CMP Journal 2025-04-28
Statistics
Nature Materials: 4
Nature Physics: 1
arXiv: 53
Nature Materials
Ab initio structure solutions from nanocrystalline powder diffraction data via diffusion models
Original Paper | Atomistic models | 2025-04-27 20:00 EDT
Gabe Guo, Tristan Luca Saidi, Maxwell W. Terban, Michele Valsecchi, Simon J. L. Billinge, Hod Lipson
A major challenge in materials science is the determination of the structure of nanometre-sized objects. Here we present an approach that uses a generative machine learning model based on diffusion processes that are trained on 45,229 known structures. The model factors measured the diffraction pattern as well as the relevant statistical priors on the unit cell of atomic cluster structures. Conditioned only on the chemical formula and the information-scarce finite-sized broadened powder diffraction pattern, we find that our model, PXRDnet, can successfully solve the simulated nanocrystals as small as 10 Å across 200 materials of varying symmetries and complexities, including structures from all seven crystal systems. We show that our model can successfully and verifiably determine structural candidates four out of five times, with an average error among these candidates being only 7% (as measured by the post-Rietveld refinement R-factor). Furthermore, PXRDnet is capable of solving structures from noisy diffraction patterns gathered in real-world experiments. We suggest that data-driven approaches, bootstrapped from theoretical simulation, will ultimately provide a path towards determining the structure of previously unsolved nanomaterials.
Atomistic models, Computational methods, Structural properties
Bio-inspired artificial mechanoreceptors with built-in synaptic functions for intelligent tactile skin
Original Paper | Electronic devices | 2025-04-27 20:00 EDT
Seok Ju Hong, Yu Rim Lee, Atanu Bag, Hyo Soo Kim, Tran Quang Trung, M. Junaid Sultan, Dong-Bin Moon, Nae-Eung Lee
Tactile perception involves the preprocessing of signals from slowly adapting and fast-adapting afferent neurons, which exhibit synapse-like interactions between mechanoreceptors and their dendrites or terminals, transmitting signals to the brain. Emulating these adaptation and sensory memory functions is crucial for artificial tactile sensing systems. Here, inspired by human tactile afferent systems, we present an array of artificial synaptic mechanoreceptors with built-in synaptic functions by vertically integrating synaptic transistors with a reduced graphene oxide channel, an ionogel gate dielectric and an elastomeric fingerprint-like receptive layer in an all-in-one platform. Triboelectric-capacitive gating between the receptive layer and gate dielectric in response to tactile stimulation governs excitatory post-synaptic current patterns, enabling slowly adapting and fast-adapting characteristics for signal preprocessing. The artificial synaptic mechanoreceptor array demonstrated handwriting style, surface pattern and texture discrimination via machine learning using fused slowly adapting and fast-adapting post-synaptic values, offering high data efficiency and potential for intelligent skin.
Electronic devices, Information storage, Sensors and biosensors
Warm metalworking for plastic manufacturing in brittle semiconductors
Original Paper | Design, synthesis and processing | 2025-04-27 20:00 EDT
Zhiqiang Gao, Shiqi Yang, Yupeng Ma, Tian-Ran Wei, Xiaohui Chen, Wenwen Zheng, Pengfei Qiu, Xiaoqin Zeng, Lidong Chen, Xun Shi
Semiconductors are the core of modern electronics1. Because of their brittleness, semiconductors are usually processed by the complicated techniques of sputtering or deposition2,3,4, instead of the effective and versatile metalworking methods like rolling, extrusion and pressing used with metals5. Here we show that brittle semiconductors can be plastically manufactured with an extensibility as large as ~3,000% using warm metalworking, that is, plastic manufacturing at slightly elevated temperatures (empirically below 500 K). Many bulk brittle semiconductors, such as Cu2Se, Ag2Se and Bi90Sb10, can be processed like metals below 400-500 K into free-standing, large and high-quality films with a thickness from the macro-scale to the micrometre scale. A model based on temperature-dependent collective atomic displacement and thermal vibration is proposed to explain the superior plasticity. The warm-metalworked films can retain the excellent and tunable physical properties of the bulk versions, such as a high carrier mobility up to ~5,000 cm2 V-1 s-1 and tunable electrical conductivities over six orders of magnitude by adjusting the chemical composition. A case study in film thermoelectric devices demonstrates ultra-high normalized output power densities of 43-54 μW cm-2 K-2. This work suggests that brittle semiconductors can be manufactured by warm metalworking for applications in various electronics.
Design, synthesis and processing, Mechanical properties, Thermoelectrics
Intermolecular-force-driven anisotropy breaks the thermoelectric trade-off in n-type conjugated polymers
Original Paper | Electronic materials | 2025-04-27 20:00 EDT
Diego Rosas Villalva, Dennis Derewjanko, Yongcao Zhang, Ye Liu, Andrew Bates, Anirudh Sharma, Jianhua Han, Martí Gibert-Roca, Osnat Zapata Arteaga, Soyeong Jang, Stefania Moro, Giovanni Costantini, Xiaodan Gu, Martijn Kemerink, Derya Baran
Controlling the molecular orientation of conjugated polymers is a vital yet complex process to modulate their optoelectronic properties along with boosting device performance. Here we propose a molecular-force-driven anisotropy strategy to modulate the molecular orientation of conjugated polymers. This strategy relies on the intermolecular interactions, gauged by the Hansen solubility parameters framework, to provide solvent selection criteria for conjugated polymers that render films with a preferential orientation. We showcase molecular-force-driven anisotropy to overcome the inverse coupling between the electrical conductivity and Seebeck coefficient in solution-processed organic thermoelectrics, a major challenge in the field. Our kinetic Monte Carlo simulations suggest that edge-on orientations break the trade-off by increasing the in-plane delocalization length. The molecular-force-driven anisotropy approach yields a power factor of 115 μW m-1 K-2 and a figure of merit of 0.17 at room temperature for the doped n-type 2DPP-2CNTVT:N-DMBI system. This power factor is 20 times larger than that of conventional doping approaches.
Electronic materials, Thermoelectrics
Nature Physics
Storage-ring laser spectroscopy of accelerator-produced hydrogen-like 208Bi82+
Original Paper | Atomic and molecular interactions with photons | 2025-04-27 20:00 EDT
Max Horst, Zoran Andelkovic, Carsten Brandau, Rui Jiu Chen, David Freire Fernández, Christopher Geppert, Jan Glorius, Volker Hannen, Regina Heß, Phillip Imgram, Sebastian Klammes, Kristian König, Guy Leckenby, Sergey Litvinov, Yury A. Litvinov, Bernd Lorentz, Johann Meisner, Konstantin Mohr, Patrick Müller, Stephan Passon, Tim Ratajczyk, Simon Rausch, Jon Roßbach, Rodolfo Sánchez, Shahab Sanjari, Ragandeep Singh Sidhu, Uwe Spillmann, Markus Steck, Thomas Stöhlker, Ken Ueberholz, Christian Weinheimer, Danyal Winters, Wilfried Nörtershäuser
Quantum electrodynamics has been tested to accuracies below the parts-per-trillion level in light-mass systems. However, tests in heavy-mass systems with a large nuclear charge have not yet reached similar accuracy. Here we report the hyperfine-structure splitting in the 1s ground state of radioactive hydrogen-like 208Bi82+. We produced the isotope in a nuclear reaction and injected the beam into a storage ring to perform laser spectroscopy on samples of 105 ions of Bi82+ that have only a single remaining electron, which experiences extreme magnetic-field strengths. Our result for the hyperfine splitting is in excellent agreement with the most accurate prediction based on a combination of quantum electrodynamics calculations with an empirical treatment of the hyperfine-structure anomaly ratio extracted from laser spectroscopy on neutral atoms of 209Bi and 208Bi. This achievement paves the way for the most stringent test of quantum electrodynamics in strong magnetic fields and demonstrates the feasibility of laser spectroscopy on other exotic ions with low production yields.
