscillator strength redistribution, with Stark shift analysis revealing a characteristic dipole moment reduction of 11%. Notably, the hybridization strength between the intra- and interlayer excitons triples from $\sim$10 meV to above $\sim$30 meV, exhibiting a near-linear scaling of 3.5$\pm$0.2 meV/GPa. Spectral density simulations resolve four distinct components, i.e., intralayer ground/excited and interlayer ground/excited excitons, with their relative weights transitioning from one component dominant to strongly hybridized at higher pressures. Our findings highlight the potential for controlling excitonic properties and engineering novel optoelectronic devices through interlayer compression.
Materials Science (cond-mat.mtrl-sci)
6 pages, 4 figures
Exploring 2D/Quasi-2D Ruddlesden-Popper Perovskite A$_{n+1}$Hf$n$S${3n+1}$ (A = Ca, Sr, and Ba; n = 1-3) for Optoelectronics using Many-Body Perturbation Theory
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Surajit Adhikari, Aksaj Bharatwaj, Priya Johari
Dimensionality engineering in A${n+1}$B$n$X${3n+1}$ Ruddlesden-Popper (RP) perovskite phases has emerged as a promising strategy to enhance optoelectronic properties. These properties are highly material-dependent, requiring detailed exploration of electronic, optical, excitonic, transport, and polaronic characteristics. However, the absence of comprehensive studies continues to impede the rational design of high-performance materials. In this work, we investigate the excitonic and polaronic effects in A${n+1}$Hf$n$S${3n+1}$ (A = Ca, Sr, and Ba; n = 1-3) RP phases, examining their relative stability and optoelectronic properties using several first-principles based methodologies within the framework of density functional theory and many-body perturbation theory (GW and BSE). Our study suggests that these compounds are mechanically stable and feature G$_0$W$_0$@PBE bandgaps ranging from 1.43 to 2.14 eV, which are smaller than those of their bulk counterparts. BSE and model-BSE (mBSE) calculations indicate that these RP phases display notable optical anisotropy, with the exciton binding energy decreasing as the thickness of the perovskite layer increases. In addition, intermediate to strong carrier-phonon scattering is observed in these compounds, confirmed through the Fröhlich mechanism near room temperature. Using the Feynman polaron model, the polaron parameters of these RP phases are also computed, and it is found that charge-separated polaronic states are less stable than bound excitons. Finally, a significant increase in electron mobilities is observed in RP phases compared to their bulk counterparts. Overall, the insights gained from this study will enable the rational design of layered perovskite phases for applications in solar cells and other optoelectronic devices.
Materials Science (cond-mat.mtrl-sci)
11 pages, 3 figures, 6 tables
Role of seed layer in growing atomically flat TiTe2/Sb2Te3 heterostructure thin films at the wafer scale
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Chao Nie, Xueyang Shen, Junying Zhang, Chenyu Wen, Yuxin Du, Yazhi Xu, Riccardo Mazzarello, En Ma, Xiaozhe Wang, Wei Zhang, Jiang-Jing Wang
Chalcogenide phase-change materials (PCMs) are a leading candidate for advanced memory and computing applications. Epitaxial-like growth of chalcogenide thin films at the wafer scale is important to guarantee the homogeneity of the thin film but is challenging with magnetron sputtering, particularly for the growth of phase-change heterostructure (PCH), such as TiTe2/Sb2Te3. In this work, we report how to obtain highly textured TiTe2/Sb2Te3 heterostructure thin films with atomically sharp interfaces on standard silicon substrates. By combining atomic-scale characterization and ab initio simulations, we reveal the critical role of the Sb2Te3 seed layer in forming a continuous Si-Sb-Te mixed transition layer, which provides a wafer-scale flat surface for the subsequent epitaxial-like growth of TiTe2/Sb2Te3 thin film. By gradually reducing the thickness of the seed layer, we determine its critical limit to be ~2 nm. Non-negligible in-plane tensile strain was observed in the TiTe2 slabs due to the lattice mismatch with the adjacent Sb2Te3 ones, suggesting that the chemical interaction across the structural gaps in the heterostructure is stronger than a pure van der Waals interaction. Finally, we outline the potential choices of chalcogenides for atomically flat seed layers on standard silicon substrates, which can be used for wafer-scale synthesis of other high-quality PCM or PCH thin films.
Materials Science (cond-mat.mtrl-sci)
17 pages, 8 figures
Cryogen-free low-temperature photoemission electron microscopy for high-resolution nondestructive imaging of electronic phases
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Chen Wang, Shaoshan Wang, Chuan Guo, Chengjian Yu, Qi Fu, Xiaopeng Xie, Changxi Zheng
Quantum materials exhibit phases such as superconductivity at low temperatures, yet imaging their phase transition dynamics with high spatial resolution remains challenging due to conventional tools’ limitations - scanning tunneling microscopy offers static snapshots, while transmission electron microscopy lacks band sensitivity. Photoemission electron microscopy (PEEM) can resolve band structures in real/reciprocal spaces rapidly, but suffering from insufficient resolution for (near)atomic-scale quantum physics due to the unstable cooling designs. Here, we developed cryogen-free low-temperature PEEM (CFLT-PEEM) achieving 21.1 K stably. CFLT-PEEM attains a record-breaking resolution of 4.48 nm without aberration correction, enabling direct visualization of surface-state distribution characteristics along individual atomic steps. The advancement lies in narrowing the segment of band structures for imaging down to 160 meV, which minimizes the chromatic aberration of PEEM. CFLT-PEEM enables rapid, nondestructive high-resolution imaging of cryogenic electronic structures, positioning it as a powerful tool for physics and beyond.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
This submission is a single PDF file containing the main text and Supplementary Information. The document is 23 pages long and includes 12 figures. The Supplementary Information begins on page 15
Zeeman split Kramers doublets in spin-supersolid candidate Na${2}$BaCo(PO${4}$)$_{2}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
T. I. Popescu, N. Gora, F. Demmel, Z. Xu, R. Zhong, T. J. Williams, R. J. Cava, G. Xu, C. Stock
Na${2}$BaCo(PO${4}$)${2}$ is a triangular antiferromagnet that displays highly efficient adiabatic demagnetization cooling (J. Xiang $\textit{et al.}$ Nature ${\bf{625}}$, 270 (2024)) near a quantum critical point at $\mu{0}H_{c}\sim 1.6$ T, separating a low-field magnetically disordered from a high-field fully polarized ferromagnetic phase. We apply high resolution backscattering neutron spectroscopy in an applied field to study the magnetic excitations near $\mu_{0}H_{c}$. At large fields we observe ferromagnetic fluctuations that gradually transition to being overdamped in energy below $\mu_{0}H_{c}$ where the magnetism is spatially disordered. We parameterize the excitations in the high field polarized phase in terms of coupled Zeeman split Kramers doublets originating from the presence of spin-orbit coupling. On reducing the field, the splitting between the Kramers doublets is reduced and if done adiabatically, provides a mechanism for reducing temperature. On lowering the applied field through the $\mu_{0}H_{c}$ the excitations characterize a textured phase that we suggest is inefficient for cooling. Low temperature disordered frustrated magnets built on Kramers doublets with nearby quantum critical points provide a route for efficient magnetocalorics.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
(main text - 5 pages, 4 figures; supplementary information - 7 pages, 7 figures, to be published in Physical Review Letters)
Theoretical Exploration of Phase Transitions in a Cavity-BEC System with Two Crossed Optical Pumps
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Wei Qin, Dong-Chen Zheng, Zhao-Di Wu, Yuan-Hong Chen, Renyuan Liao
We consider a Bose-Einstein condensation (BEC) inside an optical cavity and two crossed coherent pump fields. We determine the phase boundary separating the normal superfluid phase and the superradiance phase, perturbatively. In the regime of negative cavity detuning, we map out the phase diagrams both for an attractive and a repulsive optical lattice. It turns out that the situation is quite different in two cases. Specifically, in the case of attractive lattice, if a system is in the superradiant phase with one pump laser, adding another pump does not drive the system out of the superradiance phase. While for the repulsive lattice, increasing another pump potential have suppressive effects on the superradiance. We also find that, in the case of attractive lattice, equally increasing two pump lattice potentials can induce a transition from the normal phase to the superradiance phase. In stark contrast, for the repulsive lattice, the system will remain in the normal phase as the pump depths are tuned within a wide range, independent of the cavity detuning and the decay rate.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
7 pages; 6 figures
Phys. Rev. A 109, 013310 (2024)
Mediated Interactions and Damping Effects in Superfluid Mixtures of Bose and Fermi Gases
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Dong-Chen Zheng, Yu-Xin Liao, Wen Lin, Renyuan Liao
We investigate the homogeneous superfluid mixtures of Bardeen-Cooper-Schrieffer~(BCS) superfluid originating from pairing two-species fermionic atoms and superfluidity stemming from condensation of bosonic atoms. By integrating out the freedoms associated with the BCS superfluid, we derive the fermion-mediated interactions between bosons, which is attractive and can be tuned from long range in the BCS region to short range in the region of Bose-Einstein condensation (BEC) of molecular dimers. By analyzing the Bogoliubov spectrum and the damping rate of bosonic superfluid, we map out the phase diagram spanned by the boson-fermion mass ratio and the boson-fermion coupling strength, which consists of a phase separation region and two phase mixing regions with and without Landau damping. The three different phases can coexist at a tricritical point, which moves toward low boson-fermion mass ratio and high boson-fermion scattering length as the fermion-fermion interaction strength is tuned up on the BCS side.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
7 pages, 5 figures
Phys. Rev. A 109, 023327 (2024)
Condensation energy of superconducting BEC of non-interacting Cooper pairs in multilayers
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
I. Chávez, P. Salas, J.J. Valencia, M.A. Solís
Boson-Fermion models of superconductivity are getting attention as they are able to explain some of the high temperature superconductor’s properties. Here we report on the condensation energy of a 3D non-interacting mixture of paired fermions (electrons) as Cooper pairs assumed to be composite bosons, which are responsible for carrying superconductivity, plus unpaired fermions both trapped in a periodic multilayer structure like that of the cuasi-two dimensional High-Temperature superconductor planes, generated by applying an external Dirac’s comb potential in the direction perpendicular to the planes where superconductivity preferably occurs, while in the other two directions parallel to the planes the mixture moves freely. For bosons we give the Bose-Einstein condensation critical temperature, which we assume is equal to the superconducting critical one, while for both bosons and fermions we give the chemical potential, the internal energy and the entropy, all of them as functions of temperature, in order to calculate the Helmholtz free energy, which we use to obtain the condensation energy of a mixture of $N_F$ ideal fermions (electrons), which after turning on the attractive pair interaction become $N_B = N_{F}/2$ ideal bosons. For several plane impenetrability magnitudes, we calculate the condensation energy as the difference between the free energies of the fermions which are in the normal state minus that of the bosons in the condensed state, where we observe that as the plane impenetrability increases: the condensation energy increases; the critical temperature decreases, as expected for example for cuprate superconductors, and the behavior of the entropy and the internal energy show a dimensional crossover from 3D to 2D.
Superconductivity (cond-mat.supr-con)
Air-stable lithiation engineering of $\mathrm{MoS}_{2}$ for direct-bandgap multilayers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Qi Fu, Yichi Zhang, Jichuang Shen, Siyuan Hong, Jie Wang, Chen Wang, Jingyi Shen, Wei Kong, Guolin Zheng, Jun Yan, Jie Wu, Changxi Zheng
Due to its sizable direct bandgap and strong light-matter interactions, the preparation of monolayer $\mathrm{MoS}{2}$ has attracted significant attention and intensive research efforts. However, multilayer $\mathrm{MoS}{2}$ is largely overlooked because of its optically inactive indirect bandgap caused by interlayer coupling. It is highly desirable to modulate and decrease the interlayer coupling so that each layer in multilayer $\mathrm{MoS}{2}$ can exhibit a monolayer-like direct-gap behavior. Here, we demonstrate the nanoprobe fabrication of $\mathrm{Li}{x}\mathrm{MoS}{2}$-based multilayers exhibiting a direct bandgap and strong photoluminescence emission from tightly bound excitons and trions. The fabrication is facilitated by our newly developed Li-ion platform, featuring tip-induced Li intercalation, air stability and rewritability. Raman characterizations reveal that controlled Li intercalation effectively transforms multilayer $\mathrm{MoS}{2}$ into the stack of multiple monolayers, leading to a 26-fold enhancement of photoluminescence, compared to a monolayer. This intercalation result is different from existing observations of transforming $\mathrm{MoS}_{2}$ multilayers into metallic phases.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Field-driven band asymmetry and non-reciprocal transport in a helimagnet
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Darius-Alexandru Deaconu, Aneesh Agarwal, Rodion Vladimirovich Belosludov, Robert-Jan Slager, Mohammad Saeed Bahramy
Helimagnets exhibit noncollinear spin arrangements characterized by a periodic helical modulation, giving rise to emergent chiral properties. These materials have attracted significant interest due to their potential applications in spintronics, particularly for robust information storage and the realization of topological spin textures such as skyrmions. In this work, we focus on Yoshimori-type helimagnets, where competing exchange interactions mediated by conduction electrons stabilize helical spin structures without requiring Dzyaloshinskii-Moriya interaction. We introduce a minimal model describing the electronic structure of a one-dimensional helimagnet in the presence of an external magnetic field and investigate its impact on non-reciprocal transport. We demonstrate how band asymmetry emerges in the conical phase induced by the external field, leading to a nonzero second-order electronic conductivity and injection photoconductivity. Our results provide insight into the interplay between the real space magnetic texture and electronic properties, paving the way for future studies on chirality-driven transport phenomena in centrosymmetric helimagnets.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
4 figures, Supplementary Material included
Magnetic order and spin dynamics across the ferromagnetic quantum critical point in Ni\boldmath{${1-x}$}Mo\boldmath{${x}$}
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
H. K. Dara, S. S. Islam, A. Magar, D. Patra, H. Luetkens, T. Shiroka, R. Nath, D. Samal
Realizing a quantum critical point (QCP) in clean ferromagnetic (FM) metals has remained elusive due to the coupling of magnetization to the electronic soft modes that drive the transition to be of first order. However, by introducing a suitable amount of quenched disorder, one can still establish a QCP in ferromagnets. In this study, we ascertain that the itinerant ferromagnet Ni${1-x}$Mo${x}$ exhibits a FM QCP at a critical doping of $x_c \simeq 0.125$. Through magnetization and muon-spin relaxation measurements, we demonstrate that the FM ordering temperature is suppressed continuously to zero at $x_c$, while the magnetic volume fraction remains $100%$ up to $x_c$, indicating a second-order phase transition. The QCP is accompanied by a non-Fermi liquid behavior, as evidenced by the logarithmic divergence of the specific heat and the linear temperature dependence of the low-temperature resistivity. Our findings reveal a minimal effect of disorder on the critical spin dynamics of Ni${1-x}$Mo${x}$ at $x_c$, highlighting it as one of the rare systems to exhibit a clean FM QCP.
