CMP Journal 2025-03-03
Statistics
Nature: 1
Nature Materials: 2
Nature Nanotechnology: 1
arXiv: 72
Nature
Constitutively active glucagon receptor drives high blood glucose in birds
Original Paper | Animal physiology | 2025-03-02 19:00 EST
Chang Zhang, Xiangying Xiang, Jian Liu, Yongjie Huang, Jingwen Xue, Qian Sun, Song Leng, Shaobo Liu, Xuefei He, Peng Hu, Xiangjiang Zhan, Qiang Qiu, Shilong Yang, Jürgen Brosius, Cheng Deng
As the body’s primary source of energy, the maintenance of blood glucose is indispensable for overall health and metabolic homeostasis. It is predominantly regulated by the glucagon receptor family which is highly conserved in vertebrates1-4. Compared to other vertebrates, avian blood glucose levels are relatively high5,6, yet its regulatory mechanisms have remained obscure for more than a century. We show that high hepatic expression of the avian glucagon receptor (GCGR) in association with constitutively active Gs signaling was dependent upon the interaction of different domains. In vivo experiments focusing on the regulation of constitutively active GCGR expression in hepatic cells led to correspondingly high blood glucose, rapid hepatic lipid utilization and high metabolic rates via downstream signaling pathway activation in fish, reptiles, birds, and mammals. Furthermore, we identified a point mutation in chicken at the proximal gene region that resulted in GCGR mRNA reduction and weight increase. Overexpressing a natural human GCGR mutation (hsGCGRH339R) with modest constitutive activity in mice, demonstrated that high level expression of this variant augmented high blood glucose, while reducing body weight. The combination of high expression and constitutive activity of the glucagon receptor may have contributed to the evolution of flight in the ancestors of birds.
Animal physiology, Molecular evolution
Nature Materials
Frozen non-equilibrium dynamics of exciton Mott insulators in moiré superlattices
Original Paper | Condensed-matter physics | 2025-03-02 19:00 EST
Shibin Deng, Heonjoon Park, Jonas Reimann, Jonas M. Peterson, Daria D. Blach, Meng-Jia Sun, Tengfei Yan, Dewei Sun, Takashi Taniguchi, Kenji Watanabe, Xiaodong Xu, Dante M. Kennes, Libai Huang
Moiré superlattices, such as those formed from transition metal dichalcogenide heterostructures, have emerged as an exciting platform for exploring quantum many-body physics. They have the potential to serve as solid-state analogues to ultracold gases for quantum simulations. A key open question is the coherence and dynamics of the quantum phases arising from photoexcited moiré excitons, particularly amid dissipation. Here we use transient photoluminescence and ultrafast reflectance microscopy to image non-equilibrium exciton phase transitions. Counterintuitively, experimental results and theoretical simulations indicate that strong long-range dipolar repulsion freezes the motion of the Mott insulator phase for over 70 ns. In mixed electron-exciton lattices, reduced dipolar interactions lead to diminished freezing dynamics. These findings challenge the prevailing notion that repulsion disperses particles, whereas attraction binds them. The observed phenomenon of frozen dynamics due to strong repulsive interactions is characteristic of highly coherent systems, a feature previously realized exclusively in ultracold gases.
Condensed-matter physics, Nanoscale materials
Microscopic crystallographic analysis of dislocations in molecular crystals
Original Paper | Organic molecules in materials science | 2025-03-02 19:00 EST
Sang T. Pham, Natalia Koniuch, Emily Wynne, Andy Brown, Sean M. Collins
Organic molecular crystals encompass a vast range of materials from pharmaceuticals to organic optoelectronics, proteins and waxes in biological and industrial settings. Crystal defects from grain boundaries to dislocations are known to play key roles in mechanisms of growth1,2 and in the functional properties of molecular crystals3,4,5. In contrast to the precise analysis of individual defects in metals, ceramics and inorganic semiconductors enabled by electron microscopy, substantially greater ambiguity remains in the experimental determination of individual dislocation character and slip systems in molecular materials3. In large part, nanoscale dislocation analysis in molecular crystals has been hindered by the low electron doses required to avoid irreversibly degrading these crystals6. Here we present a low-dose, single-exposure approach enabling nanometre-resolved analysis of individual dislocations in molecular crystals. We demonstrate the approach for a range of crystal types to reveal dislocation character and operative slip systems unambiguously.