Atomic and molecular interactions with photons, Electronic structure of atoms and molecules, Experimental nuclear physics
arXiv
Eta-pairing state in flatband lattice: Interband coupling effect on entanglement entropy logarithm
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
Seik Pak, Hanbyul Kim, Chan Bin Bark, Sang-Jin Sin, Jae-yoon Choi, Moon Jip Park
The eta-pairing state is the eigenstate of the hypercubic Hubbard model, which exhibits anomalous logarithmic scaling of entanglement entropy. In multi-band systems, eta-pairing can be exact eigenstate when the band is flat without interband coupling. However, typical flatband systems such as Lieb and Kagome lattices often feature band touchings, where interband coupling effects are non-negligible. Using the Creutz ladder, we investigate the deformation of eta-pairing states under the interband coupling effect. Our results show corrections to entanglement entropy scaling, with modified eta-pairing states displaying broadened doublons, nonuniform energy spacing, and deviations from exact behavior for configurations with more than one eta-pair, even in the large band gap limit, except at t = 0. Through a Schrieffer-Wolff transformation, we quantify corrections to the spectrum generating algebra, offering insights into the interplay between interaction-driven phenomena and band structure effects. These findings illuminate the robustness and limitations of eta-pairing in realistic flatband systems.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
9 pages, 4 figures
Anisotropic spin-blockade leakage current in a Ge hole double quantum dot
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Zhanning Wang, S. D. Liles, Joe Hillier, A. R. Hamilton, Dimitrie Culcer
Group IV quantum dot hole spin systems, exhibiting strong spin-orbit coupling, provide platforms for various qubit architectures. The rapid advancement of solid-state technologies has significantly improved qubit quality, including the time scales characterizing electrical operation, relaxation, and dephasing. At this stage of development, understanding the relations between the underlying spin-orbit coupling and experimental parameters, such as quantum dot geometry and external electric and magnetic fields, has become a priority. Here we focus on a Ge hole double quantum dot in the Pauli spin blockade regime and present a complete analysis of the leakage current under an out-of-plane magnetic field. By considering a model of anisotropic in-plane confinement and $ k^3$ -Rashba spin-orbit coupling, we determine the behaviour of the leakage current as a function of detuning, magnetic field magnitude, interdot distance, and individual dot ellipticities. We identify regions in which the leakage current can be suppressed by quantum dot geometry designs. Most importantly, by rotating one of the quantum dots, we observe that the quantum dot shape induces a strongly anisotropic leakage current. These findings provide guidelines for probing the spin-orbit coupling, enhancing the signal-to-noise ratio, and improving the precision of Pauli spin blockade readout in hole qubit architectures.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
19 pages, 10 figures
Evidence of electronic states driving current-induced insulator-to-metal transition
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
V. K. Bhartiya, R. Hartmann, F. Forte, F. Gabriele, T. Kim, G. Cuono, C. Autieri, S. Fan, K. Kisslinger, F. Camino, M. Lettieri, R. Fittipaldi, C. Mazzoli, D. N. Basov, J. Pelliciari, A. Di Bernardo, A. Vecchione, M. Cuoco, V. Bisogni
On demand current-driven insulator-to-metal transition (IMT) is pivotal for the next generation of energy-efficient and scalable microelectronics. IMT is a key phenomenon observed in various quantum materials, and it is enabled by the complex interplay of spin, lattice, charge, and orbital degrees of freedom (DOF). Despite significant prior work, the underlying mechanism of the current-driven IMT remains elusive, primarily due to the difficulty in simultaneously obtaining bulk fingerprints of all the electronic DOF. Here, we employ in-operando resonant inelastic x-ray scattering (RIXS) on Ca$ _2$ RuO$ _4$ , a prototypical strongly correlated material, to track the evolution of the electronic DOF encoded in the RIXS spectra during the current-driven IMT. Upon entering the conductive state, we observe an energy-selective suppression of the RIXS intensity, proportional to the current. Using complementary RIXS cross-section calculations, we demonstrate that the non-equilibrium conductive state emerges from the formation of correlated electronic states with a persistent Mott gap.
Strongly Correlated Electrons (cond-mat.str-el)
21 pages, 4 figures
Ferroelastic Domain Induced Electronic Modulation in Halide Perovskites
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Ganesh Narasimha, Maryam Bari, Benjamin J Lawrie, Ilia N Ivanov, Marti Checa, Sumner B. Harris, Zuo-Guang Ye, Rama Vasudevan, Yongtao Liu
Lead halide perovskites have emerged as promising materials for optoelectronic applications due to their exceptional properties. In the all-inorganic CsPbBr3 perovskites, ferroelastic domains formed during phase transitions enhance bulk transport and emissive efficiency. However, the microscopic mechanisms governing carrier dynamics remain poorly understood. In this study, we employ cathodoluminescence (CL) and micro-Raman spectroscopy to image and investigate the electronic properties of the ferroelastic domain walls in CsPbBr3 single crystals. CL measurements reveal a reduced emissive yield and a slight redshift in emission at the domain walls. Further, micro-Raman studies provide spatially resolved mapping of vibrational modes, exhibiting second-order phonon modes localized at the domain boundaries. Our findings suggest that electron-phonon coupling at twin domain walls plays a critical role in facilitating efficient charge separation, thereby improving the optoelectronic performance of the CsPbBr3 perovskites.
Materials Science (cond-mat.mtrl-sci)
25 pages, 7 figures
Eliashberg theory prediction of critical currents in superconducting thin films under DC electric fields
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-28 20:00 EDT
Giovanni Alberto Ummarino, Alessio Zaccone, Alessandro Braggio, Francesco Giazotto
Superconducting thin metallic films, functioning as supercurrent gate-tunable transistors, have considerable potential for future quantum electronic devices. Despite extensive research, a comprehensive microscopic quantitative mechanism that elucidates the control or suppression of supercurrents in thin films remains elusive. Focusing on NbN, a prototypical material, and starting from a phenomenological ansatz that links the critical electric field with the kinetic energy parameter needed to break Cooper pairs, we provide a quantitative analysis of the critical current using Eliashberg theory in the dirty limit without adjustable parameters. The critical kinetic energy value is identified, corresponding to the maximum supercurrent that can flow in the thin film. The peak in supercurrent density as a function of the Cooper pairs’ kinetic energy arises from the interplay between the increase in supercurrent due to increased kinetic energy and the depairing effect when the kinetic energy becomes sufficiently large. The critical value of the pair’s kinetic energy is subsequently employed to estimate the critical value of an external electric field required to suppress superconductivity in the sample. This estimation is in parameter-free agreement with the experimental observations. Although the disorder reduces the temperature dependence of the gating effect on the critical current, at the same time, it increases the unscreened critical electric field needed to suppress superconductivity. This enables the proposal of methods to control and reduce the critical field value necessary to suppress superconductivity in superconducting electronics.
Superconductivity (cond-mat.supr-con)
8 pages, 6 figures
Revealing domain wall stability during ultrafast demagnetization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Hung-Tzu Chang, Sergey Zayko, Timo Schmidt, Ofer Kfir, Murat Sivis, Johan H. Mentink, Manfred Albrecht, Claus Ropers
The ultrafast control of nanoscale spin textures such as magnetic domain walls or skyrmions is essential for advancing high-speed, high-density spintronics. However, imaging their dynamics will require a technique that combines nanometer spatial and femtosecond temporal resolution. Introducing ultrafast sub-wavelength imaging in the extreme ultraviolet, we track domain wall properties during ultrafast demagnetization in ferro- and ferrimagnetic thin films. We reveal that domain walls remain invariant in position, shape, and width, down to a demonstrated sub-nanometer precision, for up to 50% demagnetization. Stronger excitation causes stochastic nanoscale domain switching. This previously unobservable robustness of laser-excited domain walls highlights the localized nature of photoinduced demagnetization and presents both challenges and opportunities for all-optical magnetic control. The presented technique can be generalized to directly probe nanoscale dynamics in spintronic materials and devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
23 pages, 12 figures
Spin wave propagation in a ring-shaped magnonic waveguide
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Franz Vilsmeier, Takuya Taniguchi, Michael Lindner, Christian Riedel, Christian Back
We experimentally investigate frequency-selective spin wave (SW) transmission in a micrometre-scale, ring-shaped magnonic resonator integrated with a linear Yttrium Iron Garnet (YIG) stripe. Using super-Nyquist-sampling magneto-optical Kerr effect microscopy (SNS-MOKE) and micro-focused Brillouin light scattering ({\mu}-BLS), we probe SW dynamics in the dipolar regime under in-plane magnetisation. Spatially resolved measurements reveal a sharp transmission peak at 3.92 GHz for an external field of 74 mT, demonstrating strong frequency selectivity.
Our results show that this selectivity arises from scattering and interference between multiple SW modes within the ring. These modes are governed by the anisotropic dispersion relation, transverse mode quantisation due to geometric confinement, and inhomogeneities of the effective magnetic field. In addition, the anisotropy enforces fixed group velocity directions, leading to caustic-like propagation that limits efficient out-coupling. Fourier analysis reveals discrete wavevector components consistent with quantised transverse eigenmodes. Additional {\mu}-BLS measurements at 70 mT show a shift of the transmission peak, confirming that the filtering characteristics are tunable by external parameters.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other)
First-principles open quantum dynamics for solids based on density-matrix formalism
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Jacopo Simoni, Gabriele Riva, Yuan Ping
The theoretical description of materials’ properties driven out of equilibrium has important consequences in various fields such as semiconductor spintronics, nonlinear optics, continuous and discrete quantum information science and technology. The coupling of a quantum many-body system to an external bath can dramatically modify its dynamics compared to that of closed systems, new phenomena like relaxation and decoherence appear as a consequence of the nonunitary evolution of the quantum system. In addition, electron-electron correlations must be properly accounted for in order to go beyond a simple one-electron or mean-field description of the electronic system. Here we discuss a first-principles methodology based on the evolution of the electronic density matrix capable of treating electron-environment interactions and electron-electron correlations at the same level of description. The effect of the environment is separated in a coherent contribution, like the coupling to applied external electro-magnetic fields, and an incoherent contribution, like the interaction with lattice vibrations or the thermal background of radiation. Electron-electron interactions are included using the nonequilibrium Green’s function plus generalized Kadanoff-Baym ansatz. The obtained non-Markovian coupled set of equations reduce to ordinary Lindblad quantum master equation form in the Markovian limit.