Strongly Correlated Electrons (cond-mat.str-el)
Theoretical and Experimental Investigations of High-Performance Sr2CoNbO6-delta Double Perovskite for IT-SOFC Cathode Applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Jyotsana Kalaa, Vicky Dhongde, Suddhasatwa Basu, Brajesh Kumar Mani, M. Ali Haider
Enhancing the transport of oxygen anions in the cathode while maintaining surface stability is essential for improving the performance of intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study investigates a novel cathode material candidate, Sr2CoNbO6-delta (SCNO), using density functional theory, molecular dynamics, and experimental characterization. The redox active Co cation at B-site and less reducible Nb cation at the B’-site together enhance both surface stability and electrocatalytic performance. SCNO is observed to have a higher concentration of oxygen vacancies and increased oxygen diffusivity on the surface. The surface stability of SCNO is further improved when simulated under compressive strain due to the GDC electrolyte substrate. These findings offer new insights into controlling Sr segregation in SCNO, contributing to a better understanding of its enhanced oxygen reduction reaction (ORR) activity and high surface stability. Subsequently, SCNO was synthesized to evaluate its potential as a cathode material in SOFCs. To assess its performance, symmetric cells with uniform dense thin films of varying thicknesses (40 and 80 nm) were fabricated using the pulsed laser deposition technique. Electrochemical impedance spectroscopy and distributed relaxation time analysis indicate that bulk oxygen ion diffusion is a limiting factor for the ORR in SCNO. The polarization resistance for the 40 and 80 nm dense thin film symmetric cells ranged between 0.329 - 0.241 ohm cm2 and 1.095 - 0.438 ohm cm2, respectively, within the temperature range of 773 - 973 K in an air atmosphere. The full cell configuration of NiO-GDC|GDC|SCNO demonstrated a significantly high peak power density of 0.633 W/cm2 at 973 K. This theory-guided design and experimental study suggest that SCNO is a promising candidate for IT-SOFC cathode materials.
Materials Science (cond-mat.mtrl-sci)
31 pages, 9 figures, 4 tables
The Dynamics in Vibro-fluidized Beds: A Diffusing Wave Spectroscopy Study
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Marlo Kunzner, Christopher Mayo, Matthias Sperl, Jan Philipp Gabriel
We demonstrate the densification of a granular model system of polystyrene spheres over time by shaking with varying excitation amplitudes or effective temperatures. This densification is quantified by the mean square displacement (MSD), which is measured by diffuse wave spectroscopy (DWS) of a sinusoidally excited vibrating fluidized granular bed. The DWS method also extracts the inherent heterogeneous dynamics of the system in the bulk and at the wall. Through an empirical model-based extraction we obtain the ballistic and diffusive time constants, as well as caging sizes, which were found to depend on temperature and density. The results obtained from this study reveal a sub-diffusive power-law behavior in the MSD, indicating an arrest of motion and potentially a glassy system, especially in cases where the excitation is low to moderate compared to gravity. The extracted MSD caging sizes are two orders smaller than the Lindeman length found in colloidal systems.
Soft Condensed Matter (cond-mat.soft)
Roadmap on Nonlocality in Photonic Materials and Metamaterials
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Francesco Monticone, N. Asger Mortensen, Antonio I. Fernández-Domínguez, Yu Luo, Christos Tserkezis, Jacob B. Khurgin, Tigran V. Shahbazyan, André J. Chaves, Nuno M. R. Peres, Gino Wegner, Kurt Busch, Huatian Hu, Fabio Della Sala, Pu Zhang, Cristian Ciracì, Javier Aizpurua, Antton Babaze, Andrei G. Borisov, Xue-Wen Chen, Thomas Christensen, Wei Yan, Yi Yang, Ulrich Hohenester, Lorenz Huber, Martijn Wubs, Simone De Liberato, P. A. D. Gonçalves, F. Javier García De Abajo, Ortwin Hess, Illya Tarasenko, Joel D. Cox, Line Jelver, Eduardo J. C. Dias, Miguel Sánchez Sánchez, Dionisios Margetis, Guillermo Gómez-Santos, Tobias Stauber, Sergei Tretyakov, Constantin Simovski, Samaneh Pakniyat, J. Sebastián Gómez-Díaz, Igor V. Bondarev, Svend-Age Biehs, Alexandra Boltasseva, Vladimir M. Shalaev, Alexey V. Krasavin, Anatoly V. Zayats, Andrea Alù, Jung-Hwan Song, Mark L. Brongersma, Uriel Levy, Olivia Y. Long, Cheng Guo, Shanhui Fan, Sergey I. Bozhevolnyi, Adam Overvig, Filipa R. Prudêncio, Mário G. Silveirinha, S. Ali Hassani Gangaraj, Christos Argyropoulos, Paloma A. Huidobro, Emanuele Galiffi, Fan Yang, John B. Pendry, David A. B. Miller
Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally made in optical material modeling. On one end, the growing interest in plasmonic, polaritonic and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials–metamaterials and metasurfaces–can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In the case of metasurfaces, in particular, nonlocality engineering has become a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward–toward new scientific discoveries and technological advancements.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Is directed percolation class for synchronization transition robust with multi-site interactions?
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Manoj C. Warambhe, Prashant M. Gade
Coupled map lattice with pairwise local interactions is a well-studied system. However, in several situations, such as neuronal or social networks, multi-site interactions are possible. In this work, we study the coupled Gauss map in one dimension with 2-site, 3-site, 4-site and 5-site interaction. This coupling cannot be decomposed in pairwise interactions. We coarse-grain the variable values by labeling the sites above $x^{\star}$ as up spin (+1) and the rest as down spin (-1) where $x^{\star}$ is the fixed point. We define flip rate $F(t)$ as the fraction of sites $i$ such that $s_{i}(t-1) \neq s_{i}(t)$ and persistence $P(t)$ as the fraction of sites $i$ such that $s_{i}(t’)=s_{i}(0)$ for all $t’ \le t$. The dynamic phase transitions to a synchronized state is studied above quantifiers. For 3 and 5 sites interaction, we find that at the critical point, $F(t) \sim t^{-\delta}$ with $\delta=0.159$ and $P(t) \sim t^{-\theta}$ with $\theta=1.5$. They match the directed percolation (DP) class. Finite-size and off-critical scaling is consistent with DP class. For 2 and 4 site interactions, the exponent $\delta$ and behavior of $P(t)$ at critical point changes. Furthermore, we observe logarithmic oscillations over and above power-law decay at the critical point for 4-site coupling. Thus multi-site interactions can lead to new universality class(es).
Statistical Mechanics (cond-mat.stat-mech)
17 pages, 31 figures
Tailoring of charge carriers with deposition temperature in pulsed laser deposited BiFeO3 thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Viswajit R S, Jinesh K.B, Ashok K
This research investigates the structural, topological, electrical and optical properties of pulsed laser deposited polycrystalline BiFeO3 thin films on silicon and glass substrate at varying deposition temperatures ranging from 400 degC to 700 degC. X-ray diffraction confirm rhombohedral phase and X-ray photoelectron spectroscopy reveals stoichiometric BiFeO3 films. The optical bandgap of thin films obtained from absorption spectra increases with the substrate temperature. Photoluminescence emission spectrum reveals the defects and Atomic Force Microscopy analysis bring out the surface topography and crystallinity improvement with temperature. The charge transport studies reveal a transition in conductivity from n-type at lower deposition temperature to p-type at higher deposition temperature, attributed to oxygen and bismuth vacancies respectively. The intricate understanding of conductivity tuning and the leaky nature of BiFeO3 thin film opens avenues for applications in nonvolatile memories, particularly neuromorphic devices.
Materials Science (cond-mat.mtrl-sci)
Applied Surface Science 661 (2024) 160016
Modelling the non-linear viscoelastic behaviour of brain tissue in torsion
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
G. Small, F. Ballatore, C. Giverso, V. Balbi
Brain tissue accommodates non-linear deformations and exhibits time-dependent mechanical behaviour. The latter is one of the most pronounced features of brain tissue, manifesting itself primarily through viscoelastic effects such as stress relaxation. To investigate its viscoelastic behaviour, we performed ramp-and-hold relaxation tests in torsion on freshly slaughtered cylindrical ovine brain samples ($25,,\text{mm}$ diameter and $\sim 10,,\text{mm}$ height). The tests were conducted using a commercial rheometer at varying twist rates of ${40,240,400},,\text{rad},,\text{m}^{-1},,\text{s}^{-1}$, with the twist remaining fixed at $\sim 88,,\text{rad},,\text{m}^{-1}$, which generated two independent datasets for torque and normal force. The complete set of viscoelastic material parameters was estimated via a simultaneous fit to the analytical expressions for the torque and normal force predicted by the modified quasi-linear viscoelastic model. The model’s predictions were further validated through finite element simulations in FEniCS. Our results show that the modified quasi-linear viscoelastic model – recently reappraised and largely unexploited – accurately fits the experimental data. Moreover, the estimated material parameters are in line with those obtained in previous studies on brain samples under torsion. When coupled with bespoke finite element models, these material parameters could enhance our understanding of the forces and deformations involved in traumatic brain injury and contribute to the design of improved headgear for sports such as boxing and motorsports. On the other hand, our novel testing protocol offers new insights into the mechanical behaviour of soft tissues other than the brain.
Soft Condensed Matter (cond-mat.soft)
19 pages, 11 figures
Correlated hopping induced topological order in an atomic mixture
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Ashirbad Padhan, Luca Barbiero, Tapan Mishra
The large majority of topological phases in one dimensional many-body systems are known to inherit from the corresponding single-particle Hamiltonian. In this work, we go beyond this assumption and find a new example of topological order induced through specific interactions couplings. Specifically, we consider a fermionic mixture where one component experiences a staggered onsite potential and it is coupled through density dependent hopping interactions to the other fermionic component. Crucially, by varying the sign of the staggered potential, we show that this latter fermionic component can acquire topological properties. Thanks to matrix product state simulations, we prove this result both at the equilibrium by extracting the behavior of correlation functions and in an out-of-equilibrium scheme by employing a Thouless charge pumping. Notably, we further discuss how our results can be probed in quantum simulators made up of ultracold atoms. Our results reveal an important and alternative mechanism that can give rise to topological order.
Quantum Gases (cond-mat.quant-gas)
5 pages, 4 figures
Statistical Mechanics of Semantic Compression
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-04 20:00 EST
The basic problem of semantic compression is to minimize the length of a message while preserving its meaning. This differs from classical notions of compression in that the distortion is not measured directly at the level of bits, but rather in an abstract semantic space. In order to make this precise, we take inspiration from cognitive neuroscience and machine learning and model semantic space as a continuous Euclidean vector space. In such a space, stimuli like speech, images, or even ideas, are mapped to high-dimensional real vectors, and the location of these embeddings determines their meaning relative to other embeddings. This suggests that a natural metric for semantic similarity is just the Euclidean distance, which is what we use in this work. We map the optimization problem of determining the minimal-length, meaning-preserving message to a spin glass Hamiltonian and solve the resulting statistical mechanics problem using replica theory. We map out the replica symmetric phase diagram, identifying distinct phases of semantic compression: a first-order transition occurs between lossy and lossless compression, whereas a continuous crossover is seen from extractive to abstractive compression. We conclude by showing numerical simulations of compressions obtained by simulated annealing and greedy algorithms, and argue that while the problem of finding a meaning-preserving compression is computationally hard in the worst case, there exist efficient algorithms which achieve near optimal performance in the typical case.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Computation and Language (cs.CL), Neurons and Cognition (q-bio.NC)
20 pages (including appendix), 3 figures
Flowing menisci: coupled dynamics and liquid exchange with soap films
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Alexandre Vigna-Brummer, Antoine Monier, Isabelle Cantat, Christophe Brouzet, Christophe Raufaste
Liquid foams exhibit menisci whose lengths range from hundreds of microns in microfoams to several centimeters in macroscopic bubble arrangements. These menisci thin under gravity until reaching a steady thickness profile, where hydrostatic and capillary pressures are balanced. While these menisci are in contact with soap films, dynamical liquid exchanges between them are neglected in current drainage models, which assume thin films provide a negligible liquid reservoir. Using controlled experiments, we systematically measure the shape of an isolated meniscus placed in a vertical soap film. By increasing the film thickness, we identify a flowing regime in which the flux from the adjacent film significantly enlarges the meniscus. We present an analytical model that extends the drainage equation to incorporate this film flux and introduce a gravito-exchange length, which sets the minimum meniscus thickness. The model is in quantitative agreement with experiments, capturing the transition between hydrostatic and flowing menisci. This study has implications for flowing or rearranging foams, where thick films are commonly observed.
Soft Condensed Matter (cond-mat.soft), Fluid Dynamics (physics.flu-dyn)
7 pages, 5 figures, 1 supplementary material, 3 supplementary videos
Topological phenomena in artificial quantum materials revealed by local Chern markers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Catalin D. Spataru, Wei Pan, Alexander Cerjan
A striking example of frustration in physics is Hofstadter’s butterfly, a fractal structure that emerges from the competition between a crystal’s lattice periodicity and the magnetic length of an applied field. Current methods for predicting the topological invariants associated with Hofstadter’s butterfly are challenging or impossible to apply to a range of materials, including those that are disordered or lack a bulk spectral gap. Here, we demonstrate a framework for predicting a material’s local Chern markers using its position-space description and validate it against experimental observations of quantum transport in artificial graphene in a semiconductor heterostructure, inherently accounting for fabrication disorder strong enough to close the bulk spectral gap. By resolving local changes in the system’s topology, we reveal the topological origins of antidot-localized states that appear in artificial graphene in the presence of a magnetic field. Moreover, we show the breadth of this framework by simulating how Hofstadter’s butterfly emerges from an initially unpatterned 2D electron gas as the system’s potential strength is increased, and predict that artificial graphene becomes a topological insulator at the critical magnetic field. Overall, we anticipate that a position-space approach to determine a material’s Chern invariant without requiring prior knowledge of its occupied states or bulk spectral gaps will enable a broad array of fundamental inquiries and provide a novel route to material discovery, especially in metallic, aperiodic, and disordered systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
8 pages, 4 figures, supplemental materials. In press at Phys. Rev. Lett
Relativistic Spin-Lattice Interaction Compatible with Discrete Translation Symmetry in Solids
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Bumseop Kim, Noejung Park, Kyoung-Whan Kim
Recent interest in orbital angular momentum has led to a rapid expansion of research on spin-orbit coupling effects in solids, while also highlighting significant technical challenges. The breaking of rotational symmetry renders the orbital angular momentum operator ill-defined, causing conceptual and computational issues in describing orbital motion. To address these issues, here we propose an alternative framework. Based on the Bloch representation of the full relativistic interaction, we derive a field that directly couples to electron spins while preserving discrete translational symmetry, thereby eliminating the need for the position operator. Our approach is fully compatible with existing first-principles computational frameworks for both static and time-dependent density functional theory. We demonstrate that this method offers a more effective description of the Edelstein and spin Hall effects compared to conventional orbital angular momentum formalisms.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Two-dimensional transverse-field $XY$ model with the in-plane anisotropy and Dzyaloshinskii-Moriya interaction: Anisotropy-driven transition
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Yoshihiro Nishiyama (Okayama university)
The two-dimensional (2D) quantum spin-$S=1/2$ $XY$ model with the transverse-field $H$, in-plane-anisotropy $\gamma$, and Dzyaloshinskii-Moriya (DM) $D$ interactions was investigated by means of the exact diagonalization method, which enables us to treat the $D$-mediated complex-valued Hermitian matrix elements. According to the preceding real-space renormalization group analysis at $H=0$, the $\gamma$-driven phase transition occurs generically for $D\ne 0$ in contrast to the 1D $XY$ model where both $\gamma$- and $D$-induced phases are realized for $\gamma>D$ and $ \gamma <D$, respectively. In this paper, we evaluated the $\beta$ function $\beta(\gamma)$, namely, the differential of $\gamma$ with respect to the concerned energy scale, and from its behavior in proximity to $\gamma=0$, we observed an evidence of the $\gamma$-driven phase transition; additionally, $\gamma$’s scaling dimension is estimated from $\beta(\gamma)$’s slope. It was also determined how the value of the DM interaction influences the order-disorder phase boundary $H_c(\gamma)$ around the multi-critical point, $\gamma \to 0$.