Organic molecules in materials science, Structure of solids and liquids, Transmission electron microscopy
Nature Nanotechnology
Nanometre-resolution three-dimensional tomographic and vectorial near-field imaging in dielectric optical resonators
Original Paper | Metamaterials | 2025-03-02 19:00 EST
Bingbing Zhu, Qingnan Cai, Yaxin Liu, Sheng Zhang, Weifeng Liu, Qiong He, Lei Zhou, Zhensheng Tao
All-dielectric optical nano-resonators have emerged as low-loss, versatile and highly adaptable components in nanophotonic structures for manipulating electromagnetic waves and enhancing light-matter interactions. However, achieving full three-dimensional characterization of near fields within dielectric nano-resonators poses great experimental challenges. Here we develop a technique to image near-field wave patterns inside dielectric optical nano-resonators using high-order sideband generation. By exploiting the phase sensitivity of various harmonic orders, which enables the detection of near-field distributions at distinct depths, we achieve three-dimensional tomographic and near-field imaging with a transverse resolution of ~920 nm and a longitudinal resolution of ~130 nm inside a micrometre-thick silicon anapole resonator. Our method offers high-contrast polarization sensitivity and phase-resolving capabilities, providing comprehensive vectorial near-field information and could be applied to diverse dielectric metamaterials.
Metamaterials, Nanophotonics and plasmonics
arXiv
Noise induced extreme events in single Fitzhugh-Nagumo oscillator
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-03 20:00 EST
S. Hariharan, R. Suresh, V. K. Chandrasekar
The FitzHugh-Nagumo (FHN) model serves as a fundamental neuronal model which is extensively studied across various dynamical scenarios, we explore the dynamics of a scalar FHN oscillator under the influence of white noise. Unlike previous studies, in which extreme events (EE) were observed solely in coupled FHN oscillators, we demonstrate that a single system can exhibit EE induced by noise. Perturbation of the deterministic model in its steady state by random fluctuations reveals the emergence of subthreshold/small-amplitude oscillations (SAO), eventually leading to rare and extreme large-amplitude oscillations (LAO), which become particularly evident at minimal noise intensities. We elucidate the route by which these EE emerge, confirming their occurrence through probability calculations of trajectories in phase space. Additionally, our investigation reveals bursting phenomena in the system, which are characterized by specific levels of noise amplitude and elucidated using inter-spike interval statistics. At higher noise amplitudes, frequent LAO production is observed and attributed to self-induced stochastic resonance. The emergence of EE is explained through the theory of large fluctuations, with the escape rates of trajectories estimated via both analytical and numerical approaches. This study is significant because it reveals EE and bursting phenomena in a single FHN oscillator, offering potential new insights into the dynamics of neuronal populations.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Chaotic Dynamics (nlin.CD), Neurons and Cognition (q-bio.NC)
Accepted for publication in Chaos Solitons Fractals
Duality viewpoint of noninvertible symmetry protected topological phases
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Weiguang Cao, Masahito Yamazaki, Linhao Li
Recent advancements in generalized symmetries have drawn significant attention to gapped phases of matter exhibiting novel symmetries, such as noninvertible symmetries. By leveraging the duality transformations, the classification and construction of gapped phases with noninvertible symmetry can be mapped to those involving conventional group symmetries. We demonstrate this approach by classifying symmetry-protected topological phases with a broad class of noninvertible symmetries in arbitrary spacetime dimensions. Our results reveal new classifications that extend beyond those based on group symmetries. Additionally, we construct lattice models in $(1+1)d$ and $(2+1)d$ that realize these new phases and explore their anomalous interfaces.