Materials Science (cond-mat.mtrl-sci)
Correlated insulating states in slow Dirac fermions on a honeycomb moir{é} superlattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Dongyang Yang, Jing Liang, Haodong Hu, Nitin Kaushal, Chih-En Hsu, Kenji Watanabe, Takashi Taniguchi, Jerry. I Dadap, Zhenglu Li, Marcel Franz, Ziliang Ye
Strong Coulomb repulsion is predicted to open a many-body charge gap at the Dirac point of graphene, transforming the semimetal into a Mott insulator. However, this correlated insulating phase has remained inaccessible in pristine graphene, where a large Fermi velocity dominates the interaction effects. To overcome this limitation, we realize a honeycomb moir{é} superlattice in a twisted MoSe$ _2$ homobilayer, where a graphene-like band structure forms with a Fermi velocity reduced by nearly two orders of magnitude. These slow moir{é} bands are folded from the valence band maximum at the $ \Gamma$ valley of the extended Brillouin zone with negligible spin-orbital coupling, and can therefore simulate massless Dirac fermions in the strongly correlated regime with full SU(2) symmetry. By correlating Rydberg exciton sensing with moir{é} trions of different spatial characters, we detect a Mott gap at the Dirac point that persists up to 110 K. We further identify correlated insulating states at $ \nu=-1$ with a weak ferromagnetic coupling as well as at several fractional fillings. Our results highlight the potential of studying a wide range of quantum many-body phenomena in twisted two-dimensional materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Lowering Insulator-to-Metal Transition Temperature of Vanadium Dioxide Thin Films via Co-Sputtering, Furnace Oxidation and Thermal Annealing
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Vishwa Krishna Rajan, Jeremy Chao, Sydney Taylor, Liping Wang
Thermochromic vanadium dioxide thin films have attracted much attention recently for constructing variable-emittance coatings upon its insulator-metal phase transition for dynamic thermal control. However, fabrication of high-quality vanadium dioxide thin films in a cost-effective way is still a challenge. In addition, the phase transition temperature of vanadium dioxide is around 68°C, which is higher than most of terrestrial and extraterrestrial applications. In this study, we report the fabrication and characterization of tungsten-doped vanadium dioxide thin films with lowered phase transition temperatures via co-sputtering, furnace oxidation and thermal annealing processes for wider application needs. The doping is achieved by co-sputtering of tungsten and vanadium targets while the doping level is varied by carefully controlling the sputtering power for tungsten. Doped thin film samples of 30-nm thick with different tungsten atomic concentrations are prepared by co-sputtering onto undoped silicon wafers. Optimal oxidation time of 4 hours is determined to reach full oxidation in an oxygen-rich furnace environment at 300°C. Systematic thermal annealing study is carried out to find the optimal annealing temperature and time. By using an optical cryostat coupled to an infrared spectrometer, the temperature-dependent infrared transmittance of fully annealed tungsten-doped vanadium dioxide thin films are measured in a wide temperature range from -60°C to 100°C. The phase transition temperature is found to decrease at 24.5°C per at.% of tungsten doping, and the thermal hysteresis between heating and cooling shrinks at 5.5°C per at.% from the fabricated vanadium dioxide thin films with tungsten doping up to 4.1 at.%.
Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
Role of On-site and Inter-site Coulomb Interactions in KV$_3$Sb$_5$: A first-principles DFT+$U$+$V$ study
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
Indukuru Ramesh Reddy, Sayandeep Ghosh, Bongjae Kim, Chang-Jong Kang
Nonlocal Coulomb interactions play a crucial role in stabilizing distinct electronic phases in kagome materials. In this work, we systematically investigate the effects of on-site ($ U$ ) and inter-site ($ V$ ) Coulomb interactions on the electronic structure and stability of charge-density-wave (CDW) phases in the kagome metal KV$ _3$ Sb$ _5$ using density functional theory (DFT+$ U$ +$ V$ ) calculations. We demonstrate that $ V$ promotes the formation and stability of CDW phases, whereas $ U$ suppresses these phases, highlighting a fundamental competition between local and nonlocal electronic correlations. By directly comparing our theoretical results with angle-resolved photoemission spectroscopy (ARPES) data, we identify realistic values of $ U$ and $ V$ that accurately describe the electronic band structure of KV$ _3$ Sb$ _5$ . Our findings establish a detailed $ U$ -$ V$ phase diagram for KV$ _3$ Sb$ _5$ , offering valuable insights into the correlated electronic states in kagome metals and serving as a foundation for future explorations of correlation-driven phenomena in related materials.
Strongly Correlated Electrons (cond-mat.str-el)
8 pages, 5 figures
Why Fe$_3$GaTe$_2$ has higher Curie temperature than Fe$_3$GeTe$_2$?
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Bomin Kim, Tumentsereg Ochirkhuyag, Dorj Odkhuu, S. H. Rhim
Physics of Fe$ _3$ GaTe$ _2$ having higher Curie temperature ($ T_C$ ) than Fe$ _3$ GeTe$ _2$ is explored theoretically in the framework of magnetic exchange interactions. Fe$ _3$ GaTe$ _2$ and Fe$ _3$ GeTe$ _2$ are isostructural, with Fe$ _3$ GaTe$ _2$ having one less valence electron and smaller nearest-neighbor exchange coefficients ($ J_1$ and $ J_2$ ), challenging the conventional notion that larger $ J_1$ or $ J_2$ leads to a higher $ T_C$ . We show that higher order exchange coefficients, $ J_3$ or higher, of Fe$ _3$ GaTe$ _2$ are positive whereas those of Fe$ _3$ GeTe$ _2$ are negative. As a consequence, total sum of all possible exchange coefficients in Fe$ _3$ GaTe$ _2$ are larger than Fe$ _3$ GeTe$ _2$ , which accounts for higher $ T_C$ . To validate these findings, $ T_C$ are computed using both mean-field theory and Monte Carlo simulation. Indeed, higher-order exchange interactions, when properly accounting for the number of neighbors, confirm the higher $ T_C$ of Fe$ _3$ GaTe$ _2$ .
Materials Science (cond-mat.mtrl-sci)
5 pages, 5 figures, one supplementary
Tunable topological phase in 2D ScV$_6$Sn$_6$ kagome material
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Chidiebere I. Nwaogbo, Sanjib K. Das, Chinedu E. Ekuma
We investigate the topological properties of the vanadium-based 2D kagome metal ScV$ _6$ Sn$ _6$ , a ferromagnetic material with a magnetic moment of 0.86 $ \mu_B$ per atom. Using ab initio methods, we explore spin-orbit coupling-induced gapped states and identify multiple Weyl-like crossings around the Fermi energy, confirming a Chern number $ |C| = 1$ and a large anomalous Hall effect (AHE) of 257 $ \Omega^{-1}$ cm$ ^{-1}$ . Our calculations reveal a transition from a topological semimetal to a trivial metallic phase at an electric field strength of $ \approx$ 0.40 eV/Å. These findings position 2D ScV$ _6$ Sn$ _6$ as a promising candidate for applications in modern electronic devices, with its tunable topological phases offering the potential for future innovations in quantum computing and material design.
Materials Science (cond-mat.mtrl-sci)
Quantum effects in rotationally invariant spin glass models
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-04-28 20:00 EDT
Yoshinori Hara, Yoshiyuki Kabashima
This study investigates the quantum effects in transverse-field Ising spin glass models with rotationally invariant random interactions. The primary aim is to evaluate the validity of a quasi-static approximation that captures the imaginary-time dependence of the order parameters beyond the conventional static approximation. Using the replica method combined with the Suzuki–Trotter decomposition, we established a stability condition for the replica symmetric solution, which is analogous to the de Almeida–Thouless criterion. Numerical analysis of the Sherrington–Kirkpatrick model estimates a value of the critical transverse field, $ \Gamma_\mathrm{c}$ , which agrees with previous Monte Carlo-based estimations. For the Hopfield model, it provides an estimate of $ \Gamma_\mathrm{c}$ , which has not been previously evaluated. For the random orthogonal model, our analysis suggests that quantum effects alter the random first-order transition scenario in the low-temperature limit. This study supports a quasi-static treatment for analyzing quantum spin glasses and may offer useful insights into the analysis of quantum optimization algorithms.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Statistical Mechanics (cond-mat.stat-mech), Quantum Physics (quant-ph)
27 pages, 15 figures
Magnetic Resonance Imaging of Single Organic Radicals with Sub-Molecular Resolution
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Gregory Czap, Christoph Wolf, Jose Reina-Gálvez, Mark H. Sherwood, Christopher P. Lutz
Interest in the magnetism of organic compounds is growing because of new organic magnets, spin-based electronics and the diverse properties of magnetic edge states in graphene nanoribbons. Electron spin resonance spectroscopy combined with the scanning tunneling microscopy has recently been developed as a powerful tool to address individual magnetic atoms and molecules at the atomic scale. Here we demonstrate electron spin resonance and magnetic resonance imaging of all-organic radical anions adsorbed on a protective thin insulating film grown on a metal support. We show that using the highly localized exchange field of the magnetic tip apex allows visualization of the delocalized spin density with sub-molecular resolution, enabling spin-density tomography that can distinguish similar molecular species. These results provide new opportunities for visualizing spin density and magnetic interactions at the atomic scale.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Other Condensed Matter (cond-mat.other), Atomic Physics (physics.atom-ph), Chemical Physics (physics.chem-ph)
20 pages, 5 figures
Stability and Response of Vortex Solid Formed in Second Landau Level
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-28 20:00 EDT
Yuto Yokota, Dai Nakashima, Ryusuke Ikeda
Physical properties of the vortex solid phase formed in the second Landau level (2LL), which may be stabilized by strong paramagnetic pairbreaking (PPB), are examined in type II limit with no magnetic screening. First, it is shown that the spectrum of the low energy mode of this vortex solid has the same form as that of the conventional vortex solid in the first (i.e., the lowest) Landau level. Using this result, the melting line of the 2LL vortex solid is examined according to the Lindemann criterion. In contrast to the properties in equlibrium, the electromagnetic response of this vortex solid is quite unusual: Reflecting the presence of antivortices supporting the stability of the lattice structure, the superfluid stiffness measuring the response for a current perpendicular to the magnetic field is found to be nonvanishing, and its sign depends upon the applied current direction. Consequences of this response property are briefly discussed.