Statistical Mechanics (cond-mat.stat-mech)
$\textit{In situ}$ time-resolved X-ray absorption spectroscopy of shock-loaded magnesiosiderite
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Anand Prashant Dwivedi, Jean-Alexis Hernandez, Sofia Balugani, Delphine Cabaret, Valerio Cerantola, Davide Comboni, Damien Deldicque, François Guyot, Marion Harmand, Harald Müller, Nicolas Sévelin-Radiguet, Irina Snigireva, Raffaella Torchio, Tommaso Vinci, Thibaut de Rességuier
Carbonate minerals are important in Earth’s system sciences and have been found on Mars and in meteorites and asteroids, highlighting the importance of impacts in planetary processes. While extensively studied under static compression, the behavior of carbonates under shock compression remains underexplored, with no $\textit{in situ}$ X-ray investigations reported so far. Here we investigate natural magnesiosiderite (Fe${0.6}$Mg${0.4}$CO$_{3}$) under nanosecond laser-driven shock compression at pressures up to 150 GPa, coupled with $\textit{in situ}$ ultrafast synchrotron X-ray absorption spectroscopy (XAS). The interpretation of the experimental spectra is complemented using first-principles absorption cross-section calculations performed on crystalline phases at different pressures and on a dense liquid phase obtained using density functional theory-based molecular dynamics (DFT-MD) simulations. Under laser-driven shock compression, the magnesiosiderite crystal phase remains unchanged up to the melt. Under shock reverberation, the absorption spectra show changes similar to those attributed to a high-spin to low-spin transition observed under static compression. At higher pressures, the laser shock induces the formation of CO$_4$ tetrahedral units in the melt. Upon unloading from the shocked state, only a few nanoseconds later, the original magnesiosiderite phase is recovered.
Materials Science (cond-mat.mtrl-sci), Geophysics (physics.geo-ph)
42 pages, 4 main text figures, 11 supplementary text figures
Possible quantum spin liquid state of CeTa$7$O${19}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
N. Li, A. Rutherford, Y. Y. Wang, H. Liang, Y. Zhou, Y. Sun, D. D. Wu, P. F. Chen, Q. J. Li, H. Wang, W. Xie, E. S. Choi, S. Z. Zhang, M. Lee, H. D. Zhou, X. F. Sun
CeTa$7$O${19}$ is a recently found two-dimensional triangular lattice antiferromagnet without showing magnetic order. We grew high-quality CeTa$7$O${19}$ single crystals and studied the low-temperature magnetic susceptibility, specific heat and thermal conductivity. The dc magnetic susceptibility and magnetization reveal its nature of effective spin-1/2, easy axis anisotropy, and antiferromagnetic spin coupling. The ultralow-temperature ac susceptibility and specific heat data indicate the absence of any phase transition down to 20 mK. The ultralow-temperature thermal conductivity ($\kappa$) at zero magnetic field exhibits a non-zero residual term $\kappa_0/T =$ 0.0056 W/K$^2$m. Although the magnetic field dependence of $\kappa$ is rather weak, the 14 T thermal conductivity shows an essential zero residual term. All these results point to a possible ground state of quantum spin liquid.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
8 pages, 6 figures, accepted for publication in Phys. Rev. B
A two-dimensional semiconductor-semimetal drag hybrid
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Yingjia Liu, Kaining Yang, Kenji Watanabe, Takashi Taniguchi, Wencai Ren, Zheng Vitto Han, Siwen Zhao
Lateral charge transport of a two-dimensional (2D) electronic system can be much influenced by feeding a current into another closely spaced 2D conductor, known as the Coulomb drag phenomenon – a powerful probe of electron-electron interactions and collective excitations. Yet the materials compatible for such investigations remain limited to date. Especially, gapped 2D semiconductors with inherently large correlations over a broad gate range have been rarely accessible at low temperatures. Here, we show the emergence of a large drag response (drag resistance $R_{\text{drag}}$ at the order of k$\Omega$, with a passive-to-active drag ratio up to $\sim$ 0.6) in a semiconductor-semimetal hybrid, realized in a graphene-MoS${2}$ heterostructure isolated by an ultrathin 3 nm hexagonal boron nitride (h-BN) dielectric. We observe a crossover of $T$ to $T^{2}$ dependence of $R{\text{drag}}$, separated by a characteristic temperature $T_{d} \sim E_{F}/k_{F}d$ ($d$ being the interlayer distance), in echo with the presence of a metal-insulator transition in the semiconducting MoS${2}$. Interestingly, the current nanostructure allows the decoupling of intralayer interaction-driven drag response by varying density in one layer with that in the other layer kept constant. A large Wigner-Seitz radius $r{s}$ ($>$ 10 within the density range of 1 to $4 \times 10^{12}~\mathrm{cm}^{-2}$) in the massive Schrödinger carriers in MoS$_{2}$ is thus identified to dominate the quadratic dependence of total carriers in the drag system, while the massless Dirac carriers in graphene induce negligible drag responses as a function of carrier density. Our findings establish semiconductor-semimetal hybrid as a platform for studying unique interaction physics in Coulomb drag systems.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 8 figures
Uniaxial Ordering by Self-Assembly of Isotropic Octahedral Junctions
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
We demonstrate that isotropic octahedral (sixfold branched) junctions with three diagonal endpoint pairs of different colors almost inevitably form a macroscopic assembly of uniaxial order, exhibiting the perfect order of a single color. Monte Carlo simulations of the antiferromagnetic three-state Potts model on the tripartite reo net, consisting of corner-sharing regular octahedrons, confirm this counterintuitive prediction, while showcasing switching self-assembly upon an ordering phase transition. The possible inequivalence of three directions, i.e., more symmetry breaking than uniaxiality, is found and discussed for the ordered phase of this model at finite temperatures. Some additional analyses of the model are provided, including the possibility of a metastable isotropic order, which aligns better with intuition.
Statistical Mechanics (cond-mat.stat-mech), Chemical Physics (physics.chem-ph)
23 pages, 11 figures
Electrical switching of Chern insulators in moire rhombohedral heptalayer graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Zhiyu Wang, Qianling Liu, Xiangyan Han, Zhuoxian Li, Wenjun Zhao, Zhuangzhuang Qu, Chunrui Han, Kenji Watanabe, Takashi Taniguchi, Zheng Vitto Han, Sicheng Zhou, Bingbing Tong, Guangtong Liu, Li Lu, Jianpeng Liu, Fengcheng Wu, Jianming Lu
In orbital Chern insulators, the chemical potential acts as a tuning knob to reverse chirality in dissipationless edge currents, enabling electric-field control of magnetic order-key for future quantum electronics. Despite the rise of orbital Chern insulators, electrically switchable quantum anomalous Hall effect (QAHE) remains rare, necessitating further investigation. Here, we demonstrate electric-field-induced reversal of orbital Chern insulators in a moire superlattice composed of rhombohedral heptalayer graphene (r-7LG) aligned with hexagonal boron nitride. At one electron per moire unit cell, two emerging Chern insulating phases - one pointing away from and the other toward graphene’s charge neutrality point in the phase diagram of carrier density (n) versus magnetic field (B) - exhibit energetic competition modulated by both n and B. This switchable QAHE chirality in r-7LG demonstrates a layer-number dependent response: similar phenomena in moire r-6LG require much higher magnetic fields and are absent in thinner rhombohedral graphene. Our findings establish moire-engineered rhombohedral graphene as a promising platform for exploring topological quantum materials with electrically controllable chiral edge modes and magnetic order.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
21pages, 12 figures
Two-Dimensional Graphene-like BeO Sheet: A Promising Deep-Ultraviolet Nonlinear Optical Materials System with Strong and Highly Tunable Second Harmonic Generation
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Linlin Liu, Congwei Xie, Abudukadi Tudi, Keith Butler, Zhihua Yang
Two-dimensional (2D) materials with large band gaps and strong and tunable second-harmonic generation (SHG) coefficients play an important role in the miniaturization of deep-ultraviolet (DUV) nonlinear optical (NLO) devices. Despite the existence of numerous experimentally synthesized 2D materials, none of them have been reported to meet DUV NLO requirements. Herein, to the first time, an experimentally available graphene-like BeO monolayer only formed by NLO-active [BeO3] unit is suggested as a promising 2D DUV NLO material due to its ultrawide band gap (6.86 eV) and a strong SHG effect ({chi}“22” ^((2))(2D) = 6.81 Å\times pm/V) based on the first-principles calculations. By applying stacking, strain, and twist engineering methods, several 2D BeO sheets have been predicted, and the flexible structural characteristics endow them with tunable NLO properties. Remarkably, the extremely stress-sensitive out-of-plane {chi}“15” ^((2))(2D) and {chi}“33” ^((2))(2D) (exceptional 30% change) and the robust in-plane {chi}“22” ^((2))(2D) against large strains can be achieved together in AC-, AAC-, AAE, and ACE-stacking BeO sheets under in-plane biaxial strain, exhibiting emergent phenomena uniquely not yet seen in other known 2D NLO materials. Our present results reveal that 2D BeO systems should be a new option for 2D DUV NLO materials.
Materials Science (cond-mat.mtrl-sci)
18 pages,5 figures
Self-Consistent Field Theory for Semiflexible Gaussian Chain Model
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Yutaka Oya, Toshihiro Kawakatsu
Self-consistent field theory (SCFT) is one of the useful methods to simulate phase separated structures of multi-component polymer systems. In this article, we propose an SCFT for semiflexible polymer melts, where the basic equations for the SCFT are derived by introducing a bending stiffness into a flexible Gaussian bead-spring model and taking its continuous limit. Our SCFT is described by a coupled modified diffusion equations for the statistical weight of the chain conformation (path integral), which is a perturbation to semiflexible chains from the flexible Gaussian chain model. Using our modified diffusion equations, we investigated the influences of the bending stiffness on the conformations of symmetric semiflexible diblock copolymer in a strongly segregated lamellar structures and on the order-disorder transition.
Soft Condensed Matter (cond-mat.soft)
Inefficiency of the orbit Hall effect on spin torque in transition metal/ferromagnet bilayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Yizhuo Song, Jialin Tian, Fanxing Zheng, Jianting Dong, Meng Zhu, Jia Zhang
Electric field or current induced spin torque is crucial for spintronic devices, for instance the spin-orbit torque MRAM (magnetic random access memory). In this work, we systematically investigate the spin torque in transition metals(TM)/ferromagnets(FM) bilayers by using first-principles calculations. In order to examine the spin and orbital Hall contribution, the studied transition metals includes heavy metal Pt, W, Au as well as light metals Ti, V, Cr, Cu etc. The ferromagnets have been chosen to be CoFe and Ni, with the former being relevant for SOT-MRAM and the latter may exhibit large orbital Hall contribution. We found that in TM/CoFe bilayers with typical 3d and 5d transition metals, the spin torque on CoFe mainly originates from spin Hall mechanism with the magnitude and sign of spin torque efficiency consistent with the spin Hall conductivity. In TM/Ni bilayers, the spin Hall effect in bulk TM and Ni itself are account for the origin of spin torque. In both systems, we do not see effective contribution from orbital Hall effect in transition metals on the spin torque in TM/FM bilayers.
Materials Science (cond-mat.mtrl-sci)
Temperature Measurement via Time Crystal Frequencies in One-Dimensional Quantum Droplets
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Saurab Das, Jagnyaseni Jogania, Jayanta Bera, Ajay Nath
We propose a method for temperature measurement by analyzing the frequency of generated time crystals in one-dimensional (1D) quantum droplets. The system consists of a binary Bose-Einstein condensate mixture confined in a driven quasi-periodic optical lattice (QOL) with repulsive cubic effective mean-field and attractive quadratic beyond-mean-field interactions. By solving the 1D extended Gross-Pitaevskii equation, we derive the exact analytical wavefunction and investigate the droplet dynamics under different driving conditions. Specifically, we examine three cases: (i) constant driving frequency with linearly increasing QOL depth, (ii) constant QOL depth with linearly varying driving frequency, and (iii) constant driving frequency with sinusoidally modulated QOL depth. Fast Fourier Transform analysis reveals harmonic density oscillations, confirming time crystal formation. Additionally, we establish a non-trivial correlation between time crystal frequency and system temperature, demonstrating that an increase in time crystal frequency leads to oscillatory variations in the magnitude of the droplet’s negative temperature. Finally, numerical stability analysis confirms that the obtained solutions remain robust, ensuring their feasibility for experimental realization.
Quantum Gases (cond-mat.quant-gas), Pattern Formation and Solitons (nlin.PS)
Extended Haldane model – a modern gateway to topological insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
The seminal Haldane model brings up a paradigm beyond the quantum Hall effect to look for a plethora of topological phases in the honeycomb and other lattices. Here we dwell into this model considering a full parameter space in the presence of spin-orbit interaction as well as Zeeman field such that the flavour of Kane-Mele model is invoked. Adopting this extended Haldane model as an example, we elucidate, in a transparent manner, a number of topological features in a pedagogical manner. First, we describe various first order topological insulator phases and their characterizations while explaining various anomalous quantum Hall effects and quantum spin Hall effects in the extended Haldane model. Second, we demonstrate the concepts of higher order topological insulator phases along with the topological invariants in the anisotropic limit of the extended Haldane model. At the end, we discuss various open issues involving \textcolor{black}{emergent or extended} symmetries that might lead to a broader understanding of various topological phases and the associated criteria behind their emergence.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
Topical Review in J. Phys.: Condens. Matter 37 153001 (2025) – Focus Issue on Topological Physics: From Fundamentals to Applications
Direct Summation of the Madelung Constant using Axial Multipoles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Joven V. Calara (1), Jan D. Miller (2) ((1) Dept of Engineering, Salt Lake Community College, Salt Lake City, Utah (2) Dept of Metallurgy, University of Utah, Salt Lake City, Utah)
A direct summation method for the Madelung constant calculation is presented where a crystal lattice is constructed from linear arrays of charges or axial multipoles. An array is designed to have vanishing low order electric moments such that its potential at the origin from a distance $r$ decays at least as fast as $r^{-5}$, but preferably as fast as $r^{-13}$. High potential decay rates render the summation absolutely convergent in up to 6 dimensions. Convergence speed increases with higher decay rates. It is also shown that the limit approached by the summation is independent of the growth geometry. Madelung constants for NaCl bulk, surface, and edge lattice points are calculated, as well as on off-lattice points such as interstitial positions and external neighborhoods of surfaces. In addition, bulk CsCl Madelung constant was calculated. In 1D, 2D, and 3D, accuracy of 13 decimal places are attained within 40 nearest neighbor distance from the reference ion.