Strongly Correlated Electrons (cond-mat.str-el), High Energy Physics - Theory (hep-th)
5+11 pages, 3 figures, 1 table
Universal electronic structure of layered nickelates via oxygen-centered planar orbitals
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Christine C. Au-Yeung, X. Chen, S. Smit, M. Bluschke, V. Zimmermann, M. Michiardi, P. Moen, J. Kraan, C. S. B. Pang, C. T. Suen, S. Zhdanovich, M. Zonno, S. Gorovikov, Y. Liu, G. Levy, I. S. Elfimov, M. Berciu, G. A. Sawatzky, J. F. Mitchell, A. Damascelli
Superconductivity has recently been demonstrated in La$_3$Ni$_2$O$_7$ up to 91K under moderate pressure in bulk crystals, and up to 48K at ambient pressure in thin films grown under compressive strain. Key questions remain open regarding the crystal structure and low-energy electronic states that support superconductivity in these compounds. Here we take advantage of the natural polymorphism between bilayer (2222) or alternating monolayer-trilayer (1313) stacking sequences that arises in bulk La$_3$Ni$2$O$7$ crystals to identify universal features in this family of materials. Employing angle-resolved photoemission spectroscopy (ARPES) we observe the fingerprint of a spin-density wave (SDW) instability, strong and coherent enough to modify the electronic structure. We demonstrate that this feature is a `translated’ $\beta$ Fermi surface associated with a scattering vector $Q{t\beta}$ which matches the $Q{SDW}$ detected by neutron and x-ray scattering experiments. This observation provides an important link between surface and bulk probes, and demonstrates a universal connection between magnetism and fermiology in La$_3$Ni$2$O$7$ as well as La$4$Ni$3$O${10}$. We simulate the spectral weight distribution observed in our ARPES dichroism experiments and establish that the low-energy electronic phenomenology is dominated by oxygen-centered planar orbitals, which – upon moving along the Fermi surface away from the Ni-O-Ni bond directions – evolve from the $d{3x^2-r^2}$ and $d{3y^2-r^2}$ symmetry characteristic of 3-spin polarons to the familiar $d{x^2-y^2}$ Zhang-Rice singlets that support high-temperature superconductivity in cuprates. Despite the multiorbital nature of the nickelates, our work establishes an empirical correspondence between the low-energy electronic structure of cuprates and nickelates, thus suggesting a common origin for their unconventional superconductivity.
Superconductivity (cond-mat.supr-con)
13 pages, 4 figures
Direct Observation of Massless Excitons and Linear Exciton Dispersion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Luna Y. Liu, Steffi Y. Woo, Jinyuan Wu, Bowen Hou, Cong Su, Diana Y. Qiu
Excitons – elementary excitations formed by bound electron-hole pairs – govern the optical properties and excited-state dynamics of materials. In two-dimensions (2D), excitons are theoretically predicted to have a linear energy-momentum relation with a non-analytic discontinuity in the long wavelength limit, mimicking the dispersion of a photon. This results in an exciton that behaves like a massless particle, despite the fact that it is a composite boson composed of massive constituents. However, experimental observation of massless excitons has remained elusive. In this work, we unambiguously experimentally observe the predicted linear exciton dispersion in freestanding monolayer hexagonal boron nitride (hBN) using momentum-resolved electron energy-loss spectroscopy. The experimental result is in excellent agreement with our theoretical prediction based on ab initio many-body perturbation theory. Additionally, we identify the lowest dipole-allowed transition in monolayer hBN to be at 6.6 eV, illuminating a long-standing debate about the band gap of monolayer hBN. These findings provide critical insights into 2D excitonic physics and open new avenues for exciton-mediated superconductivity, Bose-Einstein condensation, and high-efficiency optoelectronic applications.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph)
Axion electrodynamics and giant magnetic birefringence in Weyl excitonic insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Anna Grigoreva, Anton Andreev, Leonid Glazman
We study electromagnetic (EM) response of the excitonic insulator phase of time-reversal invariant Weyl semimetals (WSMs). Because of the chiral anomaly and the chiral magnetic effect in the parent WSM, the phase of the exciton condensate couples to the EM fields as a massive dynamical axion. Although the translational symmetry of the WSM is broken in the excitonic insulator state, the axion field is not related to the phase of the sliding exciton density wave. The axion mass is generated by the inter-band matrix elements of electron-electron interactions, and is much smaller than the gap in the single-particle spectrum. Due to the small axion mass, in the presence of a magnetic field, the axion coupling to EM fields produces giant anisotropic polarizability and birefringence. The photon-axion hybridization produces a polariton resonance near the axion gap.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 pages, 1 figure
Plasmonic waveguides in two-dimensional materials: a quantum mechanical description using semiclassical techniques
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
T. M. Koskamp, M. I. Katsnelson, K. J. A. Reijnders