Superconductivity (cond-mat.supr-con)
18 pages, 6 figures
Observation of gauge field induced non-Hermitian helical spin skin effects
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Yi Li, Jia-Hui Zhang, Yang Kou, Liantuan Xiao, Suotang Jia, Linhu Li, Feng Mei
Synthetic gauge fields and non-Hermitian skin effects are pivotal to topological phases and non-Hermitian physics, each recently attracting great interest across diverse research fields. Notably, realizing skin effects typically require nonreciprocal couplings or on-site gain and loss. Here, we theoretically and experimentally report that, under gauge fields, non-Hermitian systems with reciprocal couplings and without gain and loss, can nontrivially give rise to an unprecedented nonreciprocal skin effect, featuring helical spin-dependent skin accumulations, dubbed as the ``helical spin skin effect”. Specifically, we construct a lattice model with reciprocal dissipative couplings and gauge fields, implemented in circuit metamaterials. Before introducing the gauge fields, this model exhibits localized spin edge modes and extended bulk modes, without skin effects. As the gauge field strength is applied from $ 0$ to $ \pi$ , we observe the emergence of two distinct spin skin effects and their transitions: the hybrid-order and second-order helical spin skin effects. Furthermore, we show that these effects can be harnessed to realize helical spin-dependent nonreciprocal transmissions. Our findings not only highlight gauge field induced and enriched non-Hermitian topology, but also brings spin-dependent helicity into skin effects and nonreciprocality.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
10 pages, 5 figures,
Phonon-Assisted Radiative Lifetimes and Exciton Dynamics from First Principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Chunhao Guo, Gabriele Riva, Jacopo Simoni, Junqing Xu, Yuan Ping
Exciton-phonon interactions play a fundamental role in phonon-assisted radiative recombination and exciton dynamics in solids. In this work, we present a first-principles framework for computing phonon-assisted radiative lifetimes and exciton dynamics at finite temperatures. Starting from the solution of the Bethe-Salpeter equation, we construct an effective excitonic Hamiltonian that incorporates both exciton-photon and exciton-phonon interactions. Phonon-assisted radiative lifetimes in anisotropic media are evaluated using time-dependent second-order perturbation theory. We further analyze the temperature and phonon-mode dependence of phonon-assisted radiative lifetime and compare our results with available experimental data. We explain the nonmonotonic temperature dependence of the phonon-assisted radiative lifetime by different mechanisms at low and high-temperature regimes. Finally, we perform real-time exciton relaxation at the diagonal approximation of Lindbladian dynamics for time-resolved exciton occupation, providing insights into ultrafast thermalization and scattering pathways. Our ab-initio theory offers a detailed microscopic understanding of phonon-mediated exciton relaxation and recombination processes, and provides in-depth perspectives on phonon-assisted many-body interactions and their influence on optical properties for light-emitting and optoelectronic applications.
Materials Science (cond-mat.mtrl-sci)
DFT Investigations of Major Defects in Quartz Crystal: Implications for Luminescence and ESR Dosimetry and Dating
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Jalaja Pandya, Malika Singhal, Navinder Singh, Naveen Chauhan
Quartz is extensively used for luminescence and ESR dosimetry as well as dating. These techniques use inherent defects introduced in quartz crystal during its crystallization in nature. The defect comprises both intrinsic as well as extrinsic defects. These defects give important luminescence properties to quartz but are not yet well understood from a theoretical perspective. Specifically, in case of luminescence dosimetry the nature of traps and their involvement in luminescence production is not exactly known. Thus, present work attempts to understand the basic physics of defects and their implication for luminescence and ESR techniques via Density Functional Theory (DFT) modelling. The work uses DFT to model the presence of some possible major impurities in quartz. Several interesting novel results are obtained that will have implications for ongoing research in Luminescence and ESR methods. The DFT modelling suggested that Oxygen deficiency in quartz crystal results in the formation of both electron and hole trapping centres. However, it is observed that these centres can be passivated by the introduction of charge compensating OH or H ions. Further, it is found that peroxy defects can be formed in the presence of either excess Oxygen or due to the absence of Silicon (Si4+), however, the nature of the traps formed in both cases is different. Besides these intrinsic defects, Al and Fe are the major impurities which are observed as defects in quartz. The modelling of these impurities suggested that negligible change in DOS is observed for Al defect and Fe generally forms a recombination centre or hole trap. In addition to these, there are several interesting first-time observations that are not reported and will be helpful for progressing luminescence and ESR dosimetry research.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn), Other Condensed Matter (cond-mat.other), Geophysics (physics.geo-ph)
26 pages, 18 figures
Chalcogen Vacancies Rule Charge Recombination in Pnictogen Chalcohalide Solar-Cell Absorbers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Cibrán López, Seán R. Kavanagh, Pol Benítez, Edgardo Saucedo, Aron Walsh, David O. Scanlon, Claudio Cazorla
Pnictogen chalcohalides (MChX, M = Bi, Sb; Ch = S, Se; X = I, Br) represent an emerging class of nontoxic photovoltaic absorbers, valued for their favorable synthesis conditions and excellent optoelectronic properties. Despite their proposed defect tolerance, stemming from the antibonding nature of their valence and conduction bands, their experimentally reported power conversion efficiencies remain below 10%, far from the ideal Shockley-Queisser limit of 30%. Using advanced first-principles calculations and defect sampling techniques, we uncover a complex point-defect landscape in MChX materials, exemplified by BiSeI. Previously overlooked selenium vacancies are identified as critical nonradiative charge-recombination centers, which exist in high concentrations and, although exhibit modest capture coefficients, can reduce the maximum power conversion efficiency of BiSeI down to 24%. We argue that such detrimental effects can be mitigated by cation-poor synthesis conditions and strategic anion substitutions. Building on these insights, and supported by further simulations, we predict BiSBr to be a more defect-tolerant light absorber. This study not only identifies efficiency-limiting factors in MChX but also provides a roadmap for their improvement, paving the way for next-generation solution-processed chalcogenide photovoltaics.
Materials Science (cond-mat.mtrl-sci)
10 pages, 4 figures
Finite-$q$ antiferro and ferri magnetic toroidal order in a distorted kagome structure
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
Akimitsu Kirikoshi, Satoru Hayami
A highly geometrically frustrated lattice structure such as a distorted kagome (or quasikagome) structure enriches physical phenomena through coupling with the electronic structure, topology, and magnetism. Recently, it has been reported that an intermetallic HoAgGe exhibits two distinct magnetic structures with the finite magnetic vector $ q=(1/3,1/3,0)$ : One is the partially ordered state in the intermediate-temperature region, and the other is the kagome spin ice state in the lowest-temperature region. We theoretically elucidate that the former is characterized by antiferro magnetic toroidal (MT) ordering, while the latter is characterized by ferri MT ordering based on the multipole representation theory, which provides an opposite interpretation to previous studies. We also show how antiferro MT and ferri MT orderings are microscopically formed by quantifying the magnetic toroidal moment activated in a multiorbital system. As a result, we find that the degree of distortion for the kagome structure plays a significant role in determining the nature of antiferro MT and ferri MT orderings, which brings about the crossover between the antiferro MT and ferri MT orders. We confirm such a tendency by evaluating the linear magnetoelectric effect. Our analysis can be applied irrespective of lattice structures and magnetic vectors without annoying the cluster origin.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 5 figures in main text + supplemental material
Anisotropic dynamic excitations in a two-dimensional Fulde-Ferrell superfluid
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-28 20:00 EDT
Jinrui Ru, Yanxiang Zhu, Shuning Tan, Huaisong Zhao
By calculating the dynamical structure factor of a two-dimensional (2D) Fulde-Ferrell superfluid system, the anisotropic dynamical excitations are studied systematically using random phase approximation (RPA). Our calculation results not only establish the interaction strength and the Zeeman field dependencies of the phase diagram, but also reveal the evolution of the collective modes and the single-particle excitations during the phase transition from the Bardeen-Cooper-Schrieffer (BCS) superfluid to the FF superfluid, particularly their competition with each other. The calculation results demonstrate that the optimal combination of two parameters (the interaction strength and Zeeman field) exists for finding an FF superfluid. With the increase of the angle between the transferred momentum and the center-of-mass (COM) momentum, the collective phonon mode exhibits a sharp resonance signature at small angles, which gradually diminishes as it merges into the single-particle excitations, then reappears at large angles. In an FF superfluid, the sound speed along the COM momentum direction increases with the Zeeman field strength while decreases with the interaction strength, displaying contrasting behavior compared to a BCS superfluid whereas the sound speed remains nearly constant. Notably, a remarkable roton-like dispersion emerges along the COM momentum direction while it is absent in the opposite direction. These theoretical predictions provide crucial guidance for the experimental search and study of an FF superfluid.