Materials Science (cond-mat.mtrl-sci)
LLM-Fusion: A Novel Multimodal Fusion Model for Accelerated Material Discovery
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Onur Boyar, Indra Priyadarsini, Seiji Takeda, Lisa Hamada
Discovering materials with desirable properties in an efficient way remains a significant problem in materials science. Many studies have tackled this problem by using different sets of information available about the materials. Among them, multimodal approaches have been found to be promising because of their ability to combine different sources of information. However, fusion algorithms to date remain simple, lacking a mechanism to provide a rich representation of multiple modalities. This paper presents LLM-Fusion, a novel multimodal fusion model that leverages large language models (LLMs) to integrate diverse representations, such as SMILES, SELFIES, text descriptions, and molecular fingerprints, for accurate property prediction. Our approach introduces a flexible LLM-based architecture that supports multimodal input processing and enables material property prediction with higher accuracy than traditional methods. We validate our model on two datasets across five prediction tasks and demonstrate its effectiveness compared to unimodal and naive concatenation baselines.
Materials Science (cond-mat.mtrl-sci), Artificial Intelligence (cs.AI), Machine Learning (cs.LG)
4 pages, presented at AAAI 2025 Workshop on AI to Accelerating Science and Engineering (AI2ASE)
Brownian-motion approach to statistical mechanics: Langevin equations, fluctuations, and timescales
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Sushanta Dattagupta, Aritra Ghosh
We briefly review the problem of Brownian motion and describe some intriguing facets. The problem is first treated in its original form as enunciated by Einstein, Langevin, and others. Then, utilizing the problem of Brownian motion as a paradigm and upon using the Langevin equation(s), we present a brief exposition of the modern areas of stochastic thermodynamics and fluctuation theorems in a manner accessible to a non-expert. This is followed by an analysis of non-Markovian Brownian dynamics via generalized Langevin equation(s) in which we particularly shed light onto its derivation, the emergence of the fluctuation-dissipation relation, and the recently-discovered effective-mass framework.
Statistical Mechanics (cond-mat.stat-mech), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Chemical Physics (physics.chem-ph), Classical Physics (physics.class-ph)
Invited review in the special collection entitled ‘250 Years of Brownian Motion’ published by Physics of Fluids
Phys. Fluids 37, 027199 (2025)
Ruddlesden-Popper defects act as a free surface: role in formation and photophysical properties of CsPbI3
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Weilun Li, Qimu Yuan, Yinan Chen, Joshua R. S. Lilly, Marina R. Filip, Laura M. Herz, Michael B. Johnston, Joanne Etheridge
The perovskite semiconductor, CsPbI3, holds excellent promise for solar cell applications due to its suitable bandgap. However, achieving phase-stable CsPbI3 solar cells with high power conversion efficiency remains a major challenge. Ruddlesden-Popper (RP) defects have been identified in a range of perovskite semiconductors, including CsPbI3. However, there is limited understanding as to why they form or their impact on stability and photophysical properties. Here we increase the prevalence of RP defects with increased Cs-excess in vapour-deposited CsPbI3 thin films and observe superior structural stability but inferior photophysical properties. Significantly, using electron microscopy, we find that the atomic positions at the planar defect are comparable to those of a free surface, revealing their role in phase stabilisation. Density functional theory (DFT) calculations reveal the RP planes are electronically benign, however, antisites observed at RP turning points are likely to be malign. We therefore propose that increasing RP planes while reducing RP turning points could offer a breakthrough for improving both phase stability and photophysical performance. The formation mechanism revealed here may well apply more generally to RP structures in other perovskite systems.
Materials Science (cond-mat.mtrl-sci)
Optimizing GaAs/AlGaAs Growth on GaAs (111)B for Enhanced Nonlinear Efficiency in Quantum Optical Metasurfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
T. Blaikie (1), M. C. Tam (1), S. Stich (2), M. Belkin (2), Z. R. Wasilewski (1 and 3 and 4) ((1) Electrical and Computer Engineering, University of Waterloo, (2) Walter Schottky Institute Technical University of Munich, (3) Physics and Astronomy, University of Waterloo, (4) Waterloo Institute for Nanotechnology)
This study is an optimization of GaAs and Al${0.55}$Ga${0.45}$As growth on GaAs (111)B substrates with a surface misorientation of 2° towards [$\bar{2}$11], aiming to enhance surface morphology. For quantum optical metasurfaces (QOMs) the change from (001) growth to (111) growth will increase the efficiency of the nonlinear process of spontaneous parametric downconversion (SPDC). This work identifies key factors affecting surface roughness, including the detrimental effects of traditional thermal oxide desorption, which prevented growth of smooth surfaces. A novel Ga-assisted oxide desorption method using Ga flux “pulses” was developed, successfully removing oxides while preserving surface quality. In-situ characterization techniques, including reflection high energy electron diffraction (RHEED) and a novel technique called Diffuse Laser Scattering (DLS), were employed to monitor and control the oxide removal process. Mounting quarter wafers with sapphire substrates as optical diffusers improved surface uniformity by mitigating temperature gradients. The uniformity of the growths was clearly visualized by an in-house technique called black box scattering (BBS) imaging. Indium (In) was tested as a surfactant to promote step-flow growth in GaAs, which resulted in atomic-scale flatness with root mean square (RMS) roughness as low as 0.256 nm. In combination with a higher growth temperature, the RMS roughness of Al${0.55}$Ga${0.45}$As layers was reduced to 0.302 nm. The optimized growth methods achieved acceptable roughness levels for QOM fabrication, with ongoing efforts to apply these techniques to various devices based on GaAs/AlGaAs heterostructures with (111) orientation.
Materials Science (cond-mat.mtrl-sci)
9 pages, 6 figures. This paper will be submitted to Journal of Vacuum Science and Technology A
Synthesized Kuramoto potential via optomechanical Floquet engineering
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Motoki Asano, Hajime Okamoto, Hiroshi Yamaguchi
Synchronization is a ubiquitous scientific phenomenon in various physical systems. Here, we examine the feasibility of generating multistable and dynamically tunable synchronization by using the technique of Floquet engineering. Applying a periodically modulated laser light to optomechanical oscillators allows for stable and precise control of oscillator couplings. This enables us not only to explore the physics of quantized integer and fractional phase slips but also synthesize multioctave synchronizations of mechanical oscillators that exhibit tailorable multistability. Furthermore, the dynamically manipulated synchronizations lead to an exotic topology wherein the phase trajectories have a nontrivial winding number and giant non-reciprocity. This scheme could help to elucidate the dynamics of complicated oscillator networks like biological systems and to mimic their highly efficient information processing.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
Contactless measurements of the elastic modulus of living cells using thermal fluctuations of AFM cantilever
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Hao Zhang, Zaicheng Zhang, Etienne Harte, Francoise Argoul, Abdelhamid Maali
We present a contactless method for measuring the elastic modulus of living cells (human triple-negative breast cancer, MDA-MB-231) from the thermal fluctuations of an atomic force microscope (AFM) cantilever. By analyzing the power spectral density (PSD) of the cantilevers thermal fluctuations, we obtain the resonance frequencies of its first three modes at various cell to cantilever separation distances. By comparing measurements on living cells with those on a rigid borosilicate sphere of the same size, we extract the frequency shift caused by the elasto-hydrodynamic coupling between the cantilever fluctuations and the deformations of the cells. We then fit this frequency shift using an elasto-hydrodynamic model that integrates hydrodynamic forces and cell deformation. This approach allows us to determine the elastic modulus values of the living cells for the first three resonant frequencies of the cantilever.
Soft Condensed Matter (cond-mat.soft)
An interpretable continuum framework for decision-making: nonreciprocal field theory of the shepherding control problem
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Andrea Lama, Mario di Bernardo, Sabine H. L. Klapp
Field theories for complex systems traditionally focus on collective behaviors emerging from simple, reciprocal pairwise interaction rules. However, many natural and artificial systems exhibit behaviors driven by microscopic decision-making processes that introduce both nonreciprocity and many-body interactions, challenging these conventional approaches. We develop a theoretical framework to incorporate decision-making into field theories using the shepherding control problem as a paradigmatic example, where agents (herders) must coordinate to confine another group of agents (targets) within a prescribed region. By introducing continuous approximations of two key decision-making elements - target selection and trajectory planning - we derive field equations that capture the essential features of distributed control. Our theory reveals that different decision-making strategies emerge at the continuum level, from random to highly selective choices, and from undirected to goal-oriented motion, driving transitions between homogeneous and confined configurations. The resulting nonreciprocal field theory not only describes the shepherding problem but provides a general framework for incorporating decision-making into continuum theories of collective behavior, with implications for applications ranging from robotic swarms to crowd management systems.
Soft Condensed Matter (cond-mat.soft), Adaptation and Self-Organizing Systems (nlin.AO)
Probing $p$-wave effects in spin-density separation of Bose mixtures by dynamic structure factor
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Quantum mixtures of Bose gases with tunable $s$- and $p$-wave interactions offer a versatile platform to explore strongly correlated phases and exotic phenomena. While repulsive interactions often drive phase separation, the interplay of $p$-wave interactions with spin-density decoupling remains underexplored. In this work, we employ the path integal field theory to investigate the role of $p$-wave interactions in three-dimensional two-component Bose gas. We derive the Lee-Huang-Yang corrections to the ground-state energy and quantum depletion, revealing how $p$-wave interactions modify equations of state of the model system. Furthermore, we demonstrate that $p$-wave interactions predominantly renormalize the spin-sector effective mass in the language of decoupling the density and spin-density degrees of freedom. This effect manifests in the dynamic structure factor, computed via hydrodynamic theory, where Bragg spectroscopy can detect a tunable splitting between spin and density modes. Our results bridge theoretical predictions with experimental observables, offering insights into anisotropic interaction effects in quantum gases and their implications for probing emergent phases.
Quantum Gases (cond-mat.quant-gas)
11 pages, 3 figures
Interfacial strong coupling and negative dispersion of propagating polaritons in freestanding oxide membranes
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Brayden Lukaskawcez, Shivasheesh Varshney, Sooho Choo, Sang Hyun Park, Dongjea Seo, Liam Thompson, Devon Uram, Hayden Binger, Steve Koester, Sang-Hyun Oh, Tony Low, Bharat Jalan, Alexander McLeod
Membranes of complex oxides like perovskite SrTiO3 extend the multi-functional promise of oxide electronics into the nanoscale regime of two-dimensional materials. Here we demonstrate that free-standing oxide membranes supply a reconfigurable platform for nano-photonics based on propagating surface phonon polaritons. We apply infrared near-field imaging and -spectroscopy enabled by a tunable ultrafast laser to study pristine nano-thick SrTiO3 membranes prepared by hybrid molecular beam epitaxy. As predicted by coupled mode theory, we find that strong coupling of interfacial polaritons realizes symmetric and antisymmetric hybridized modes with simultaneously tunable negative and positive group velocities. By resolving reflection of these propagating modes from membrane edges, defects, and substrate structures, we quantify their dispersion with position-resolved nano-spectroscopy. Remarkably, we find polariton negative dispersion is both robust and tunable through choice of membrane dielectric environment and thickness and propose a novel design for in-plane Veselago lensing harnessing this control. Our work lays the foundation for tunable transformation optics at the nanoscale using polaritons in a wide range of freestanding complex oxide membranes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Main text: 29 pages, 5 figures. Supplementary information: 12 pages, 2 figures
Huge Stress-induced Adiabatic Temperature Change in a High-Toughness All-d-metal Heusler Alloy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Rui Cai, Zhiyang Wei, Hongjie Ren, Hanyang Qian, Xinyu Zhang, Yao Liu, Xiang Lu, Wen Sun, Meng Gao, Enke Liu, Jian Liu, Guowei Li
The elastocaloric effect (eCE), referring to the thermal effect triggered by a uniaxial stress, provides a promising and versatile routine for green and high efficient thermal management. However, current eCE materials generally suffer from relatively low eCE and poor mechanical properties, hindering their practical applications. Here, we report a exceptionally huge eCE with a directly measured adiabatic temperature change of up to 57.2 K in a dual-phase all-d-metal Heusler Mn50Ni37.5Ti12.5 polycrystalline alloy, revealing an extra contribution to the latent heat during the stress-induced martensitic transformation from B2 to L10, and breaking the record of adiabatic temperature change for elastocaloric alloys. Moreover, thanks to the combined strengthening effect of d-d hybridization and well-dispersed secondary cubic {\gamma} phase, the alloy can endure a uniaxial stress up to 1760 MPa. Such an abnormal huge eCE is attributed to the combination of the enhanced entropy change associated with a stress-induced B2 to L10 martensitic transformation under higher stress, in contrast with the thermally induced B2 to 5-layer modulated structure one, and the high transformation fraction due to the multi-point nucleation facilitated by the {\gamma} phase dispersed in the main phase. This work provides insight into making full use of the transformation heat to enhance the caloric effect for high-efficient thermal management systems.
Materials Science (cond-mat.mtrl-sci)
Do chain topology and polydispersity affect the two-stage heteropolymer coil-globule transition?
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Thoudam Vilip Singh, Lenin S. Shagolsem
The thermodynamic behavior of collapse transition in a fully flexible coarse-grained model of energy polydisperse polymer (EPP), a statistical model of random heteropolymer, is investigated in an implicit solvent by means of molecular dynamics (MD) simulations. Each monomer has interaction energy, $\varepsilon_i$, randomly drawn from a Gaussian distribution, and is characterised by polydispersity index, $\delta$ = standard deviation/mean, where the mean is fixed at $\langle \varepsilon \rangle$ = 2.5. Polymers of different chain topologies assume an expanded coil conformation at high temperature, and undergo a melting transition called a coil-globule transition when temperature is lowered. They collapse into molten globules. Further decrease in temperature results in a liquid-solid transition called a freezing transition, thus, creating crystallite structures at very low temperatures. The current study investigates the effect of chain topology and energy polydispersity in this regard from thermodynamic point of view.
Soft Condensed Matter (cond-mat.soft)
5 pages, 4 figures
Deconfined criticality as intrinsically gapless topological state in one dimension
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Sheng Yang, Fu Xu, Da-Chuan Lu, Yi-Zhuang You, Hai-Qing Lin, Xue-Jia Yu
Deconfined criticality and gapless topological states have recently attracted growing attention, as both phenomena go beyond the traditional Landau paradigm. However, the deep connection between these two critical states, particularly in lattice realization, remains insufficiently explored. In this Letter, we reveal that certain deconfined criticality can be regarded as an intrinsically gapless topological state without gapped counterparts in a one dimensional lattice model. Using a combination of field-theoretic arguments and large-scale numerical simulations, we establish the global phase diagram of the model, which features deconfined critical lines separating two distinct spontaneous symmetry breaking ordered phases. More importantly, we unambiguously demonstrate that the mixed anomaly inherent to deconfined criticality enforces topologically robust edge modes near the boundary, providing a general mechanism by which deconfined criticality manifests as a gapless topological state. Our findings not only offer a new perspective on deconfined criticality but also deepen our understanding of gapless topological phases of matter.