Plasmons are likely to play an important role in integrated photonic ciruits, because they strongly interact with light and can be confined to subwavelength scales. These plasmons can be guided and controlled by plasmonic waveguides, which can be created by patterning different materials or by structuring the dielectric environment. We have constructed a semi-analytical theory to describe plasmonic waveguides, and, more generally, plasmons in spatially inhomogeneous systems. Our theory employs techniques from semiclassical analysis, and is therefore applicable when the electron wavelength is much smaller than the characteristic length scale of changes in the system parameters. We obtain an effective classical Hamiltonian that describes the dynamics of quantum plasmons, given by the Lindhard function with spatially varying parameters. Adding the wave-like character of the plasmons to the classical trajectories generated by this Hamiltonian, we find two different mechanisms for waveguiding. In the first case, a localized plasmonic state arises due to total internal reflection similar to photonic waveguides. The second mechanism relies on a varying dielectric environment, which locally modifies the screening of the electrons. Here, a quasi-localized state arises due to local changes in the amplitude of the plasmonic excitation. Our results provide a solid basis to understand previous numerical studies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Optics (physics.optics)
26 pages, 10 figures
Viscoelastic tensor and hydrodynamics of altermagnets
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
A. A. Herasymchuk, E. V. Gorbar, P. O. Sukhachov
We calculate the viscoelasticity tensor for altermagnets and formulate the corresponding hydrodynamic equations. The anisotropy of altermagnetic Fermi surfaces allows for additional terms in the viscoelasticity tensor and is manifested in transport properties including electron and spin flows in a channel and nonlocal responses. In the channel geometry, the altermagnetic spin splitting leads to nontrivial spin density and spin current. Like the electric current, the spin current acquires a Poiseuille profile for no-slip boundary conditions. In nonlocal responses, the altermagnetic anisotropy affects current streamlines and electric potential distributions in the viscous regime. Our results provide signatures of the hydrodynamic transport regime in altermagnets potentially facilitating its experimental studies and discovery.
Strongly Correlated Electrons (cond-mat.str-el), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
15 pages, 4 figures
Universal Anyon Tunneling in a Chiral Luttinger Liquid
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Ramon Guerrero-Suarez, Adithya Suresh, Tanmay Maiti, Shuang Liang, James Nakamura, Geoffrey Gardner, Claudio Chamon, Michael Manfra
The edge modes of fractional quantum Hall liquids are described by chiral Luttinger liquid theory. Despite many years of experimental investigation fractional quantum Hall edge modes remain enigmatic with significant discrepancies between experimental observations and detailed predictions of chiral Luttinger liquid theory. Here we report measurements of tunneling conductance between counterpropagating edge modes at $\nu=1/3$ across a quantum point contact fabricated on an AlGaAs/GaAs heterostructure designed to promote a sharp confinement potential. We present evidence for tunneling of anyons through an $\nu=1/3$ incompressible liquid that exhibits universal scaling behavior with respect to temperature, source-drain bias, and barrier transmission, as originally proposed by Wen[1,2]. We measure the tunneling exponent $g = 0.334 \pm 0.001$, consistent with the scaling dimension $\Delta = g/2 = 1/6$ for a Laughlin quasiparticle at the edge. When combined with measurements of the fractional charge $e^\ast=e/3$ and the recently observed anyonic statistical angle $\theta_a=\frac{2\pi}{3}$, the measured tunneling exponent fully characterizes the topological order of the primary Laughlin state at $\nu=1/3$.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
9 pages, 4 figures
Mean-field approximation and phase transitions in an Ising-voter model on directed regular random graphs
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
Adam Lipowski, Antonio Luis Ferreira, Dorota Lipowska, Aleksandra Napierala-Batygolska
It is known that on directed graphs, the correlations between neighbours of a given site vanish and thus simple mean-field-like arguments can be used to describe exactly the behaviour of Ising-like systems. We analyse heterogeneous modifications of such models where a fraction of agents is driven by the voter or the antivoter dynamics. It turns out that voter agents do not affect the dynamics of the model and it behaves like a pure Ising model. Antivoter agents have a stronger impact since they act as a kind of noise, which weakens a ferromagnetic ordering. Only when Ising spins are driven by the heat-bath dynamics, the behaviour of the model is correctly described by the mean-field approximation. The Metropolis dynamics generates some additional correlations that render the mean-field approach approximate. Simulations on annealed networks agree with the mean-field approximation but for the model with antivoters and with the Metropolis dynamics only its heterogeneous version provides such an agreement. Calculation of the Binder cumulant confirms that critical points in our models with the heat-bath dynamics belong to the Ising mean-field universality class. For the Metropolis dynamics, the phase transition is most likely discontinuous, at least for not too many antivoters.