Quantum Gases (cond-mat.quant-gas)
11 pages, 8 figures
Electric-field independent spin-orbit coupling gap in hBN-encapsulated bilayer graphene
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Fang-Ming Jing, Zhen-Xiong Shen, Guo-Quan Qin, Wei-Kang Zhang, Ting Lin, Ranran Cai, Zhuo-Zhi Zhang, Gang Cao, Lixin He, Xiang-Xiang Song, Guo-Ping Guo
The weak spin-orbit coupling (SOC) in bilayer graphene (BLG) is essential for encoding spin qubits while bringing technical challenges for extracting the opened small SOC gap {\Delta}_SO in experiments. Moreover, in addition to the intrinsic Kane-Mele term, extrinsic mechanisms also contribute to SOC in BLG, especially under experimental conditions including encapsulation of BLG with hexagonal boron nitride (hBN) and applying an external out-of-plane electric displacement field D. Although measurements of {\Delta}_SO in hBN-encapsulated BLG have been reported, the relatively large experimental variations and existing experimental controversy make it difficult to fully understand the physical origin of {\Delta}_SO. Here, we report a combined experimental and theoretical study on {\Delta}_SO in hBN-encapsulated BLG. We use an averaging method to extract {\Delta}_SO in gate-defined single quantum dot devices. Under D fields as large as 0.57-0.90 V/nm, {\Delta}_SO=53.4-61.8 {\mu}eV is obtained from two devices. Benchmarked with values reported at lower D field regime, our results support a D field-independent {\Delta}_SO. This behavior is confirmed by our first-principle calculations, based on which {\Delta}_SO is found to be independent of D field, regardless of different hBN/BLG/hBN stacking configurations. Our calculations also suggest a weak proximity effect from hBN, indicating that SOC in hBN-encapsulated BLG is dominated by the intrinsic Kane-Mele mechanism. Our results offer insightful understandings of SOC in BLG, which benefit SOC engineering and spin manipulations in BLG.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Phys. Rev. Applied 23, 044053 (2025)
Dark Superradiance in Cavity-Coupled Polar Molecular Bose-Einstein Condensates
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-28 20:00 EDT
Yuqi Wang, Su Yi, Yuangang Deng
We propose an experimental scheme to realize phase transition from {\it dark superradiance} to conventional superradiance in a microwave cavity coupled to polar molecules. The competition between cavity-mediated infinite-range repulsions and finite-range attractive dipolar interactions stabilizes a variety of exotic quantum phases, including vortex, vortex anti-vortex pairs, and superradiant phase, all emerging without external driving fields. In vortex phase associated with {\it dark superradiance}, cavity remains in vacuum state while profoundly reshaping the condensate’s ground-state wave functions. In particular, the spin configuration locally parallel but globally anti-parallel is a direct consequence of competing for two nonlocal interactions. Beyond Dicke paradigm, dipolar dressing of condensate enables access to an unexplored regime of repulsion-dominated superradiance. A Bogoliubov analysis of low-energy excitation spectrum confirms that the condensate remains stable, avoiding roton-maxon induced collapse even in strongly dipolar regime.
Quantum Gases (cond-mat.quant-gas)
8+8 pages, 5+1 figures,
Higher-order topological corner states and edge states in grid-like frames
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Yimeng Sun, Jiacheng Xing, Li-Hua Shao, Jianxiang Wang
Continuum grid-like frames composed of rigidly jointed beams, wherein bending is the predominant deformation mode, are classic subjects of study in the field of structural mechanics. However, their topological dynamical properties have only recently been revealed. As the structural complexity of the frame increases along with the number of beam members arranged in the two-dimensional plane, the vibration modes also increase significantly in number, with frequency ranges of topological states and bulk states overlapped, leading to hybrid mode shapes. Therefore, concise theoretical results are necessary to guide the identification of topological modes in such planar continuum systems with complex spectra. In this work, within an infinitely long frequency spectrum, we obtain analytical expressions for the frequencies of higher-order topological corner states, edge states, and bulk states in kagome frames and square frames, as well as the criteria of existence of these topological states and patterns of their distribution in the spectrum. Additionally, we present the frequency expressions and the existence criterion for topological edge states in quasi-one-dimensional structures such as bridge-like frames, along with an approach to determine the existence of topological edge states based on bulk topological invariants. These theoretical results fully demonstrate that the grid-like frames, despite being a large class of continuum systems with complex spectra, have topological states (including higher-order topological states) that can be accurately characterized through concise analytical expressions. This work contributes to an excellent platform for the study of topological mechanics, and the accurate and concise theoretical results facilitate direct applications of topological grid-like frame structures in industry and engineering.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Classical Physics (physics.class-ph)
Extremely asymmetric diffraction as a method of determining magneto-optical constants for X-rays near absorption edges
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
M A Andreeva (MSU), Yu. Repchenko, A G Smekhova (MSU), Karine Dumesnil (IJL), F. Wilhelm (ESRF), A. Rogalev (ESRF)
The spectral dependence of the Bragg peak position under conditions of extremely asymmetric diffraction has been analyzed in the kinematical and dynamical approximations of the diffraction theory. Simulations have been performed for the L$ _3$ absorption edge of yttrium in a single crystal YFe$ _2$ film; they have shown that the magneto optical constants (or, equivalently, the dispersion corrections to the atomic scatter ing factor) for hard X rays can be determined from this dependence. Comparison with the experimental data obtained for a Nb(4 nm)/YFe$ _2$ (40 nm $ \langle 110 \rangle$ )/Fe(1.5 nm)/Nb(50 nm)/sapphire sample at the European Synchrotron Radiation Facility has been made.
Materials Science (cond-mat.mtrl-sci)
in Russian language
Journal of Experimental and Theoretical Physics (JETP) / Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki, 2015, 120 (6), pp.974-981
Enhanced Backgate Tunability on Interfacial Carrier Concentration in Ionic Liquid-Gated MoS2 Devices
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Qiao Chen, Chengyu Yan, Changshuai Lan, Qiyang Song, Yi Yan, Shun Wang
The periodic spatial modulation potential arising from the zig-zag distribution of ions at large gate voltage in an ionic liquid gated device may enable functionalities in a similar way as nanopatterning and moiré engineering. However, the inherent coupling between periodic modulation potential and carrier concentration in ionic liquid devices has hindered further exploration. Here, we demonstrate the feasibility of decoupling manipulation on periodic modulation potential and carrier density in an ionic liquid device by using a conventional backgate. The backgate is found to have a tunability on carrier concentration comparable to that of ionic gating, especially at large ionic liquid gate voltage, by activating the bulk channels mediated back tunneling between the trapped bands and interfacial channel.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 4 figures
Small, 2025
The structural effects of (111) growth of La$_2$CoMnO$_6$ on SrTiO$_3$ and LSAT – new insights from 3D crystallographic characterisation with 4D-STEM and Digital Dark Field imaging
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Ian MacLaren, Andrew T. Fraser, Matthew R. Lipsett
The 3-dimensional orientation of La atom modulations has been mapped in two thin films of La$ _2$ CoMnO$ _6$ grown on SrTiO$ _3$ and LSAT ([La,Sr,Al,Ta] oxide) using a 4D-scanning transmission electron microscopy (4D-STEM) method based on the recently developed Digital Dark Field method. This images the shifts of diffraction spots and the azimuthal intensity distribution in the First Order Laue Zone, and then uses them to reconstruct and map the 3D crystallography. This clearly shows a flip from out-of-plane modulation with tensile strain on SrTiO3 to in-plane modulation with compressive strain on LSAT. This hitherto unobserved crystallographic change had a significant influence on the out-of-plane lattice parameter which left more room for the full incorporation of the larger CoO6 octahedra on LSAT and therefore explained the improved Mn-Co ordering and better properties for this film. Moreover, the method would be applicable to many other systems of epitaxial growth of complex oxides, revealing crystallographic details of crucial importance to properties which are not visible in conventional atomic resolution imaging.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Graphene Enhanced Resonant Raman Spectroscopy of Gallium Nitride Nanocrystals
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Marek Kostka, Jindřich Mach, Miroslav Bartošík, David Nezval, Martin Konečný, Vojtěch Mikerásek, Linda Supalová, Jakub Piastek, Tomáš Šikola
The scattering of lattice excitations (phonons) with the photoexcited charge carriers is of a major concern in optoelectronic devices. Here, the resonant Raman scattering will be utilized to study an exciton-phonon interaction in GaN nanocrystals, further enhanced by the underlying graphene. Raman spectroscopy using various excitation energies shows how the exciton-phonon interaction behaves, unveiling the scattering strength. The origin of the interaction is in the condition of resonance, which is directly observed in the temperature resolved spectra. Most importantly, the underlying graphene strongly enhances the coupling of phonons and excitons. Consequently, an enhanced resonant Raman spectrum of GaN nanocrystals possessing clearly observable phonon overtones up to the 4th order has been obtained. It has been demonstrated that the responsible effect is the electron transfer between nanocrystals and the underlying graphene. The utilization of such an increased coupling effect can be beneficial for a study of the charge carrier scattering in semiconducting nanomaterials, analysis of their crystal quality, improvement of sensor sensitivity and in the subsequent development of new-generation optoelectronic devices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
How ferromagnetic plane drives magnetocrystalline anisotropy in antiferromagnetic CoO and FeO
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Ilya V. Kashin, Alexander S. Iakovlev, Sergei N. Andreev
In this study we present a theoretical investigation of the role that ferromagnetic plane (111) plays in the formation of magnetocrystalline anisotropy (MCA) effects in CoO and FeO monoxides. For this purpose, a first-principles calculations of the electronic structure is performed within the GGA$ +U$ approach. Based on the low-energy model in the Wannier functions basis, the MCA energy angular profile and the isotropic exchange environment of the transition metal atom are estimated using $ \bf{k}$ -dependent Green’s functions. We have revealed a clear regularity in the direction of the easy and hard axes in both systems as lying in the (111) plane or along [111]. While for CoO the easy / hard axis orientation is (111) / [111], for FeO it appears reversed and thus emphasises the fundamental importance of (111) as the geometrical driver of the magnetism in the crystals. The identification of the contributions that individual sublattices make to the MCA energy allowed us to reveal the decisive role of the electron hopping mechanisms in easy axis orientation. Considering the MCA and exchange environment with orbital decomposition in CoO and FeO under directional pressure in the (111) plane and along [111] showed a direct interrelation between the ferro- and antiferromagnetic contributions to the exchange environment and the energetic stability of the easy axis.