Strongly Correlated Electrons (cond-mat.str-el), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
4 pages with supplemental materials, 9 figures
Experimentally achieving minimal dissipation via thermodynamically optimal transport
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Shingo Oikawa, Yohei Nakayama, Sosuke Ito, Takahiro Sagawa, Shoichi Toyabe
Optimal transport theory, originally developed in the 18th century for civil engineering, has since become a powerful optimization framework across disciplines, from generative AI to cell biology. In physics, it has recently been shown to set fundamental bounds on thermodynamic dissipation in finite-time processes. This extends beyond the conventional second law, which guarantees zero dissipation only in the quasi-static limit and cannot characterize the inevitable dissipation in finite-time processes. Here, we experimentally realize thermodynamically optimal transport using optically trapped microparticles, achieving minimal dissipation within a finite time. As an application to information processing, we implement the optimal finite-time protocol for information erasure, confirming that the excess dissipation beyond the Landauer bound is exactly determined by the Wasserstein distance - a fundamental geometric quantity in optimal transport theory. Furthermore, our experiment achieves the bound governing the trade-off between speed, dissipation, and accuracy in information erasure. To enable precise control of microparticles, we develop scanning optical tweezers capable of generating arbitrary potential profiles. Our work establishes an experimental approach for optimizing stochastic thermodynamic processes. Since minimizing dissipation directly reduces energy consumption, these results provide guiding principles for designing high-speed, low-energy information processing.
Statistical Mechanics (cond-mat.stat-mech)
33 pages, 16 figures, including Methods and SI
Insight into interplay between bandstructure and Coulomb interaction via quasiparticle interference
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
Garima Goyal, Dheeraj Kumar Singh
Quasiparticle interference has been used frequently for the purpose of unraveling the electronic states in the vicinity of the Fermi level as well as the nature of superconducting gap in the unconventional superconductors. Using the metallic spin-density wave state of iron pnictides as an example, we demonstrate that the quasiparticle interference can also be used as a probe to provide crucial insight into the interplay of the electronic bandstructure and correlation effects in addition to bringing forth the essential features of electronic states in the vicinity of the Fermi level. Our study reveals that the features of quasiparticle interference pattern can help us narrowing down the interaction parameter window and choose a more realistic tight-binding model.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
10 pages, 6 figures
Pre-training Graph Neural Networks with Structural Fingerprints for Materials Discovery
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Shuyi Jia, Shitij Govil, Manav Ramprasad, Victor Fung
In recent years, pre-trained graph neural networks (GNNs) have been developed as general models which can be effectively fine-tuned for various potential downstream tasks in materials science, and have shown significant improvements in accuracy and data efficiency. The most widely used pre-training methods currently involve either supervised training to fit a general force field or self-supervised training by denoising atomic structures equilibrium. Both methods require datasets generated from quantum mechanical calculations, which quickly become intractable when scaling to larger datasets. Here we propose a novel pre-training objective which instead uses cheaply-computed structural fingerprints as targets while maintaining comparable performance across a range of different structural descriptors. Our experiments show this approach can act as a general strategy for pre-training GNNs with application towards large scale foundational models for atomistic data.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Non-trivial phonon dynamics and significant electron-phonon coupling of the high frequency modes in a Dirac semimetal
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Debasmita Swain, Akash Dey, Anushree Roy, Kush Saha, Sitikantha D. Das
Using finite temperature Raman spectroscopy, we investigate the electron-phonon interactions
(EPI) and phonon-phonon scattering dynamics in the Dirac semimetal Cd3As2 in different fre quency regimes. Strong softening of the Raman shifts below 200 K is observed for almost all the
phonon modes with a marked deviation from the standard anharmonic behavior. The experimen tally observed Raman linewidth seems to be captured well by a combination of EPI, relevant at
low temperature (LT) and phonon-phonon scattering, which is predominant at high temperatures
(HT), leading to an observable minima in the thermal evolution of the linewidth. While this fea ture is most prominently observed in the highest-frequency Raman mode (196 cm-1), its intensity
gradually diminishes as the Raman frequency decreases. Computation of the electronic contribution
to the phonon linewidth, for both the high and low frequency modes, from the phonon self-energy
shows that it qualitatively mimics the experimental observations. It is found that phonon-induced
interband scattering results in the presence of a maxima in phonon linewidth that crucially depends
on the finiteness of the chemical potential.
Strongly Correlated Electrons (cond-mat.str-el)
Phys. Rev. B 111, 035143 (2025)
Effects of the three-dimensional interplanar coupling on the centrosymmetric skyrmion crystal formation in the frustrated stacked-triangular Heisenberg model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
R. Osamura, K. Aoyama, K. Mitsumoto, H. Kawamura
Effects of the three-dimensional (3D) interplanar coupling on centrosymmetric skyrmion crystal (SkX) formation is investigated via extensive Monte Carlo simulations on the frustrated isotropic Heisenberg model on a stacked-triangular lattice in both cases of the ferromagnetic (F) and the antiferromagnetic (AF) nearest-neighbor interplanar coupling $J_{1c}$. The SkX phase is stabilized at finite fields and at finite temperatures for both F and AF $J_{1c}$, although it is destabilized by modestly weak AF $J_{1c}$. The magnetic phase diagram of the 3D short-range model is more or less similar to those of the 2D short-range model and of the 2D long-range RKKY model. We find that an intriguing phenomenon of replica-symmetry breaking, popular in glass physics and recently identified in the SkX phase of the 3D long-range RKKY model [K. Mitsumoto and H. Kawamura, Phys. Rev. B {\bf 104}, 184432 (2021)], does not arise in the 3D short-range model, suggesting that the long-range nature of interaction might be necessary to realize the RSB in centrosymmetric SkX state.
Strongly Correlated Electrons (cond-mat.str-el)
Magnon damping and mode softening in quantum double-exchange ferromagnets without Jahn-Teller phonons
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
A. Moreo, E. Dagotto, G. Alvarez, T. Tohyama, M. Mierzejewski, J. Herbrych
We present a comprehensive analysis of the magnetic excitations and electronic properties of fully quantum double-exchange ferromagnets, i.e., systems where ferromagnetic ordering emerges from the competition between spin, charge, and orbital degrees of freedom, but without the canonical approximation of using classical localized spins. Specifically, we investigate spin excitations within the Kondo lattice-like model, as well as a two-orbital Hubbard Hamiltonian in proximity to the orbital-selective Mott phase. Computational analysis of the magnon dispersion, damping, and spectral weight within these models reveals unexpected phenomena, such as magnon mode softening and the anomalous decoherence of magnetic excitations as observed in earlier experimental efforts, but explained here without the use of the phononic degrees of freedom. We show that these effects are intrinsically linked to incoherent spectral features near the Fermi level, which arise due to the quantum nature of the local (on-site) triplets. This incoherent spectrum leads to a Stoner-like continuum on which spin excitations scatter, governing magnon lifetime and strongly influencing the dynamical spin structure factor. Our study explores the transition from coherent to incoherent magnon spectra by varying the electron density. Furthermore, we demonstrate that the magnitude of the localized spin mitigates decoherence by suppressing the incoherent spectral contributions near the Fermi level. We also discuss the effective $J_1$-$J_2$ spin Hamiltonian, which can accurately describe the large doping region characterized by the magnon-mode softening. Finally, we show that this behavior is also present in multiorbital models with partially filled orbitals, namely, in systems without localized spin moments, provided that the model is in a strong coupling regime.
Strongly Correlated Electrons (cond-mat.str-el)
Predicting the Néel temperatures in general helimagnetic materials: a comparison between mean field theory, random phase approximation, renormalized spin wave theory and classical Monte Carlo simulations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Varun Rajeev Pavizhakumari, Thomas Olsen
The critical temperature for magnetic order comprises a crucial property of any magnetic material and ranges from a few Kelvin in certain antiferromagnets to 1400 K in ferromagnetic Co. However, the prediction of critical temperatures based on, for example, a spin wave dispersion is in general non-trivial. For ferromagnets and simple collinear antiferromagnets, estimates may be obtained from the Heisenberg model using either renormalized spin wave theory or the Green’s function random phase approximation (RPA), but a systematic assessment of the accuracy of such approaches seems to be lacking in the literature. In this work, we propose generalizations of both renormalized spin wave theory and RPA to calculate the critical temperatures of single-$Q$ helimagnetic ground states, which include ferromagnets and antiferromagnets as special cases. We compare the methods to classical Monte Carlo simulations and Mean field theory, using experimental exchange parameters for a wide range of materials; MnO and NiO (single site Néel ground states), MnF$_2$ (altermagnet), Cr$_2$O$_3$ and Fe$_2$O$_3$ (two site Néel states) and Ba$_3$NbFe$_3$Si$2$O${14}$ (incommensurate helimagnet). In all cases, we observe that predictions from RPA are in excellent agreement with experimental values and RPA thus constitutes a rather reliable all-purpose method for calculating critical temperatures.
Materials Science (cond-mat.mtrl-sci)
17 pages, 8 figures
Encounter-based model of a run-and-tumble particle with stochastic resetting
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
In this paper we analyze the effects of stochastic resetting on an encounter-based model of an unbiased run-and-tumble particle (RTP) confined to the half-line $[0,\infty)$ with a partially absorbing wall at $x=0$. The RTP tumbles at a constant rate $\alpha$ between the velocity states $\pm v$ with $v>0$. Absorption occurs when the number of collisions with the wall (discrete local time) exceeds a randomly generated threshold $\widehat{\ell}$ with probability distribution $\Psi(\ell)$. The extended RTP model has three state variables, namely, particle position $X(t)\in [0,\infty)$, the velocity direction $\sigma(t)\in{-1, 1}$, and the discrete local time $L(t)\in {\mathbb N}$. We initially assume that only $X(t)$ and $\sigma(t)$ reset at a Poisson rate $r$, whereas $L(t)$ is not changed. This implies that resetting is not governed by a renewal process. We use the stochastic calculus of jump processes to derive an evolution equation for the joint probability distribution of the triplet $(X(t),\sigma(t),L(t))$. This is then used to calculate the mean first passage time (MFPT) by performing a discrete Laplace transform of the evolution equation with respect to the local time. We thus find that the MFPT’s only dependence on the distribution $\Psi$ is via the mean local time threshold. We also identify parameter regimes in which the MFPT is a unimodal function of both the resetting and tumbling rates. Finally, we consider conditions under which resetting is given by a renewal process and show how the MFPT in the presence of local time resetting depends on the full statistics of $\Psi$.
Statistical Mechanics (cond-mat.stat-mech), Quantitative Methods (q-bio.QM)
28 pages, 8 figures
Diffusion-mediated adsorption versus absorption at partially reactive targets: a renewal approach
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Renewal theory is finding increasing applications in non-equilibrium statistical physics. One example relates the probability density and survival probability of a Brownian particle or an active run-and-tumble particle with stochastic resetting to the corresponding quantities without resetting. A second example is so-called snapping out Brownian motion, which sews together diffusions on either side of an impermeable interface to obtain the corresponding stochastic dynamics across a semi-permeable interface. A third example relates diffusion-mediated surface adsorption-desorption (reversible adsorption) to the case of irreversible adsorption. In this paper we apply renewal theory to diffusion-mediated adsorption processes in which an adsorbed particle may be permanently removed (absorbed) prior to desorption. We construct a pair of renewal equations that relate the probability density and first passage time (FPT) density for absorption to the corresponding quantities for irreversible adsorption. We first consider the example of diffusion in a finite interval with a partially reactive target at one end. We use the renewal equations together with an encounter-based formalism to explore the effects of non-Markovian adsorption/desorption on the moments and long-time behaviour of the FPT density for absorption. We then analyse the corresponding renewal equations for a partially reactive semi-infinite trap and show how the solutions can be expressed in terms of a Neumann series expansion. Finally, we construct higher-dimensional versions of the renewal equations and derive general expression for the FPT density using spectral decompositions.
Statistical Mechanics (cond-mat.stat-mech)
42 pages, 12 figures
An exact formula for the contraction factor of a subdivided Gaussian topological polymer
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Jason Cantarella, Tetsuo Deguchi, Clayton Shonkwiler, Erica Uehara
We consider the radius of gyration of a Gaussian topological polymer $G$ formed by subdividing a graph $G’$ of arbitrary topology (for instance, branched or multicyclic). We give a new exact formula for the expected radius of gyration and contraction factor of $G$ in terms of the number of subdivisions of each edge of $G’$ and a new weighted Kirchhoff index for $G’$. The formula explains and extends previous results for the contraction factor and Kirchhoff index of subdivided graphs.
Statistical Mechanics (cond-mat.stat-mech), Combinatorics (math.CO)
Coexistence of topological surface states and superconductivity in Dirac semimetal NiTe$_2$
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
Chen He, Jian-Zhou Zhao, Mei Du, Luo-Zhao Zhang, Jia-Ying Zhang, Kuo Yang, Noah F. Q. Yuan, Aleksandr Seliverstov, Ewald Janssens, Jun-Yi Ge, Zhe Li
The coexistence of topological bands around the Fermi level ($E_F$) and superconductivity provides a fundamental platform for exploring their interplay. However, few materials inherently display both properties. In this study, we demonstrate the coexistence of topological surface states at the $E_F$ and superconductivity in NiTe$_2$ single crystals, a material hitherto not recognized as superconducting. Quasiparticle interference measurements performed via scanning tunneling microscopy suggest the presence of topological surface states at the $E_F$, which is further corroborated by density functional theory simulations. Experimental evidence for superconductivity is provided via electronic transport measurements and specific heat capacity analyses. Our results suggest that NiTe$_2$ represents a promising platform for investigating the rich interplay between topological states and superconductivity.
Superconductivity (cond-mat.supr-con)
Ultrafast dynamics of carriers, coherent acoustic phonons and strain pulses in BiSbTe1.5Se1.5 topological insulator thin films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Anupama Chauhan, Sidhanta Sahu, Poulami Ghosh, Dheerendra Singh, Sambhu G Nath, Anjan Kumar N M, P.K. Panigrahi, Chiranjib Mitra, N. Kamaraju
We Investigate the ultrafast carrier, coherent acoustic phonons (CAPs), and acoustic strain pulse dynamics in topological insulator BiSbTe1.5Se1.5 (BSTS) thin films of varying thickness using degenerate pump-probe reflection spectroscopy. Here, Sapphire has been chosen as the main substrate due to its maximum acoustic reflectivity at the BSTS-sapphire interface compared to BSTS-GaAs, BSTS-Si, and BSTS-MgO interfaces. For the films with thickness more than twice the penetration depth, the transient reflectivity data predominantly exhibits travelling acoustic strain pulses (TASP) on the top of single-exponential electronic decay (~ 2 ps). In contrast, films with thickness less than penetration depth are dominated by CAPs and a bi exponential electronic background with decay times of ~ 2 ps and ~ 260-380 ps. The observed TASP dynamics are well-described by a theoretical acoustic strain model. Further, to elucidate the underlying physical mechanisms governing the behavior of photo-excited carriers, CAPs, and strain pulses, we performed carrier density and temperature-dependent (7-294 K) studies on BSTS films with thicknesses of 22 nm and 192 nm. In the 22 nm film, the both fast and slow decay processes increase with carrier density at room temperature but decrease with temperature at a carrier density of 1.7\ast10^{19} cm^{-3}. A detailed analysis suggests that the faster decay arises from electron-phonon scattering and carrier diffusion, while the slower decay likely results from defect-assisted and phonon-assisted recombination. Furthermore, increasing the sample temperature leads to anharmonic decay induced softening of ~ 14 % in the phonon frequency and an anomalous ~ 48 % decrease in the phonon damping parameter due to reduced Dirac surface electron and acoustic phonon scattering.