Statistical Mechanics (cond-mat.stat-mech)
11 pages
Phys. Rev. E 111, 024317 (2025)
Formation of Frustrated Charge Density Waves in Kagome Metal LuNb$_6$Sn$_6$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
F. Z. Yang, X. Huang, Hengxin Tan, A. Kundu, S. Kim, M. Thinel, J. Ingham, A. Rajapitamahuni, C. Nelson, Y. Q. Cai, E. Vescovo, W. R. Meier, D. Mandrus, Brenden R. Ortiz, A. N. Pasupathy, Binghai Yan, H. Miao
The charge density wave (CDW), a translational symmetry breaking electronic liquid, plays a pivotal role in correlated quantum materials, such as high-T$_c$ superconductors and topological semimetals. Recently, CDWs that possibly intertwine with superconductivity and magnetism are observed in various kagome metals. However, the nature of CDWs and the role of the Fermi surface (FS) topology in these materials remain an unresolved challenge. In this letter, we reveal the formation of CDWs in the newly discovered kagome metal LuNb$_6$Sn$6$. We observe a precursor CDW correlation that features a “yield sign”-like hollow triangle diffuse scattering pattern and nearly complete softening of a flat optical phonon band near Q$H$=(1/3, 1/3, 1/2). The scattering intensity of the precursor CDW displays divergent behavior as decreasing temperature until T${CDW}$=70 K, where a competing CDW at Q${CDW}$=(1/3, 1/3, 1/3) emerges. Using scanning tunneling microscopy/spectroscopy, we image the frustrated CDW patterns that show a short phase coherence length about ~20 nm in real space. Combined with first principles calculations, our observations support frustrated lattice interactions that are modulated by the FS topology. These results shed light on the interplay between FS and CDW in quantum materials with nearly degenerate structural deformation patterns.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Orbital-excitation-dominated magnetization dissipation and quantum oscillation of Gilbert damping in Fe films
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Yue Chen, Haoran Chen, Xi Shen, Weizhao Chen, Yi Liu, Yizheng Wu, Zhe Yuan
Using first-principles electronic structure calculation, we demonstrate the spin dissipation process in bulk Fe by orbital excitations within the energy bands of pure spin character. The variation of orbitals in the intraband transitions provides an efficient channel to convert spin to orbital angular momentum with spin-orbit interaction. This mechanism dominates the Gilbert damping of Fe below room temperature. The theoretical prediction is confirmed by the ferromagnetic resonance experiment performed on single-crystal Fe(001) films. A significant thickness-dependent damping oscillation is found at low temperature induced by the quantum well states of the corresponding energy bands. Our findings not only explain the microscopic nature of the recently reported ultralow damping of Fe-based alloys, but also help for the understanding of the transport and dissipation process of orbital currents.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci)
Order parameter fluctuation effects on current-induced magnetization
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Genta Furuya, Kazumasa Hattori
We investigate the impact of order parameter fluctuations on magnetoelectric effects in metallic systems using classical Monte Carlo simulations. We focus on a a chiral quadrupole order in a distorted kagome lattice in a model incorporating conduction electrons and classical orbital moments. The ordered orbital moments break mirror symmetry and couple with the conduction electrons, leading to a current-induced magnetization driven by the quadrupole order. Our findings reveal that order parameter fluctuations significantly affect the current-induced magnetization, strongly suppressing the response over a broad temperature range below the transition temperature. Additionally, we analyze the influence of Fermi surface properties and associated matrix elements on this phenomenon. Our results highlight the crucial role of fluctuation effects, demonstrating a qualitatively distinct temperature dependence of the current-induced magnetization compared to that of the order parameter itself.