Materials Science (cond-mat.mtrl-sci)
17 pages, 5 figures
Monitoring charge separation of individual cells in perovskite/silicon tandems via transient surface photovoltage spectroscopy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Maxim Simmonds, Ke Xu, Steve Albrecht, Lars Korte, Igal Levine
Identification of charge carrier separation processes in perovskite/silicon tandem solar cells and recombination at buried interfaces of charge selective contacts is crucial for photovoltaic research. Here, intensity- and wavelength- dependent transient surface photovoltage (tr-SPV) is used to investigate slot-die-coated perovskite top layers deposited on n-type Heterojunction Silicon bottom cells. We show that using an appropriate combination of photon energy and/or bottom cell polarity, one can individually probe the buried interfaces of the bottom silicon cell or the perovskite`s buried interfaces of a tandem solar cell: For excitation with higher energy photons, time delays before the onset of a strong SPV signal indicate significant hole minority drift before separation in the silicon bottom cells. Furthermore, symmetric bottom Si heterojunction solar cell stacks can serve to investigate the top perovskite stack including its junction to the bottom cell, unhampered by photovoltages from the silicon substrate. Thus, investigation of the buried interfaces in tandem devices using time-resolved surface photovoltage is found to yield valuable information on charge carrier extraction at buried interfaces and demonstrates its unique potential compared to more conventional approaches that rely on photoluminescence decay kinetics.
Materials Science (cond-mat.mtrl-sci)
Acoustic phonons, spin-phonon coupling and spin relaxation via the lattice reorientation mechanism in hexagonal germanium nanowires
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Baksa Kolok, György Frank, András Pályi
Spin relaxation via electron-phonon interaction is an important decoherence mechanism for spin qubits. In this work, we study spin relaxation in hexagonal (2H) germanium, a novel direct-gap semiconductor showing great potential to combine highly coherent spin qubits with optical functionality. Focusing on electrostatically defined quantum dots in hexagonal germanium nanowires, we (i) identify geometries where spin qubit experiments are feasible, (ii) compute the nanowire phonon modes, and (iii) describe spin relaxation of hole spin qubits due to phonon-induced lattice reorientation, a direct spin-phonon coupling mechanism that is absent in cubic semiconductors typically used for spin qubits (GaAs, cubic Si, cubic Ge). We obtain the spin relaxation time as a function of nanowire cross section, quantum dot confinement length, and magnetic field. For realistic parameters, we find relaxation times above 10 ms, and reveal that the magnetic field direction maximizing the relaxation time depends on the qubit Larmor frequency. Our results facilitate the design of nanowire quantum dot experiments with long qubit relaxation times.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
11 pages, 4 figures, 7 pages appendix
Quantum droplets in a beyond-mean-field density-dependent gauge theory
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-04-28 20:00 EDT
Matthew Edmonds, Patrik Öhberg
The beyond-mean-field corrections appropriate to a bosonic many-body system experiencing a density-dependent gauge potential are derived, and from this the dimensional hierarchy of quantum droplet solutions are explored. Non-stationary quantum droplet solutions are supported by a single interaction parameter characterising the strength of the gauge potential, while in one dimension the beyond-mean-field theory can be solved exactly to yield chiral quantum droplets and dark soliton-like excitations. Numerical simulations of single and pairs of chiral droplets indicate a rich dynamics in the beyond-mean-field regime.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
8 pages, 3 figures. Comments welcome
Topological phases of coupled Su-Schrieffer-Heeger wires
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
The phase diagrams of arbitrary number $ N_{\text{w}}$ of diagonally and perpendicularly coupled Su-Schrieffer-Heeger wires have been identified. The diagonally coupled wires have rich topological phase diagrams exhibiting insulating phases with winding numbers $ 0\leq w \leq N_{\text{w}}$ and topological critical lines restricted by the reflection mirror symmetry. Even number of perpendicularly coupled wires exhibit either gapless or trivial topological phases. Odd number of perpendicularly coupled wires additionally exhibit nontrivial topological phases with winding number $ w=1$ . Due to the mirror reflection symmetry, their gapless regions can be topologically nontrivial. Odd number of perpendicularly coupled wires reveal coherent confined correlations in the odd indexed wires away from the gapless regions.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Multi-site mixing and entropy stabilization of CsPbI$_{3}$ with potential application in photovoltaics
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Namitha Anna Koshi, Krishnamohan Thekkepat, Doh-Kwon Lee, Seung-Cheol Lee, Satadeep Bhattacharjee
Metal halide perovskite solar cells have achieved dramatic improvements in their power conversion efficiency in the recent past. Since compositional engineering plays an important role in optimizing material properties, we investigate the effect of alloying at Cs and Pb sites on the energetics and electronic structure of CsPbI$ _{3}$ using cluster expansion method in combination with first-principles calculations. For Ge-mixing at Pb-site, the $ \alpha$ and $ \beta$ -phases are considered with emphasis on the electronic structure, transition probability, absorption coefficient, efficiency, and carrier mobility of higher-symmetry configurations. CsPb$ _{0.50}$ Ge$ _{0.50}$ I$ _{3}$ (Cs$ _{2}$ PbGeI$ _{6}$ ) which takes up a double perovskite (elpasolite) structure has a direct band gap with no parity-forbidden transitions. Further, we utilize the alloy entropic effect to improve the material stability and optoelectronic properties of CsPbI$ _{3}$ by multi-element mixing. For the proposed mixed compositions, the Fr{ö}hlich electron-phonon coupling constant is determined. Scattering rates and electron mobility are obtained from first-principles inputs. These lower Pb-content inorganic perovskites offer great promise as efficient solar cell materials for photovoltaic applications.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
Translocation of Active Polymerlike Worms
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-28 20:00 EDT
Marin Vatin, Rosa Sinaasappel, Renske Kamping, Chantal Valeriani, Emanuele Locatelli, Antoine Deblais
Active polymer translocation through confined spaces is a key biological process underlying DNA transport through nuclear pores and actin filament dynamics in cell migration. Here, we use living polymer-like Tubifex tubifex worms as a model system to explore how contour length and activity-modulated via environmental temperature-affect translocation dynamics in confined geometries. Using 3D-printed chambers connected by a narrow bridge, we track worm conformation and motion under confinement. In contrast to passive polymers, contour length has no influence, while activity strongly modulates escape dynamics. At an intermediate temperature of 20°C, an optimal balance between directed propulsion and reorientation-characterized by the Péclet number-maximizes translocation efficiency. Our findings suggest that active filaments achieve optimal exploration of confined spaces at intermediate activity levels. We further validate our results through simulations of tangentially driven polymer models which quantitatively reproduce the experimental findings at ambient temperature.
Soft Condensed Matter (cond-mat.soft)
6 pages, 4 figures
Dressed basis sets for the modeling of exchange interactions in double quantum dots
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Mauricio J. Rodríguez, Esteban A. Rodríguez-Mena, Ahmad Fouad Kalo, Yann-Michel Niquet
We discuss the microscopic modeling of exchange interactions between double semiconductor quantum dots used as spin qubits. Starting from a reference full configuration interaction (CI) calculation for the two-particle wave functions, we build a reduced basis set of dressed states that can describe the ground-state singlets and triplets over the whole operational range with as few as one hundred basis functions (as compared to a few thousands for the full CI). This enables fast explorations of the exchange interactions landscape as well as efficient time-dependent simulations. We apply this methodology to a double hole quantum dot in germanium, and discuss the physics of exchange interactions in this system. We show that the net exchange splitting results from a complex interplay between inter-dot tunneling, Coulomb exchange and correlations. We analyze, moreover, the effects of confinement, strains and Rashba interactions on the anisotropic exchange and singlet-triplet mixings at finite magnetic field. We finally illustrate the relevance of this methodology for time-dependent calculations on a singlet-triplet qubit.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 13 figures
The impact of electrical contacts on the optical properties of a MoS$_{2}$ monolayer
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-04-28 20:00 EDT
Agata Zielińska, Mateusz Dyksik, Alessandro Surrente, Jonathan Eroms, Dieter Weiss, Paulina Płochocka, Mariusz Ciorga
Achieving high performance in transition-metal-dichalcogenide-based optoelectronic devices is challenging – the realization of an efficient electrical contacting scheme should not be obtained at the expense of their optical quality. Here we present the optical properties of MoS$ _{2}$ monolayers which have been electrically contacted with bismuth and gold. The photoluminescence (PL) spectrum of the samples contacted with both materials is significantly broadened. In the case of the bismuth contacted sample we note an additional, low energy band in the PL spectrum, attributed to a defect state formed during the evaporation of Bi. Comparing the intensity of the excitonic peak and of the defect-related peak, we note that there is a correlation between the type of contacts and the optical properties.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Main text: 6 pages, 4 figures; Supplemental: 6 pages, 4 figures. Submitted to Applied Physics Letters
Orientation- and pressure-dependence of the vibrational response of a monolayer crystal on a vicinal diamond surface
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Yi Zhao, Lingxiao Zhao, Chengjiang Du, Ruirui Liu, John A. McGuire, Yanpeng Qi
We systematically investigate polarization-dependent Raman spectra of a monolayer crystal of WS2 on the (100) and (230) surfaces of diamond. At ambient pressure, identical polarization dependence of the Raman spectra is observed on the different surfaces, independent of the orientation of the monolayer crystal relative to the diamond crystal. However, when monolayer WS2 is compressed to about 4 GPa, an abrupt drop of the intensity of the 2LA mode relative to the A’ mode occurs on the (100) surface and the (230) surface with the zigzag direction along the atomic step edges of the (230) surface. In contrast, no such drop is observed when the armchair direction is along or at 15° to the atomic steps of the (230) surface. We also observe a shift of the polarization angle of the intensity maxima of the 2LA and A’ modes on (230) surface during compression. These results demonstrate that the atomic steps of a vicinal surface strongly modify the vibrational response under high pressure.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Superconductivity (cond-mat.supr-con)
14 pages,5 figures
ACS Applied Electronic Materials 2025