Materials Science (cond-mat.mtrl-sci)
40 pages, 18 Figures
Haldane Fractional Statistics for 1D Heisenberg Spin XXX Chain
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Wei-Jia Liu, Jia-Jia Luo, Xi-Wen Guan
Haldane’s fractional exclusion statistics (FES) describes a generalized Pauli exclusion statistics, which can be regarded as an emergent quantum statistics induced by the intrinsic dynamical interaction. A non-mutual FES has been identified at the quantum criticality of the one-dimensional (1D) and 2D interacting Bose Gas [Nat. Sci. Rev. 9, nwac027 (2022)]. It is naturally asked if such a non-mutual FES can be induced by the spin-spin interaction in the antiferromagnetic spin-1/2 XXX chain? In this article, we first represent the Bethe ansatz equations of spin strings in terms of the FES equations of different species. Then we show that the 1D spin XXX chain remarkably possesses the non-mutual FES in the critical region. We observe that the equation of state in terms of the FES gives rises to full statistical properties of the model at quantum criticality, which are in good agreement with the results obtained from the thermodynamic Bethe ansatz (TBA) equations of the model. From the non-mutual FES, we also precisely determine the quantum scaling functions, which further agree well with the previous TBA results [Phys. Rev. B 96, 220401(R) (2017)]. Finally, we also build up an exact mapping between the scaling functions of the Lieb-Liniger model and the spin Heisenberg spin chain at quantum criticality. Our method provides deep insights into the critical phase of matter from quantum FES point of view.
Strongly Correlated Electrons (cond-mat.str-el)
12 pages, 7 figures
Modulating Optical Properties through Cation Substitution: Composition-Property Relationships in $M^I_3$$M^{III}$P$_3$O$_9$N:Eu$^{2+}$ ($M^I$=Na, K; $M^{III}$=Al, Ga, In)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Nakyung Lee, Justyna Zeler, Małgorzata Sójka, Eugeniusz Zych, Jakoah Brgoch
Developing phosphors with narrow photoluminescence emission peaks and high chromatic stability holds significant importance in light-emitting diode (LED) display technologies, where a wide color gamut is essential to achieve the Rec. 2020 specifications. This research focuses on the optical properties of a solid solution: $M^I_{2.97}$Eu${0.015}$M^{III}$P$3$O$9$N [$M^I$=Na, K; $M^{III}$=Al, (Al${0.75}$Ga${0.25}$), (Al${0.5}$Ga${0.5}$), (Al${0.25}$Ga${0.75}$), Ga, (Ga${0.75}$In${0.25}$), (Ga${0.5}$In$_{0.5}$)] to understand how the narrow-emitting photoluminescence in K$_3$AlP$3$O$9$N:Eu$^{2+}$ can evolve during host structure cation substitution. Photoluminescence measurements at low temperature (15 K) support that Eu$^{2+}$ replaces three crystallographically independent Na$^+$ sites in Na${2.97}$Eu${0.015}$AlP$3$O$9$N, similar to the parent K$^+$ phosphor, but substituting Ga$^{3+}$ and In$^{3+}$ for Al$^{3+}$ leads to a change in Eu$^{2+}$ site preference, narrowing the full-width-at-half-maximum (fwhm) of the emission peak. The chromatic stability and photoluminescence quantum yield are also enhanced with higher Ga$^{3+}$ content in the host but not with In$^{3+}$. Thermoluminescence analysis indicates the relationship between trap states and the enhanced quantum yield with Ga$^{3+}$ leads to the series’ best performance. The analysis of the $M^I{2.97}$Eu${0.015}$M^{III}$P$_3$O$_9$N series offers insight into the potential method for modulating optical properties with cation substitution in the host structure.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Statistical physics analysis of graph neural networks: Approaching optimality in the contextual stochastic block model
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-04 20:00 EST
Graph neural networks (GNNs) are designed to process data associated with graphs. They are finding an increasing range of applications; however, as with other modern machine learning techniques, their theoretical understanding is limited. GNNs can encounter difficulties in gathering information from nodes that are far apart by iterated aggregation steps. This situation is partly caused by so-called oversmoothing; and overcoming it is one of the practically motivated challenges. We consider the situation where information is aggregated by multiple steps of convolution, leading to graph convolutional networks (GCNs). We analyze the generalization performance of a basic GCN, trained for node classification on data generated by the contextual stochastic block model. We predict its asymptotic performance by deriving the free energy of the problem, using the replica method, in the high-dimensional limit. Calling depth the number of convolutional steps, we show the importance of going to large depth to approach the Bayes-optimality. We detail how the architecture of the GCN has to scale with the depth to avoid oversmoothing. The resulting large depth limit can be close to the Bayes-optimality and leads to a continuous GCN. Technically, we tackle this continuous limit via an approach that resembles dynamical mean-field theory (DMFT) with constraints at the initial and final times. An expansion around large regularization allows us to solve the corresponding equations for the performance of the deep GCN. This promising tool may contribute to the analysis of further deep neural networks.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG)
Quasiparticle picture of topological phase transitions induced by interactions
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
S. S. Krishtopenko, A. V. Ikonnikov, F. Hartmann, S. Höfling, B. Jouault, F. Teppe
We present a general recipe to describe topological phase transitions in condensed matter systems with interactions. We show that topological invariants in the presence of interactions can be efficiently calculated by means of a non-Hermitian quasiparticle Hamiltonian introduced on the basis of the Green’s function. As an example analytically illustrating the application of the quasiparticle concept, we consider a topological phase transition induced by the short-range electrostatic disorder in a two dimensional system described by the Bernevig-Hughes-Zhang model. The latter allows us to explicitly demonstrate the change in the $\mathbb{Z}_2$ topological invariant and explain the quantized values of the longitudinal conductance in a certain range of the Fermi energy and the disorder strength found previously in numerical calculations.
Materials Science (cond-mat.mtrl-sci)
12 pages, 3 figures
Conductance, continuity, and ferromagnetic percolation thresholds in thin films
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Gregory Kopnov, Alexander Gerber
Classical percolation models predict the metal-insulator transition and the onset of the long-range ferromagnetic order at the same topological continuity threshold. We tested this prediction in thin films of ferromagnetic CoPd and found a dramatic difference between the conductance and magnetic thresholds. While the long-range ferromagnetic phase develops at or very close to the continuity threshold, the transition from the metal-like to insulator-like conductance develops in films several times thinner. We argue that atomically narrow low resistance gaps intersecting the fractal network of metallic clusters provide a consistent explanation of the effect. We identify the conduction threshold as the point in discontinuous films at which the resistance of intergranular junctions exceeds the quantum resistance mark.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 figures
Efficient shortcuts-to-adiabaticity for loading an ultracold Fermi gas into higher orbital bands of one-dimensional optical lattice
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Hang Yu, Haoyi Zhang, Bolong Jiao, Qinxuan Peng, Liao Sun, Jiaming Li, Le Luo
We propose an experimental scheme to load ultracold Fermi gases from the ground orbital band of a one-dimensional optical lattice into the first excited orbital band. Unlike the narrow momentum distribution of a Bose-Einstein Condensate, Fermi gases exhibit a broad momentum distribution. To address this, we define the average loading efficiency across all quasi-momentum states and theoretically perform the loading operation simultaneously for each Bloch state. Using a multiparameter global optimization method, we determine the loading efficiency at various lattice depths. We can enhance the loading efficiency by adjusting the phase of the lattice, which leverages the different symmetries of Bloch wavefunctions in various optical lattice orbitals. We also identified that the primary factor hindering higher loading efficiency in the Fermi gas is the multiple occupancy of the quasi-momentum states. Our simulations of various occupancies revealed a decreasing trend in mean loading efficiency as the number of occupied quasi-momentum states increases. Finally, we compare our method with other loading techniques and assess its experimental feasibility.
Quantum Gases (cond-mat.quant-gas)
9 pages, 8 figures
Temporal Correlations and Inelastic Dynamics in a Vibrated Binary Granular Mixture
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Rameez Farooq Shah, Syed Rashid Ahmad, Shikha Kumari
We investigate the dynamics of binary mixtures of inelastic particles through event-driven molecular dynamics simulations, focusing on velocity autocorrelation functions (VACFs). The study examines two distinct particle types under varying inelasticity conditions, systematically analyzing coefficients of restitution (CoR) ranging from 0.80 to 0.95. Like-particle interactions (AA and BB) maintain equal CoR values, while unlike-particle interactions (AB) are assigned the average CoR. The simulation framework incorporates a vibrating base system to maintain energy input and system stability. Our analysis reveals significant differences in VACF decay rates between Type 1 and Type 2 particles, demonstrating non-equipartition of energy within the binary mixture. The degree of this disparity is strongly influenced by the coefficient of restitution, with lower CoR values leading to more pronounced differences between particle types. These findings provide insights into the complex dynamics of granular gases and the role of inelasticity in energy distribution within binary mixtures. Our study contributes to the understanding of non-equilibrium statistical mechanics in granular systems and has potential implications for industrial processes involving particulate materials, such as fluidized beds and pneumatic conveying systems.
Soft Condensed Matter (cond-mat.soft), Computation (stat.CO)
Beyond Born-Oppenheimer Green’s function theories: absolute and relational
New Submission | Other Condensed Matter (cond-mat.other) | 2025-03-04 20:00 EST
We consider quantum field theoretic many-body Green’s function approach to solve the Coulomb many-body problem. The earlier beyond Born-Oppenheimer Green’s function theories are absolute in nature and are based on the non-reduced Hamiltonian. Motivated by the issues following this approach we have developed a reduced Green’s function theory which is relational in nature. The central differences between these approaches trace back to the relational-absolute debate, which has continued for over two thousand years since the time of Aristotle and still persists today. We highlight that these aspects of the theories are connected to several areas of modern physics, including relational quantum mechanics, quantum reference frames, superselection rules, the separation of different types of motion and spontaneous symmetry breaking. The starting point of any such exact theory must be absolute, given that the global conservation laws hold. However, for the observables to be meaningful, they must be defined with respect to the relative space. Approximations, such as the one introduced by Born and Oppenheimer, can break global symmetries and make certain parts of the absolute description well-defined. We highlight that spontaneous symmetry breaking is not necessary to explain the existence of solids, but entities such as phonons can be naturally explained within the relational theory.
Other Condensed Matter (cond-mat.other), Quantum Physics (quant-ph)
11 pages. Submitted to the proceedings of DICE2024, to appear in Journal of Physics: Conference Series
The emergent dynamics of double-folded randomly branching ring polymers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Elham Ghobadpour, Max Kolb, Ivan Junier, Ralf Everaers
The statistics of randomly branching double-folded ring polymers are relevant to the secondary structure of RNA, the large-scale branching of plectonemic DNA (and thus bacterial chromosomes), the conformations of single-ring polymers migrating through an array of obstacles, as well as to the conformational statistics of eukaryotic chromosomes and melts of crumpled, non-concatenated ring polymers. Double-folded rings fall into different dynamical universality classes depending on whether the random tree-like graphs underlying the double-folding are quenched or annealed, and whether the trees can undergo unhindered Brownian motion in their spatial embedding. Locally, one can distinguish (i) repton-like mass transport around a fixed tree, (ii) the spontaneous creation and deletion of side branches, and (iii) displacements of tree node, where complementary ring segments diffuse together in space. Here we employ dynamic Monte Carlo simulations of a suitable elastic lattice polymer model of double-folded, randomly branching ring polymers to explore the mesoscopic dynamics that emerge from different combinations of the above local modes in three different systems: ideal non-interacting rings, self-avoiding rings, and rings in the melt state. We observe the expected scaling regimes for ring reptation, the dynamics of double-folded rings in an array of obstacles, and Rouse-like tree dynamics as limiting cases. Of particular interest, the monomer mean-square displacements of $g_1\sim t^{0.4}$ observed for crumpled rings with $\nu=1/3$ are similar to the subdiffusive regime observed in bacterial chromosomes. In our analysis, we focus on the question to which extent contributions of different local dynamical modes to the emergent dynamics are simply additive. Notably, we reveal a non-trivial acceleration of the dynamics of interacting rings, when all three types of local motion are present.
Soft Condensed Matter (cond-mat.soft), Computational Physics (physics.comp-ph)
Leap into the future: shortcut to dynamics for quantum mixtures
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Pablo Capuzzi, Zehra Akdeniz, Patrizia Vignolo
The study of the long-time dynamics of quantum systems can be a real challenge, especially in systems like ultracold gases, where the required timescales may be longer than the lifetime of the system itself. In this work, we show that it is possible to access the long-time dynamics of a strongly repulsive atomic gas mixture in shorter times. The shortcut-to-dynamics protocol that we propose does not modify the fate of the observables, but effectively jumps ahead in time without changing the system’s inherent evolution. Just like the fast-forward button in a movie player that allows to quickly reach the part of the movie one wants to watch, it is a leap into the future.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
5 pages, 4 figures
Tail-induced equilibration in long-range interacting quantum lattices
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
We examine the relation between inter-particle interactions and real-time equilibration in one-dimensional lattice systems with hard-core constraints. Focusing on the roles of interactions, our results demonstrate that in the presence of interaction tails, any power-law exponent (including the limit ones) can encode the random particle configurations to the Hamiltonian, leaving the latter characterized by random matrices. Through an experimental-accessible setup using dipolar-interacting particles in optical lattices, the quenched relaxations are demonstrated resulting in equilibrium, and the relation between eigenstate thermalization is confirmed. Our study directly unveiled the role of inter-particle interactions in quantum many-body dynamics, offering a new scheme to address equilibration in closed quantum many-body problem based on the manifesting of random particle configurations in the model Hamiltonian.