Strongly Correlated Electrons (cond-mat.str-el)
9 pages and 8 figures
Lattice Protein Folding with Variational Annealing
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-03 20:00 EST
Shoummo Ahsan Khandoker, Estelle M. Inack, Mohamed Hibat-Allah
Understanding the principles of protein folding is a cornerstone of computational biology, with implications for drug design, bioengineering, and the understanding of fundamental biological processes. Lattice protein folding models offer a simplified yet powerful framework for studying the complexities of protein folding, enabling the exploration of energetically optimal folds under constrained conditions. However, finding these optimal folds is a computationally challenging combinatorial optimization problem. In this work, we introduce a novel upper-bound training scheme that employs masking to identify the lowest-energy folds in two-dimensional Hydrophobic-Polar (HP) lattice protein folding. By leveraging Dilated Recurrent Neural Networks (RNNs) integrated with an annealing process driven by temperature-like fluctuations, our method accurately predicts optimal folds for benchmark systems of up to 60 beads. Our approach also effectively masks invalid folds from being sampled without compromising the autoregressive sampling properties of RNNs. This scheme is generalizable to three spatial dimensions and can be extended to lattice protein models with larger alphabets. Our findings emphasize the potential of advanced machine learning techniques in tackling complex protein folding problems and a broader class of constrained combinatorial optimization challenges.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Artificial Intelligence (cs.AI), Machine Learning (cs.LG), Biomolecules (q-bio.BM)
Github respository will be provided soon
Eightfold Degenerate Dirac Nodal Line in Collinear Antiferromagnet Mn$_5$Si$_3$
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Victor Mendoza-Estrada, Rafael González-Hernández, Bernardo Uribe, Libor Šmejkal
We study the electronic, magnetic, and spin transport properties of the orthorhombic Mn${5}$Si${3}$ compound in the $AF2$ phase using symmetry analysis and ab-initio calculations. Our ground state energy calculations align with experimental observations, demonstrating that the collinear antiferromagnetic (AFM) order, with Néel vector in the [010] direction, is the most stable magnetic configuration both with and without spin-orbit coupling (SOC) in a bulk lattice geometry. We identified an unconventional eight-fold degenerate Dirac nodal line (DNL) close to the Fermi level, characterized by negligible SOC. This DNL is robustly protected by a unique combination of a pure-spin symmetry and a lattice symmetry together with magnetic space group symmetries. Upon introducing SOC, this degeneracy is reduced to two four-fold DNLs, being protected by the combination of time-reversal, partial translation and nonsymmorphic symmetries within the magnetic space group. We predict also a large intrinsic spin Hall conductivity (SHC) which correlates with the presence of SOC-induced splitting of these eight-fold degenerate DNLs near the Fermi level. These intriguing characteristics position collinear antiferromagnet Mn${5}$Si${3}$ as a compelling candidate for spintronic applications, particularly in the generation and detection of spin currents, while remaining compatible with modern silicon technology.
Materials Science (cond-mat.mtrl-sci), Algebraic Topology (math.AT)
14 pages, 3 figures
Phys. Rev. B 111, 085147 (2025)
Gravity-induced Diffusivity of an Axisymmetric Brownian Particle
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
Zhongqiang Xiong, Ryohei Seto, Masao Doi
A rigid axisymmetric particle with hydrodynamic anisotropy exhibits gliding motion in a quiescent Newtonian fluid under gravity. When Brownian motion is significant, the orientation of the particle fluctuates during sedimentation. We perform an analytical calculation for this sedimentation process. Our results show that gravity can significantly enhance the spatial diffusion of the particle. In addition to Brownian diffusion, gravity induces an additional apparent diffusivity. This gravity-induced diffusivity increases quadratically with the sedimentation Péclet number in the high Péclet number regime and is further enhanced by hydrodynamic anisotropy when the particle shape deviates from a sphere at a fixed Péclet number. When the centers of mass and buoyancy deviate from the hydrodynamic center, the particle tends to align with the direction of gravity. This alignment reduces the effective translational resistance along the gravity direction, thereby increasing the sedimentation velocity. At a given Péclet number, the horizontal diffusivity exhibits a peak before converging to the normal diffusion constant as the center deviation becomes larger.