Valley Polarization and Anomalous Valley Hall Effect in Altermagnet Ti2Se2S with Multipiezo Properties
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Xin Hu, Weihang Zhao, Wenjun Xia, Hanbo Sun, Chao Wu, Yin-Zhong Wu, Ping Li
Recently, altermagnets demonstrate numerous newfangle physical phenomena due to their inherent antiferromagnetic coupling and spontaneous spin splitting, that are anticipated to enable innovative spintronic devices. However, the rare two-dimensional altermagnets have been reported, making it difficult to meet the requirements for high-performance spintronic devices on account of the growth big data. Here, we predict a stable monolayer Ti2Se2S with out-of-plane altermagnetic ground state and giant valley splitting. The electronic properties of altermagnet Ti2Se2S are highly dependent on the onsite electron correlation. Through symmetry analysis, we find that the valleys of X and Y points are protected by the mirror Mxy symmetry rather than the time-reversal symmetry. Therefore, the multipiezo effect, including piezovalley and piezomagnetism, can be induced by the uniaxial strain. The total valley splitting of monolayer Ti2Se2S can be as high as ~500 meV. Most interestingly, the direction of valley polarization can be effectively tuned by the uniaxial strain, based on this, we have defined logical “0”, “+1”, and “-1” states for data transmission and storage. In addition, we have designed a schematic diagram for observing the anomalous Hall effect in experimentally. Our findings have enriched the candidate materials of two-dimensional altermagnet for the ultra-fast and low power consumption device applications.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 6 figures
Anomalous Hall effect in antiferromagnetic RGaGe (R = Nd, Gd) single crystals
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-28 20:00 EDT
Weizheng Cao, Yuze Xu, Yi Liao, Cuiying Pei, Juefei Wu, Qi Wang, Yanpeng Qi
Recently, the non-centrosymmetric Weyl semimetallic candidate family RTX (R = rare-earth element, T= poor metal, X = Si and Ge) has recently attracted significant attention due to its exotic quantum states and potential applications in quantum devices. In this study, our comprehensive investigations of high-quality NdGaGe and GdGaGe single crystals reveal distinct magnetic and electrical responses. Both compounds exhibit antiferromagnetic transitions with TN - 7.6 K and 22.4 K for NdGaGe and GdGaGe, respectively. NdGaGe exhibits strong magnetic anisotropy (\c{hi}c /\c{hi}a - 70). In contrast, GdGaGe displays weak magnetic anisotropic behavior (\c{hi}c /\c{hi}a - 1) with a distinctive spin-flop transition. Below TN, NdGaGe shows significant negative magnetoresistance due to the reduced spin-disorder scattering arising from the field-induced spin alignment. GdGaGe exhibits more complex magnetoresistance behavior: positive values at low fields transitioning to negative values attributed to the reduced spin-flop scattering. Specially, NdGaGe demonstrates a large anomalous Hall conductance (AHC) of approximately 368 {\Omega}-1 cm-1, which is dominated by the intrinsic mechanism. These reveal the pivotal role of rare-earth elements in modulating the electronic structure, magnetic properties, and transport characteristics of the RGaGe system, thereby providing valuable insights for developing next-generation spintronic devices.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
14 pages,4 figures
Computational search for materials having a giant anomalous Hall effect in the pyrochlore and spinel crystal structures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Sean Sullivan, Seungjun Lee, Nathan J. Szymanski, Amil Merchant, Ekin Dogus Cubuk, Tony Low, Christopher J. Bartel
Ferromagnetic pyrochlore and spinel materials with topological flat bands are of interest for their potential to exhibit a giant anomalous Hall effect (AHE). In this work, we present computational predictions of stability and electronic structure for 448 compositions within the pyrochlore (A2B2O7) and spinel (AB2O4) frameworks. Of these, 92 are predicted to be thermodynamically stable or close (< 100 meV/atom) to the convex hull, with trends deviating from expectations based on ionic radius-ratio rules. Among these 92 materials, 13 are predicted to adopt a ferromagnetic ground state at 0 K. Two additional materials meeting these criteria were also identified from open materials databases. Calculations of anomalous Hall angles (AHA) and conductivities reveal that 11 out of these 15 materials are promising candidates for spintronic applications requiring high electronic conductivity and a giant AHE. Our results suggest that the AHA can be further enhanced by tuning the Fermi level, for example through chemical doping. Using this approach, we identify five materials whose AHA may exceed 0.2. Notably, In2Ir2O7 exhibits an exceptionally high AHA of 0.728 when its Fermi level is optimized. These findings provide a roadmap for the targeted synthesis of new pyrochlore and spinel compounds with enhanced AHE properties. They also broaden the compositional design space for these structures and support the discovery of high-performance materials for next-generation spintronic applications.
Materials Science (cond-mat.mtrl-sci)
The possible frustrated superconductivity in the kagome superconductors
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-28 20:00 EDT
Hong-Min Jiang, Wen-Qian Dong, Shun-Li Yu, Z. D. Wang
Geometric frustration has long been a subject of enduring interest in condensed matter physics. While geometric frustration traditionally focuses on magnetic systems, little attention is paid to the “frustrated superconductivity” which could arise when the superconducting interaction conflicts with the crystal symmetry. The recently discovered kagome superconductors provide a particular opportunity for studying this due to the fact that the frustrated lattice structure and the interference effect between the three sublattices can facilitate the frustrated superconducting interaction. Here, we propose a theory that supports the frustrated superconducting state, derived from the on-site $ s$ -wave superconducting pairing in conjunction with the nearest-neighbor pairings hoping and the unique geometrical frustrated lattice structure. In this state, whereas the mutual $ 2\pi/3$ difference of the superconducting pairing phase causes the six-fold modulation of the amplitude and breaks the time-reversal symmetry with $ 4\pi$ phase changes of the superconducting pairing as one following it around the Fermi surface, it is immune to the impurities without the impurity-induced in-gap states and produces the pronounced Hebel-Slichter peak of the nuclear spin-lattice relaxation rate below $ T_{c}$ . Notably, the theory also reveals a disorder-induced superconducting pairing transition from the frustrated superconducting state to an isotropic $ s$ -wave superconducting state without traversing the nodal points, recovering and explaining the behavior found in experiment. This study not only serves as a promising proposal to mediate the divergent or seemingly contradictory experimental outcomes regarding superconducting pairing symmetry, but may also pave the way for advancing investigations into the frustrated superconducting state.
Superconductivity (cond-mat.supr-con)
10 pages, 5 figures
Coupled-wire Construction of a Non-crystalline Fractional Quantum Hall Effect
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
Justin Schirmann, Peru d’Ornellas, Adolfo G. Grushin
The fractional quantum Hall effect, a paradigmatic topologically ordered state, has been realised in two-dimensional strongly correlated quantum gases and Chern bands of crystals. Here we construct a non-crystalline analogue by coupling quantum wires that are not periodically placed in real-space. Remarkably, the model remains solvable using bosonisation techniques. Due to the non-uniform couplings between the wires, the ground state has different degeneracy compared to the crystalline case. It displays a rich phenomenology of excitations, which can either behave like anyons confined to move in one dimension (lineons), anyons confined to hop between two wires (s-lineons), and anyonic excitations that are free to travel across the system. Both the ground state degeneracy and mutual statistics are directly determined by the real-space positions of the wires. By providing an analytically solvable model of a non-crystalline fractional quantum Hall effect, our work showcases that topological order can display richer phenomenology beyond crystals. More broadly, the non-uniform wire construction we develop can serve as a tool to explore richer many-body phenomenology in non-crystalline systems.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
18 pages, 9 figures
More is less in unpercolated active solids
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-28 20:00 EDT
Jack Binysh, Guido Baardink, Jonas Veenstra, Corentin Coulais, Anton Souslov
A remarkable feat of active matter physics is that systems as diverse as collections of self-propelled particles, nematics mixed with molecular motors, and interacting robots can all be described by symmetry-based continuum theories. These descriptions rely on reducing complex effects of individual motors to a few key active parameters, which increase with activity. Here we discover a striking anomaly in the continuum description of non-reciprocal active solids, a ubiquitous class of active materials. We find that as microscopic activity increases, macroscale active response can vanish: more is less. In this highly active regime, non-affine and localized modes prevail and destroy the large-scale signature of microscopic activity. These modes exist in any dilute periodic structure and emerge in random lattices below a percolation transition. Our results unveil a counterintuitive facet of active matter, offering new principles for engineering materials far from equilibrium.
Soft Condensed Matter (cond-mat.soft), Statistical Mechanics (cond-mat.stat-mech)
17 pages including Methods, 8 figures. See this https URL for Supplementary Movies
Anisotropic Piezomagnetism in Noncollinear Antiferromagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Vu Thi Ngoc Huyen, Yuki Yanagi, Michi-To Suzuki
In 3d-electron magnetic systems, the magnetic structures that transform each other by spin rotation have very close degenerate energies due to small spin-orbit coupling and can be easily controlled by chemical substitution and external magnetic fields. We investigate anisotropic piezomagnetic effects, exhibiting the different magnetic responses depending on the type of strain and the magnetic structures, for non-collinear magnetic states in Mn$ _3A$ N ($ A=$ Ni, Cu, Zn, Ga) and Mn$ _3X$ ($ X$ = Sn and Ge) based on detailed symmetry analysis using spin group and magnetic group and first-principles calculations of piezomagnetic responses. In Mn$ _3A$ N, magnetization develops along two distinct directions under the same applied stress, corresponding to two AFM states connected by spin rotation. Analysis of the piezomagnetic tensor based on magnetic and spin point groups for the states with and without spin-orbit coupling, respectively, shows that the difference in the magnitude of magnetization along different directions is attributed to the spin-orbit coupling. Mn$ _3X$ are known to stabilize different AFM structures in the directions of the applied in-plane magnetic fields. Under uniaxial stress along the orthorhombic $ x$ and $ y$ axes, magnetization is induced without breaking the magnetic symmetry, but it develops in the opposite direction due to exchange interaction. Our study demonstrates that the direction and sign of strain-induced magnetization in Mn$ _3A$ N and Mn$ _3X$ can be effectively controlled by strain in combination with magnetic fields. These findings highlight the potential for strain-tunable magnetic devices in noncollinear AFMs.