Quantum Gases (cond-mat.quant-gas)
Confinement-induced unatomic trimer states in mass-imbalanced systems
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Rafael M. Francisco, D. S. Rosa, T. Frederico, M. T. Yamashita, G. Krein
As resonantly interacting trimers of the type AAB are progressively squeezed from $D=3$ to $D=2$, unatomic states emerge. We calculated the contacts from the high momentum tail of the single particle densities. The sharp increase of the contacts serves as a signature of the transition between the Efimov and unatomic regimes, characterized by the emergence of continuous scale invariance when the system reaches a critical dimension, $D_c$. This continuous scale invariance starts to dominate the behavior of the system at the dimension $\overline{D}<D_c$, below which the trimers momentum distribution tails exhibit a power-law behavior signaling the unatomic regime. To illustrate our findings, we studied compounds of the forms $^{7}$Li$-^{23}$Na${2}$, $^{7}$Li$-^{87}$Rb${2}$ and $^{7}$Li$-^{133}$Cs$_{2}$. The increase in the mass-imbalance of the trimers reduces the interval between $D_c$ and $\overline{D}$. The emergence of unatomic states can be experimentally verified by observing the two-body contact parameter, which is a quantity directly related to the thermodynamic properties of the gas.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
Dynamical exponents as an emergent property at interacting topological quantum critical points
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Fan Yang, Zheng-Cheng Gu, Fei Zhou
In standard studies of quantum critical points (QCPs), the dynamical exponent $z$ is introduced as a fundamental parameter along with global symmetries to identify universality classes. Often, the dynamical exponent $z$ is set to be one as the most natural choice for quantum field theory representations, which further implies emergence of higher space-time symmetries near QCPs in many condensed matter systems. In this article, we study a family of topological quantum critical points (tQCPs) where the $z=1$ quantum field theory is prohibited in a fundamental representation by a protecting symmetry, resulting in tQCPs with $z=2$. We further illustrate that when strong interactions are properly taken into account, the stable weakly interacting gapless tQCPs with $z=2$ can further make a transition to another family of gapless tQCPs with dynamical exponent $z=1$, without breaking the protecting symmetry. Our studies suggest that dynamical exponents, as well as the degrees of freedom in fermion fields, can crucially depend on interactions in topological quantum phase transitions; in tQCPs, to a large extent, they are better thought of as emergent properties.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 2 figures
Universal whirling magnetic orders in non-Heisenberg Tsai-type quasicrystal approximants
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Farid Labib, Kazuhiro Nawa, Yusuke Nambu, Hiroyuki Takakura, Yoichi Ikeda, Kazuhiko Deguchi, Masato Matsuura, Asuka Ishikawa, Ryoichi Kajimoto, Kazuhiko Ikeuchi, Taku J. Sato, Ryuji Tamura
Magnetic orders of non-Heisenberg Tsai-type 1/1 approximant crystals (ACs) in the Au-Ga-Dy system were studied through bulk magnetization, neutron diffraction, and inelastic neutron scattering techniques. The results uncovered noncoplanar, ferromagnetic (FM) and antiferromagnetic (AFM) spin configurations whirling along [111] crystallographic axis, which is analogous to those observed in the Tb- and Ho-contained counterparts. The crystal electric field excitations similar to those in the Tb-based counterpart are also observed indicating the strong Ising-like magnetic anisotropy. These comprehensive experiments and analyses have revealed the existence of a universal mechanism that stabilizes noncoplanar FM and AFM structures in non-Heisenberg Tsai-type ACs, independent of the rare-earth species (Tb, Dy, Ho); FM intra-cluster interactions and strong Ising-like anisotropy.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Quantum Physics (quant-ph)
9 pages, 12 figures
A multi-component phase-field model for T1 precipitates in Al-Cu-Li alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Ali Reza Safi, Elizabeth Mathew, Rupesh Chafle, Benjamin Klusemann
In this study, the role of elastic and interfacial energies in the shape evolution of T1 precipitates in Al-Cu-Li alloys is investigated using phase-field modeling. We employ a formulation considering the stoichiometric nature of the precipitate phase explicitly, including coupled equation systems for various order parameters. Inputs such as elastic properties are derived from DFT calculations, while chemical potentials are obtained from CALPHAD databases. This methodology provides a framework that is consistent with the derived chemical potentials to study the interplay of thermodynamic, kinetic, and elastic effects on T1 precipitate evolution in Al-Cu-Li alloys. It is shown that diffusion-controlled lengthening and interface-controlled thickening are important mechanisms to describe the growth of T1 precipitates. Furthermore, the study illustrates that the precipitate shape is significantly influenced by the anisotropy in interfacial energy and linear reaction rate, however, elastic effects only play a minor role.
Materials Science (cond-mat.mtrl-sci)
“Half-Bogoliubons” as the intermediate states for the phase coherence in underdoped cuprates
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
Han Li, Zhaohui Wang, Shengtai Fan, Jiaseng Xu, Huan Yang, Hai-Hu Wen
Superconductivity is achieved by the pairing of electrons and phase coherence between the Cooper pairs. According to the Bardeen-Cooper-Schrieffer theory, the quasiparticles with Bogoliubov dispersion exists and reveal particle-hole symmetric coherence peaks on the single particle tunneling spectrum. Here we report the observation of two kinds of tunneling spectra showing only one side of the “coherence peak” but with symmetric energies (about +-11 meV) in underdoped cuprate superconductor Bi2Sr2-xLaxCuO6 single crystals (p=0.114) with fractional superconductivity. Merging these two kinds of spectra can mimic the complete Bogoliubov dispersion, thus we name the electronic states associated with these half-peaked spectrum as “half Bogoliubons”. In previous studies, it was shown that two doped holes may bind into a local pair within the 4a0 x 4a0 plaquette of CuO bonds (a0: distance between nearest Cu atoms). We attribute the “half-Bogoliubons” to the intermediate states for the phase coherence, and they correspond to the three-hole and one-hole states as the excited ones from the local pairing state of two holes. An entanglement of these two “half-Bogoliubons” would mean the dynamic hopping of charge freedom resulting in the phase coherence between the local paired states. Our results unravel a unique process for establishing the phase coherence through exchanging a charge between the regions with local pairs.
Superconductivity (cond-mat.supr-con)
32 pages, 8 figures (Including main text and Supplementary Materials)
Tracking Cluster Continuity and Dynamics in Time-Series Data: Application to Chromatin Polymer Simulations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
This study presents an enhanced method for analyzing cluster dynamics, with a particular focus on tracking clusters’ continuity over time using time-series data from molecular dynamics (MD) simulation. The proposed method was applied to spatio-temporal cluster data obtained from a non-equilibrium MD simulation of a chromatin polymer model. In this model, clusters are formed on the polymer by binding molecules that stochastically and temporarily bind to the polymer segments at finite rates. Our analysis successfully tracked the dynamics of clusters, including merging and splitting events, and revealed that clusters exhibit a percolation transition in both spatial and temporal domains. This suggests that clusters in the chromatin polymer model can persist even under finite rates of attractive interactions, demonstrating that the method can capture complex cluster dynamics over time.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)
6 pages, 4 figures
Giant non-reciprocal band structure effect in a multiferroic material
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Srdjan Stavrić, Giuseppe Cuono, Baishun Yang, Álvaro R. Puente-Uriona, Julen Ibañez-Azpiroz, Paolo Barone, Andrea Droghetti, Silvia Picozzi
Multiferroic materials, characterized by the coexistence of ferroelectricity and ferromagnetism, may unveil band structures suggestive of complex phenomena and new functionalities. In this Letter, we analyze the band structure of EuO in its multiferroic phase. Using density functional theory calculations and detailed symmetry analysis, we reveal a previously overlooked non-reciprocal band structure effect, where the electronic energy bands exhibit asymmetry along opposite directions with respect to the special points in the Brillouin zone. This effect, which is enabled by spin-orbit coupling, is giant for the top valence Eu $4f$ bands, and can be switched by external electric or magnetic fields. Furthermore, this results in an enhanced bulk photovoltaic effect. Specifically, our predictions indicate the emergence of a large injection current response to linearly polarized light, resulting in a photoconductivity value several orders of magnitude higher than that reported in any other oxide material. Ultimately, this non-reciprocal band structure effect and the associated large bulk photovoltaic response may be general phenomena emerging not just in EuO but also in other multiferroics or magnetoelectrics, potentially providing new cross-functionalities.
Materials Science (cond-mat.mtrl-sci)
6 pages, 3 figures, 8 supplementary pages, 10 supplementary figures
Flat bands and temperature-driven phase transition in quasi-one-dimensional zigzag chains
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
Jisong Gao, Haijun Cao, Xuegao Hu, Hui Zhou, Zhihao Cai, Qiaoxiao Zhao, Dong Li, Zhicheng Gao, Shin-ichiro Ideta, Kenya Shimada, Peng Cheng, Lan Chen, Kehui Wu, Sheng Meng, Baojie Feng
Flat-band materials have garnered extensive attention due to their captivating properties associated with strong correlation effects. While flat bands have been discovered in several types of 2D materials, their existence in 1D systems remains elusive. Here, we propose a 1D frustrated lattice, specifically the 1D zigzag lattice, as a platform for hosting flat bands. This lattice can be experimentally realized by growing CuTe chains on Cu(111). The presence of flat bands was confirmed by tight-binding model analysis, first-principles calculations, and angle-resolved photoemission spectroscopy measurements. In addition, we discovered a temperature-driven phase transition at approximately 250 K. Detailed analyses demonstrate that the system has a Tomonaga-Luttinger liquid behavior, accompanied by spin-charge separation effects. Our work unveils new prospects for investigating strongly correlated electron behaviors and topological properties in the 1D limit.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Physical Review Letters 134, 086202 (2025)
Self-interacting processes via Doob conditioning
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-04 20:00 EST
Francesco Coghi, Juan P. Garrahan
We connect self-interacting processes, that is, stochastic processes where transitions depend on the time spent by a trajectory in each configuration, to Doob conditioning. In this way we demonstrate that Markov processes with constrained occupation measures are realised optimally by self-interacting dynamics. We use a tensor network framework to guide our derivations. We illustrate our general results with new perspectives on well-known examples of self-interacting processes, such as random walk bridges, excursions, and forced excursions.
Statistical Mechanics (cond-mat.stat-mech)
12 pages + References, 4 figures
First-principles Hubbard parameters with automated and reproducible workflows
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Lorenzo Bastonero, Cristiano Malica, Eric Macke, Marnik Bercx, Sebastian P. Huber, Iurii Timrov, Nicola Marzari
We introduce an automated, flexible framework (aiida-hubbard) to self-consistently calculate Hubbard $U$ and $V$ parameters from first-principles. By leveraging density-functional perturbation theory, the computation of the Hubbard parameters is efficiently parallelized using multiple concurrent and inexpensive primitive cell calculations. Furthermore, the intersite $V$ parameters are defined on-the-fly during the iterative procedure to account for atomic relaxations and diverse coordination environments. We demonstrate the scalability and reliability of the framework by computing in high-throughput fashion the self-consistent onsite $U$ and intersite $V$ parameters for 115 Li-containing bulk solids. Our analysis of the Hubbard parameters calculated reveals a significant correlation of the onsite $U$ values on the oxidation state and coordination environment of the atom on which the Hubbard manifold is centered, while intersite $V$ values exhibit a general decay with increasing interatomic distance. We find, e.g., that the numerical values of $U$ for Fe and Mn 3d orbitals can vary up to 3 eV and 6 eV, respectively; their distribution is characterized by typical shifts of about 0.5 eV and 1.0 eV upon change in oxidation state, or local coordination environment. For the intersite $V$ a narrower spread is found, with values ranging between 0.2 eV and 1.6 eV when considering transition metal and oxygen interactions. This framework paves the way for the exploration of redox materials chemistry and high-throughput screening of $d$ and $f$ compounds across diverse research areas, including the discovery and design of novel energy storage materials, as well as other technologically-relevant applications.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
Is Triboelectricity Confusing, Confused or Complex?
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Karl P. Olson, Laurence D. Marks
In this report, we look at the fundamental physics of triboelectricity, charge transfer due to contact and sliding. While much of the report focuses upon recent advances such as the incorporation of flexoelectric contributions, we also include older work, some from centuries ago, which only now can be understood in a general sense. Basic concepts and theories ranging from elements of tribology and contact mechanics through semiconductor built-in potentials, electromechanical terms, mechanochemistry and trap states are briefly described, linking to established surface science and interface physics. We then overview the main models that have been proposed, showing that they all fall within conventional electrostatics combined with other established science. We conclude with some suggestions for the future. Based upon this overview, our conclusion is that triboelectricity is a slightly complex combination of standard electrostatic phenomena that can be understood using the generalized Ampere’s law connecting the electric displacement field with both Coulomb and polarization contributions, and the free carrier density, that is Grad.D=rho. Triboelectricity may be confusing, it is not really confused if care is taken, but it is complex.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Soft Condensed Matter (cond-mat.soft)
Submitted review with 93 pages, 30 Figures and 552 references
Nonuniform superconducting states caused by odd-frequency Cooper pairs
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-04 20:00 EST
Takumi Sato, Satoru Hayami, Shingo Kobayashi, Yasuhiro Asano
We discuss the origin of a nonuniform superconducting state in which Cooper pairs have a finite center of mass momentum. The instability to such a nonuniform superconducting state is analyzed by a pole of the pair fluctuation propagator for weak coupling superconductors. The results show that odd(even)-frequency Cooper pairs stabilize a nonuniform (uniform) superconducting phase below the transition temperature. We provide a theoretical framework that explains the reasons for appearing the nonuniform superconducting states.
Superconductivity (cond-mat.supr-con)
Exchange-phase erasure in anyonic Hong-Ou-Mandel interferometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Sushanth Varada, Christian Spånslätt, Matteo Acciai
Two-particle interferometry is an important tool for extracting the exchange statistics of quantum particles. We theoretically investigate the prospects of such interferometry to probe the statistics of point-like anyonic excitations injected in a Hong-Ou-Mandel (HOM) setup based on a quantum point contact device in the fractional quantum Hall regime. We compute the standard HOM ratio, i.e., the ratio of tunneling noises for two- and one-particle injections, and find that for point-like anyons, it only depends on the temperature and the anyon scaling dimension. Importantly, the latter is not necessarily related to the exchange phase. In fact, we establish that the HOM ratio does not reveal the exchange phase of the injected anyons: For injection-time delays that are small compared to the thermal time scale, we find that the exchange phase accumulated due to time-domain braiding between injected and thermally activated anyons is erased due to two mutually canceling sub-processes. In contrast, for time delays large compared to the thermal time, only a single sub-process contributes to the braiding, but the accumulated phase is canceled in the HOM ratio. These findings suggest caution when interpreting HOM interferometry experiments with anyons and approaches beyond the standard HOM ratio are thus necessary to extract anyonic statistics with two-particle interferometry experiments.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
6 + 4 pages, 4 figures, to be submitted to Phys. Rev. B
Hydrogen bond-driven interactions between chitosan and biobased surfactants: A study of bulk behavior and surface adsorption
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-04 20:00 EST
Ana Puente-Santamaria, Josselyn N. Molina-Basurto, Eva Gerardin, Francisco Ortega, Ramon G. Rubio, Eduardo Guzman
This study explores the hydrogen bond-mediated association between chitosan (CHI) and alkyl polyglucoside (APG), a bio-based surfactant, in acidic conditions with varying ionic strengths. Unlike conventional polyelectrolyte-surfactant interactions that depend on electrostatic forces, the association in this system relies purely on non-ionic interactions. Using UV visible spectroscopy, phase diagrams, and quartz crystal microbalance with dissipation monitoring (QCM-D), the bulk phase behavior and adsorption characteristics of CHI-APG mixtures on negatively charged surfaces was studied. Results demonstrate that APG concentration controls the phase behavior, with moderate levels inducing coacervate formation, while higher ionic strengths promote this coacervation through enhanced hydrogen bonding interactions. This shift leads to the formation of a phase separated morphology, with micronsized coacervate droplets observable in solution. Zeta potential measurements suggest that these droplets adopt a core shell structure, characterized by a hydrophobic core due to the surfactant s alkyl chains and a hydrophilic shell formed by chitosan. Additionally, the coacervation process significantly enhances the adsorption of CHI APG complexes onto solid substrates, a feature with potential applications in targeted delivery and controlled release systems. Overall, this study provides critical insights into the design of bio-based, sustainable formulations and expands the understanding of hydrogen bond-driven, nonelectrostatic coacervation, relevant for applications in cosmetics, biomedical coatings, and environmentally friendly materials.
Soft Condensed Matter (cond-mat.soft)
Published in Journal of Molecular Liquids 425 (2025) 127259
Journal of Molecular Liquids 425 (2025) 127259
Doping-Driven Modulation of Spin-Orbit Coupling, Spin Textures, and Rashba-Edelstein Response in Chiral Tellurium: A First-Principles Study
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Chiral semiconductors such as elemental tellurium (Te) exhibit unconventional spin textures and
large charge-to-spin conversion efficiencies, yet the influence of doping on these properties remains
underexplored. Here, we address this gap by investigating how substituting Te with lighter (S,
Se) or heavier (Sb) elements systematically modifies the spin-orbit-driven phenomena in chiral Te,
including the band structure, spin Berry curvature, and Rashba-Edelstein response. The objective is
to determine whether doping strategies can be leveraged to optimize collinear spin textures, enhance
spin accumulation, and possibly extend spin lifetimes-all crucial aspects for magnet-free spintronics.