Statistical Mechanics (cond-mat.stat-mech)
Polar Vortex Superstructure and Its Coupling with Correlated Electrons in Quasiperiodic Moire Crystal
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Si-yu Li, Zhongrui Wang, Yingzhuo Han, Shaoqing Xu, Zhiyue Xu, Yingbo Wang, Zhengwen Wang, Yucheng Xue, Aisheng Song, Kenji Watanabe, Takashi Taniguchi, Xueyun Wang, Tian-Bao Ma, Jiawang Hong, Hong-Jun Gao, Yuhang Jiang, Jinhai Mao
Nanoscale polar structures are significant for understanding polarization processes in low-dimensional systems and hold potential for developing high-performance electronics. Here, we demonstrate a polar vortex superstructure arising from the reconstructed moiré patterns in twisted bilayer graphene aligned with hexagonal boron nitride. Scanning tunneling microscopy reveals spatially modulated charge polarization, while theoretical simulations indicate that the in-plane polarization field forms an array of polar vortices. Notably, this polar field is gate-tunable, exhibiting an unconventional gate-tunable polar sliding and screening process. Moreover, its interaction with electron correlations in twisted bilayer graphene leads to modulated correlated states. Our findings establish moiré pattern reconstruction as a powerful strategy for engineering nanoscale polar structures and emergent quantum phases in van der Waals materials.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
4 Figures
Finite-momentum dielectric function and excitonic effects from time-dependent density-functional theory with dielectrically screened hybrid functionals
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Didarul Alam, Jiuyu Sun, Carsten A. Ullrich
This paper studies the performance of time-dependent density-functional theory (TDDFT) for calculating the dielectric function of semiconductors and insulators at finite momentum transfer, comparing against the standard Bethe-Salpeter equation (BSE). Specifically, we consider a recently proposed hybrid approach that mixes dielectrically screened exact exchange with a semilocal functional, and we also introduce a new hybrid functional featuring a truncated dielectric screening scheme. The computational effort of these hybrid TDDFT approaches is significantly less than that of the BSE, but they deliver comparable accuracy, as demonstrated for the semiconductors Si and GaN and the wide-band insulator LiF. This opens up possibilities for calculating exciton dispersions and electron energy loss functions efficiently and accurately for a wide range of materials.
Materials Science (cond-mat.mtrl-sci)
12 pages, 6 figures
First passage time properties of diffusion with a broad class of stochastic diffusion coefficients
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
Go Uchida, Hiromi Miyoshi, Hitoshi Washizu
Diffusion in a heterogeneous environment or diffusion of a particle that shows conformational fluctuations can be described by Brownian motions with stochastic diffusion coefficients (DCs). In the present study, we investigate first passage time (FPT) properties of diffusion with a broad class of stochastic DCs that are positive and non-zero. We show that for diffusion in one-dimensional semi-infinite domain with an absorbing boundary, the eventual absorption is certain. We also show that compared to diffusion whose DC is the ensemble average of a stochastic DC, in diffusion with the stochastic DC, there are particles that reach the absorbing boundary earlier. The approximate proportion of preceding particles is determined by the probability distribution of the time average of a stochastic DC for a given distance to the absorbing boundary. In addition, when particles begin to reach the absorbing boundary before the time change in a stochastic DC occurs, a stochastic DC with a larger supremum leads to an earlier arrival of particles at the absorbing boundary even if the ensemble averages of stochastic DCs are the same. For ergodic DCs, three more properties are revealed. The mean FPT is infinite. In addition, if particles take a long time to reach the absorbing boundary, the exact proportion of preceding particles is almost zero and the FPT distribution can be approximated by the Lévy-Smirnov distribution. We show that these three properties of diffusion with an ergodic DC result from the convergence of the time average of the DC to the ensemble average. For three-dimensional diffusion with a spherical absorbing boundary, we obtain essentially the same results, except that the eventual absorption is not certain. Our results suggest that fluctuations in a DC play an important role in diffusion-limited reactions triggered by single molecules in physics, chemistry, or biology.
Statistical Mechanics (cond-mat.stat-mech), Biological Physics (physics.bio-ph)
10 pages, 4 figures
Causal horizon from quantum fluctuations
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
We propose a simple model of quantum void where the flow of time is deduced directly from quantum fluctuations and the consequent particle-antiparticle creations. Given a certain number of space-like separated pair creation events, assumed to happen all at the same initial time, we show that past and future can be foliated into a sequence of adapted manifolds based on how many events causally influence them. We also give an explicit construction for the simplest case of one space dimension.