Materials Science (cond-mat.mtrl-sci)
20 pages, 17 figures
Ab initio modeling of TWIP and TRIP effects in $β$-Ti alloys
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
David Holec, Johann Grillitsch, Jose L. Neves, David Obersteiner, Thomas Klein
Transformations in bcc-$ \beta$ , hcp-$ \alpha$ , and the $ \omega$ phases of Ti alloys are studied using Density Functional Theory for pure Ti and Ti alloyed with Al, Si, V, Cr, Fe, Cu, Nb, Mo, and Sn. The $ \beta$ -stabilization caused by alloying Si, Fe, Cr, and Mo was observed, but the most stable phase appears between the $ \beta$ and the $ \alpha$ phases, corresponding to the martensitic $ \alpha’’$ phase. Next, the $ {112}\langle11\bar1\rangle$ bcc twins are separated by a positive barrier, which further increases by alloying w.r.t. pure Ti. The $ {332}\langle11\bar3\rangle$ twinning yields negative barriers for all species but Mo and Fe. This is because the transition state is structurally similar to the $ \alpha$ phase, which is preferred over the $ \beta$ phase for the majority of alloying elements. Lastly, the impact of alloying on twin boundary energies is discussed. These results may serve as design guidelines for novel Ti-based alloys with specific application areas.
Materials Science (cond-mat.mtrl-sci)
26 pages, 8 figures
Bridging the Gap Between Avalanche Relaxation and Yielding Rheology
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-28 20:00 EDT
Leonardo Relmucao-Leiva, Carlos Villarroel, Gustavo Düring
The yielding transition in amorphous materials, whether driven passively (simple shear) or actively, remains a fundamental open question in soft matter physics. While avalanche statistics at the critical point have been extensively studied, the emergence of the dynamic regime at yielding and the steady-state flow properties remain poorly understood. In particular, the significant variability observed in flow curves across different systems lacks a clear explanation. We introduce the Controlled Relaxation Time Model (CRTM), a novel simulation framework that treats relaxation time as a tunable parameter, seamlessly bridging quasistatic avalanche statistics and dynamic flow regimes. CRTM reproduces known results in both limits and enables direct analysis of the transition between them, providing precise measurements of avalanche relaxation times. Applying CRTM to different microscopic dynamics, we find that a previously proposed scaling relation connecting critical exponents holds for passive systems. However, active systems exhibit significant deviations, suggesting a missing ingredient in the current understanding of active yielding.
Soft Condensed Matter (cond-mat.soft)
Analytic solution for the nonlinear response of magnetic nanoparticles to large amplitude oscillatory fields
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-04-28 20:00 EDT
Nonlinear responses of physical systems to strong perturbations are notoriously difficult to tackle analytically. Here, we present analytic results for the nonlinear response of magnetic nanoparticles to large amplitude oscillatory magnetic fields based on a particular model for the magnetization dynamics. A number of characteristic features of the in-phase and out-of-phase higher-harmonic response are found and analyzed. In particular we find that the magnitude of higher harmonic contributions Rn depends on the field amplitude and frequency only via a single scaling variable that combines the two quantities. The decrease of |Rn|with increasing order nof harmonics is a key quantity monitored in biomedical applications such as magnetic particle spectroscopy and magnetic particle imaging. Except for the first few harmonics, we find that this decrease is exponential with a rate that depends on the scaling variable only. For not too high frequencies and not loo large amplitudes, we find that these exact results for one particular model of magnetization dynamics hold approximately also for other, more frequently used models. Our results therefore offer not only deeper insight into strongly nonlinear responses of magnetic nanoparticles, especially for higher harmonics that are very difficult to determine numerically, but also suggest analyzing data in terms of a scaling variable.
Soft Condensed Matter (cond-mat.soft)
13 pages, 7 figures; accepted for publication in Phys Rev E 2025
Interface phonon modes governing the ideal limit of thermal transport across diamond/cubic boron nitride interfaces
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Xiaonan Wang, Xin Wu, Penghua Ying, Zheyong Fan, Huarui Sun
Understanding the ideal limit of interfacial thermal conductance (ITC) across semiconductor heterointerfaces is crucial for optimizing heat dissipation in practical applications. By employing a highly accurate and efficient machine-learned potential trained herein, we perform extensive non-equilibrium molecular dynamics simulations to investigate the ITC of diamond/cubic boron nitride ($ c$ BN) interfaces. The ideal diamond/$ c$ BN interface exhibits an unprecedented ITC of 11.0 $ \pm$ 0.1 GW m$ ^{-2}$ K$ ^{-1}$ , setting a new upper bound for heterostructure interfaces. This exceptional conductance originates from extended phonon modes due to acoustic matching and localized C-atom modes that propagate through B-C bonds. However, atomic diffusion across the ideal interface creates mixing layers that disrupt these characteristic phonon modes, substantially suppressing the thermal transport from its ideal limit. Our findings reveal how interface phonon modes govern thermal transport across diamond/$ c$ BN interfaces, providing insights for thermal management in semiconductor devices.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
11 pages, 7 figures
Nature of the 1/3 Magnetization Plateau in Spin-1/2 Kagome Antiferromagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-04-28 20:00 EDT
Li-Wei He, Xinzhe Wang, Shun-Li Yu, Jian-Xin Li
We investigate the origin of the 1/3 magnetization plateau in the $ S=1/2$ kagome antiferromagnetic Heisenberg model using the variational Monte Carlo and exact diagonalization methods, to account for the recent experimental observations in YCu$ _3$ (OH)$ _{6+x}$ Br$ _{3-x}$ and YCu$ _3$ (OD)$ _{6+x}$ Br$ _{3-x}$ . We identify three degenerate valence-bond-solid (VBS) states forming a $ \sqrt{3} \times \sqrt{3}$ unit cell. These states exhibit David-star patterns in the spin moment distribution with only two fractional values $ -1/3$ and $ 2/3$ , and are related through translational transformations. While the spin correlations in these VBS states are found to be short-range, resembling a quantum spin liquid, we show that they have a vanishing topological entanglement entropy and thus are topologically trivial many-body states. Our theoretical results provide strong evidence that the 1/3 magnetization plateau observed in recent experiments arises from these $ \sqrt{3} \times \sqrt{3}$ VBS states with fractional spin moments.
Strongly Correlated Electrons (cond-mat.str-el)
submmited to Chinese Physics Letters
Terahertz time-domain spectroscopy of materials under high pressure in a diamond anvil cell
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-04-28 20:00 EDT
Tim Suter, Zia Macdermid, Zekai Chen, Steven Lee Johnson, Elsa Abreu
We present the combination of a broadband terahertz time-domain spectroscopy system (0.1 - 8 THz), a diamond anvil cell capable of generating high pressure conditions of up to 10 GPa and a cryostat reaching temperatures as low as 10 K. This combination allows us to perform equilibrium and time-resolved THz spectroscopy measurements of a sample while continuously tuning its temperature and pressure conditions. In this work, the procedures and characterizations necessary to carry out such experiments in a tabletop setup are presented. Due to the large modifications of the terahertz beam as it goes through the diamond anvil cell (DAC), standard terahertz time-domain spectroscopy analysis procedures are no longer applicable. New methods to extract the pressure dependent material parameters are presented, both for samples homogeneously filling the DAC sample chamber as well as for bulk samples embedded in pressure media. Different pressure media are tested and evaluated using these new methods, and the obtained material parameters are compared to literature values. Time resolved measurements under pressure are demonstrated using an optical pump - THz probe scheme.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Comment on “Superconductivity and Mott Physics in Organic Charge Transfer Materials”
New Submission | Superconductivity (cond-mat.supr-con) | 2025-04-28 20:00 EDT
Rupali Jindal, Sumit Mazumdar, R. Torsten Clay
Menke et al. recently claimed that superconductivity (SC) in the $ \kappa$ -phase organic charge-transfer solids (CTS) can be understood within the two-dimensional half-filled anisotropic triangular-lattice Hubbard model. Experimentally, $ \kappa$ -CTS are mostly but not always antiferromagnetic (AFM) at ambient pressure and SC appears under pressure. In apparent agreement with this observation, Menke et al. found AFM ground states for small $ t/U$ and SC over a small region at the interface of AFM and Fermi liquid ground states with increasing $ t/U$ at fixed $ t’/t$ , where $ U$ is the Hubbard repulsion. Menke et al’s computational results directly contradict those obtained using exact diagonalization and Path Integral Renormalization Group approaches. It is clearly of interest to determine the origin of this discrepancy, especially in view of the facts that (a) related arguments continue to persist in the context of cuprate SC superconductivity (which however involves doping), and (b) there exist CTS in which SC is not proximate to AFM, but is separated by an intermediate charge-disproportionated phase. Here we show that Menke et al’s conclusion regarding SC is incorrect and originates from a flawed assumption.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
Comment on arXiv:2401.10650 (Phys. Rev. Lett. 133, 136501 (2024); DOI https://doi.org/10.1103/PhysRevLett.133.136501). 2 pages, 1 figure