Using density functional theory calculations implemented in Quantum ESPRESSO, combined with
tight-binding interpolation in PAOFLOW, we map out the doping-dependent electronic states and
quantify their associated spin transport coefficients. Our findings reveal that lighter dopants shift
the Fermi level to regions of pronounced spin splitting, thereby increasing the magnitude of spin current conversion, whereas heavier dopants can introduce or remove near-degenerate bands that
strongly affect spin-orbit coupling. In both scenarios, the fundamental chirality of Te remains
robust, preserving the radial or “collinear” spin-momentum locking. These results not only confirm
that doping is a potent and feasible route for tuning spin-orbit phenomena but also offer practical
guidelines for experimental efforts aiming to engineer chiral semiconductors for spin devices. By
correlating dopant identity with specific spin-texture enhancements, this study paves the way for
rationally designing next-generation spintronic components free from external magnetic fields.
Materials Science (cond-mat.mtrl-sci)
Mesoscopic scale study of lateral dynamics of Sn-intercalation of the buffer layer on SiC
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Benno Harling, Zamin Mamiyev, Christoph Tegenkamp, Martin Wenderoth
The dynamics of Sn intercalation of the buffer layer on SiC was investigated with a frozen-in diffusion front using Kelvin Probe Force Microscopy. The technique allows to laterally distinguish between intercalated regions and the pristine buffer layer. Comparing topography features with the surface potential on the mesoscopic scale confirms that surface steps act as transport barriers. The results show a distinct pin hole mechanism for the material flow from terrace to terrace of the vicinal substrate surface. Nucleation and the formation of tin intercalated phase on terraces happen at steps. This results in a mesoscopic growth against the macroscopic diffusion direction.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
13 pages main text with 5 figures and 5 pages supplemental information with 4 figures. Keywords: Epitaxial Graphene, Intercalation, AFM/KPFM, SiC, Sn Tin, Diffusion
Dynamics of single Au nanoparticles on graphene simultaneously in real- and diffraction space by time-series convergent beam electron diffraction
New Submission | Other Condensed Matter (cond-mat.other) | 2025-03-04 20:00 EST
Sara Mustafi, Rongsheng Cai, Sam Sullivan-Allsop, Matthew Smith, Nicholas J. Clark, Matthew Lindley, Ding Peng, Kostya S. Novoselov, Sarah J. Haigh, Tatiana Latychevskaia
Convergent beam electron diffraction (CBED) on two-dimensional materials allows simultaneous recording of the real-space image (tens of nanometers in size) and diffraction pattern of the same sample in one single-shot intensity measurement. In this study, we employ time-series CBED to visualize single Au nanoparticles deposited on graphene. The real-space image of the probed region, with the amount, size, and positions of single Au nanoparticles, is directly observed in the zero-order CBED disk, while the atomic arrangement of the Au nanoparticles is available from the intensity distributions in the higher-order CBED disks. From the time-series CBED patterns, the movement of a single Au nanoparticle with rotation up to 4° was recorded. We also observed facet diffraction lines - intense bright lines formed between the CBED disks of the Au nanoparticle, which we explain by diffraction at the Au nanoparticle’s facets. This work showcases CBED as a useful technique for studying adsorbates on graphene using Au nanoparticles as a model platform, and paves the way for future studies of different objects deposited on graphene.
Other Condensed Matter (cond-mat.other), Computational Physics (physics.comp-ph), Optics (physics.optics)
Investigation of O interstitial diffusion in $β$-Ga$_2$O$_3$: direct approach via master diffusion equations
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Grace McKnight, Channyung Lee, Elif Ertekin
Monoclinic $\beta$-Ga$2$O$3$, a promising wide band gap semiconducting material, exhibits complex, anisotropic diffusional characteristics and mass transport behavior as a results of its low symmetry crystal structure. From first-principles calculations combined with master diffusion equations, we determine three-dimensional diffusion tensors for neutral ($\text{O}{\text{i}}^{0}$) and 2- charged oxygen interstitials ($\text{O}{\text{i}}^{2-}$). Systematic exploration of the configurational space identifies stable configurations in these two dominant charge states and their corresponding formation energies. By connecting every pair of low-energy configurations considering both interstitial or interstitialcy hops, we construct three-dimensional diffusion networks and evaluate hopping barriers of all transition pathways in networks. Combining the collection of (i) defect configurations and their formation energies and (ii) the hopping barriers that link them, we construct and solve the master diffusion equations for $\text{O}{\text{i}}^{0}$ and $\text{O}{\text{i}}^{2-}$ separately through the Onsager approach, resulting in respective three-dimensional diffusion tensors D${\text{O}{\text{i}}}^{0}$ and D${\text{O}{\text{i}}}^{2-}$. Both $\text{O}{\text{i}}^{0}$ and $\text{O}{\text{i}}^{2-}$ present the fastest diffusion along the $b$-axis, demonstrating significant anisotropy. The predicted self-diffusivities along [100] and [$\overline{2}01$] align well with previously reported values from isotopically labeled oxygen tracer experiments, highlighting the reliability of the approach in capturing complex diffusion mechanisms.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Computational Physics (physics.comp-ph)
7 figures, 5 supplemental figures
Growth dynamics of graphene buffer layer formation on ultra-smooth SiC(0001) surfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Julia Guse, Stefan Wundrack, Marius Eckert, Peter Richter, Susanne Wolff, Niclas Tilgner, Philip Schädlich, Markus Gruschwitz, Kathrin Küster, Benno Harling, Martin Wenderoth, Christoph Tegenkamp, Thomas Seyller, Rainer Stosch, Klaus Pierz, Hans Werner Schumacher, Teresa Tschirner
In this study the growth process of epitaxial graphene on SiC was investigated systematically. The transition from the initial buffer layer growth to the formation of the first monolayer graphene domains was investigated by various techniques: atomic force microscopy, low energy electron diffraction, low energy electron microscopy, Raman spectroscopy, scanning tunneling spectroscopy and scanning electron microscopy. The data show that the buffer layer formation goes along with a simultaneous SiC decomposition which takes place as a rapid step retraction of one specific type of SiC bilayer in good agreement with the step retraction model. Once the buffer layer coverage is completed, the resulting characteristic regular repeating terrace and step height pattern of one and two SiC bilayers turned out to be very stable against further SiC decomposition. The following initial growth of monolayer graphene domains occurs, interestingly, only along the two bilayer high terrace edges. This behavior is explained by a preferential SiC decomposition at the higher step edges and it has some potential for spatial graphene growth control. The corresponding earlier graphene growth on one terrace type can explain the different scanning tunneling spectroscopy nanoscale resistivities on these terraces.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
9 pages, 5 figures
Kelvin waves in nonequilibrium universal dynamics of relativistic scalar field theories
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Viktoria Noel, Thomas Gasenzer, Kirill Boguslavski
We investigate the different degrees of freedom underlying far-from-equilibrium scaling behaviour in a relativistic, single-component $\mathrm{O}(1)$ scalar field theory in two and three spatial dimensions. In such a strongly correlated many-body system, identifying the respective roles of nonlinear wave excitations and defect dynamics is a prerequisite for understanding the universal character of time evolution far from equilibrium and thus the different possible universality classes of nonthermal fixed points. Using unequal-time two-point correlation functions, we extract information about the dominant infrared excitations and study their connections to the turbulent dynamics of topological defects created in the system. In three dimensions, the primary excitations are identified as kelvon quasiparticles, which are quantised Kelvin waves propagating along vortex lines, while in two dimensions, vortices are point defects, and the infrared dynamics is dominated by bound-state like excitations similar to Kelvin waves. In both cases, the kelvon excitations are found to be characterised by distinct time-evolving dispersion relations, subject to the coarsening dynamics close to the respective nonthermal fixed point and, thus, to the decay of superfluid turbulence in the system. Our results underline the role of topological defects and their influence on the universal dynamics of strongly correlated systems near nonthermal fixed points, complementing the analysis of large-$N$ models in $\mathrm{O}(N)$ systems.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), High Energy Physics - Phenomenology (hep-ph)
The Coherent Forward Scattering peak: a probe of non-ergodicity and symmetries in a quantum chaotic system
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
F. Arrouas, J. Hébraud, N. Ombredane, E. Flament, D. Ronco, N. Dupont, G. Lemarié, B. Georgeot, Ch. Miniatura, J. Billy, B. Peaudecerf, D. Guéry-Odelin
The Coherent Backscattering (CBS) peak is a well-known interferential signature of weak localization in disordered or chaotic systems. Recently, it was realized that another interferential peak, the Coherent Forward Scattering (CFS) peak, emerges in the presence of strong localization. This peak has never been observed directly to date. We report the first direct observation of the CFS peak and demonstrate its dual role as signature of non-ergodicity and as probe of symmetries in quantum chaotic systems. Using a shaken rotor model realized with a Bose-Einstein condensate (BEC) of ultracold atoms in a modulated optical lattice, we investigate dynamical localization in momentum space. The CFS peak emerges in the position distribution as a consequence of non-ergodic dynamics, while its growth timescale depends critically on the localization scale. By finely tuning the modulation, we control the symmetries of the dynamics (time-reversal and parity) and measure their impact on both CFS and CBS peaks. Our results highlight the strong link of CFS and its temporal growth with symmetry and localization properties, establishing CFS as a robust quantitative marker of non-ergodicity. This work opens new avenues for characterizing non-ergodicity and symmetries in quantum chaotic or disordered systems, with possible applications in many-body localization and many-body chaos.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
15 pages, 12 figures
Negative exchange interaction in Si quantum dot arrays via valley-phase induced $\mathbb{Z}_2$ gauge field
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
The exchange interaction $J$ offers a powerful tool for quantum computation based on semiconductor spin qubits. However, the exchange interaction in two-electron systems in the absence of a magnetic field is usually constrained to be non-negative $J \geq 0$, which inhibits the construction of various dynamically corrected exchange-based gates. In this work, we show that negative exchange $J < 0$ can be realized in two-electron Si quantum dot arrays in the absence of a magnetic field due to the presence of the valley degree of freedom. Here, valley phase differences between dots produce a non-trivial $\mathbb{Z}_2$ gauge field in the low-energy effective theory, which in turn can lead to a negative exchange interaction. In addition, we show that this $\mathbb{Z}_2$ gauge field can break Nagaoka ferromagnetism and be engineered by altering the occupancy of the dot array. Therefore, our work uncovers new tools for exchange-based quantum computing and a novel setting for studying quantum magnetism.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
11 pages (7 main, 4 appendices) and 7 figures
A projected complex Langevin sampling method for bosons in the canonical and microcanonical ensembles
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-04 20:00 EST
Ethan C. McGarrigle, Hector D. Ceniceros, Glenn H. Fredrickson
We introduce a projected complex Langevin (CL) numerical sampling method – a fictitious Langevin dynamics scheme that uses numerical projection to sample a constrained stationary distribution with highly oscillatory character. Despite the complex-valued degrees of freedom and associated sign-problem, the projected CL method succeeds as a natural extension of real-valued projected Langevin processes. In the new proposed method, complex-valued Lagrange multipliers are determined to enforce constraints to machine precision at each iteration. To illustrate the efficacy of this approach, we adapt the projected CL method to sample coherent state quantum field theories describing interacting Bose gases, which are realized in modern cold-atom experiments. We apply projected CL to two scenarios with holomorphic constraints, the canonical and microcanonical ensembles, and show that projected CL reproduces the correct thermodynamic observables. We further observe improved numerical stability and accuracy at larger timesteps when compared to the previous state-of-the-art method for performing constrained CL sampling.
Quantum Gases (cond-mat.quant-gas), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
18 pages, 4 figures
Physical Review E, 110, (2024) 065308
Intrinsic exciton transport and recombination in single-crystal lead bromide perovskite
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-04 20:00 EST
Zhixuan Bi, Yunfei Bai, Ying Shi, Tao Sun, Heng Wu, Haochen Zhang, Yubin Wang, Miao-Ling Lin, Yaxian Wang, Ping-Heng Tan, Sheng Meng, Qihua Xiong, Luyi Yang
Photogenerated carrier transport and recombination in metal halide perovskites are critical to device performance. Despite considerable efforts, sample quality issues and measurement techniques have limited the access to their intrinsic physics. Here, by utilizing high-purity CsPbBr3 single crystals and contact-free transient grating spectroscopy, we directly monitor exciton diffusive transport from 26 to 300 K. As the temperature (T) increases, the carrier mobility ({\mu}) decreases rapidly below 100 K wtih a {\mu}T^{-3.0} scaling, and then follows a more gradual {\mu}T^{-1.7} trend at higher temperatures. First-principles calculations perfectly reproduce this experimental trend and reveal that optical phonon scattering governs carrier mobility shifts over the entire temperature range, with a single longitudinal optical mode dominating room-temperature transport. Time-resolved photoluminescence further identifies a substantial increase in exciton radiative lifetime with temperature, attributed to increased exciton population in momentum-dark states caused by phonon scattering. Our findings unambiguously resolve previous theory-experiment discrepancies, providing benchmarks for future optoelectronic design.
Materials Science (cond-mat.mtrl-sci)
$\mathbb{Z}_2$-gauging and self-dualities of the $XX$ model and its cousins
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-04 20:00 EST
In this work, we investigate the one-dimensional $XX$ lattice model and its cousins through the lens of momentum and winding $U(1)$ symmetries. We distinguish two closely related $\mathbb{Z}_2$ symmetries based on their relation to the $U(1)$ symmetries, and establish a web of $\mathbb{Z}_2$-gauging relations among these models, rooted in two fundamental seeds: the $ XY \pm YX$ models. These two seeds, each self-dual under gauging of the respective $\mathbb{Z}_2$-symmetries, possess manifestly symmetric conserved charges, making transparent the connection between the noninvertible symmetries and the Kramers-Wannier duality. By leveraging the self-dualities of these two seed models, we derive the self-dualities of their cousins, including the $XX$ model and the Levin-Gu model, through appropriate gauging procedures. Moreover, under these gauging schemes, the lattice T-duality matrices take the form of the identity matrix. Finally, we unify the mapping structures of local conserved charges across these models, providing a comprehensive framework for understanding their symmetries and dualities.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th), Quantum Physics (quant-ph)
6+5 pages, 2+4 figures
Impact of charge transfer excitons on unidirectional exciton transport in lateral TMD heterostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-04 20:00 EST
Roberto Rosati, Sai Shradha, Julian Picker, Andrey Turchanin, Bernhard Urbaszek, Ermin Malic
Lateral heterostructures built of monolayers of transition metal dichalcogenides (TMDs) are characterized by a thin 1D interface exhibiting a large energy offset. Recently, the formation of spatially separated charge-transfer (CT) excitons at the interface has been demonstrated. The technologically important exciton propagation across the interface and the impact of CT excitons has remained in the dark so far. In this work, we microscopically investigate the spatiotemporal exciton dynamics in the exemplary hBN-encapsulated WSe$_2$-MoSe$_2$ lateral heterostructure and reveal a highly interesting interplay of energy offset-driven unidirectional exciton drift across the interface and efficient capture into energetically lower CT excitons at the interface. This interplay triggers a counterintuitive thermal control of exciton transport with a less efficient propagation at lower temperatures - opposite to the behavior in conventional semiconductors. We predict clear signatures of this intriguing exciton propagation both in far- and near-field photoluminescence experiments. Our results present an important step toward a microscopic understanding of the technologically relevant unidirectional exciton transport in lateral heterostructures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures; Supplementary Information