Statistical Mechanics (cond-mat.stat-mech), General Relativity and Quantum Cosmology (gr-qc)
9 pages, 6 figures
Melting Points and Formation Free Energies of Carbon Compounds with Sodalite Structure
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Using first-principles calculations, we investigate the melting temperatures $T_{\rm m}$ and formation free energy of carbon compounds with sodalite structures, $X$C$ 6$, $X$C$ {10}$, and $X$C$ {12}$, where $X$ is F, Na, Cl, and so on. These compounds are expected to be phonon-mediated superconductors exhibiting high transition temperatures $T{\rm c}$ of up to about 100 K. We estimate $T{\rm m}$ as a function of pressure $P$ by using the first-principles molecular dynamics method and show the results as phase diagrams on the $P$-$T$ plane together with the results of $T{\rm c}$. It indicates that the $T_{\rm m}$ of NaC${\rm 6}$, which has a $T{\rm c}$ up to about 100 K, is about $1300$ K or more at $P=30$ GPa. Furthermore, the $T_{\rm m}$ of FC${\rm 6}$ is about 2200 K even at $P=0$ GPa, where its $T{\rm c}$ is about 80 K. Similar results are obtained for FC${\rm 10}$ and ClC${\rm 10}$ systems. These results suggest that some compounds can stably exist as high-temperature superconductors even at room temperature and pressure. To examine the feasibility of synthesizing these compounds, we estimate the formation enthalpies and formation free energies. These results suggest that NaC$_6$ could be formed under a sufficiently high pressure of about 300 GPa and a high temperature of about 6500 K.
Materials Science (cond-mat.mtrl-sci), Superconductivity (cond-mat.supr-con)
10 pages, 13 figures
Symmetry-Broken Kondo Screening and Zero-Energy Mode in the Kagome Superconductor CsV3Sb5
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Yubing Tu, Zongyuan Zhang, Wenjian Lu, Tao Han, Run Lv, Zhuying Wang, Zekun Zhou, Xinyuan Hou, Ning Hao, Zhenyu Wang, Xianhui Chen, Lei Shan
The quantum states of matter reorganize themselves in response to defects, giving rise to emergent local excitations that imprint unique characteristics of the host states. While magnetic impurities are known to generate Kondo screening in a Fermi liquid and Yu-Shiba-Rusinov (YSR) states in a conventional superconductor, it remains unclear whether they can evoke distinct phenomena in the kagome superconductor AV3Sb5 (where A is K, Rb or Cs), which may host an orbital-antiferromagnetic charge density wave (CDW) state and an unconventional superconducting state driven by the convergence of topology, geometric frustration and electron correlations. In this work, we visualize the local density of states induced near various types of impurities in both the CDW and superconducting phases of CsV3-xMxSb5 (M = Ta, Cr) using scanning tunneling microscopy. We observe Kondo resonance states near magnetic Cr dopants. Notably, unlike in any known metal or CDW compound, the spatial pattern of Kondo screening breaks all in-plane mirror symmetries of the kagome lattice, suggesting an electronic chirality due to putative orbital loop currents. While Cooper pairs show relative insensitivity to nonmagnetic impurities, native V vacancies with weak magnetic moments induce a pronounced zero-bias conductance peak (ZBCP). This ZBCP coexists with trivial YSR states within the superconducting gap and does not split in energy with increasing tunneling transmission, tending instead to saturate. This behavior is reminiscent of signature of Majorana zero modes, which could be trapped by a sign-change boundary in the superconducting order parameter near a V vacancy, consistent with a surface topological superconducting state. Our findings provide a new approach to exploring novel quantum states on kagome lattices.
Superconductivity (cond-mat.supr-con), Strongly Correlated Electrons (cond-mat.str-el)
19 pages, 4 figures
Spatially anisotropic Kondo resonance intertwined with superconducting gap in kagome metal CsV3-xCrxSb5
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Zichen Huang, Hui Chen, Zhongqin Zhang, Hao Zhang, Zhen Zhao, Ruwen Wang, Haitao Yang, Wei Ji, Ziqiang Wang, Hong-Jun Gao
The newly-discovered chromium-based kagome metal CsCr3Sb5 has garnered significant interest due to its strong electron correlations, intertwined orders and potential for unconventional superconductivity under high pressure. However, the nature of superconducting and magnetic interactions during the transition from the parent compound CsV3Sb5 to CsCr3Sb5 remains elusive. Here, we report the discovery of spatially anisotropic Kondo resonance which intertwines with the superconducting gap, facilitated by the introduction of magnetic Cr impurities into the kagome superconductor CsV3Sb5. In addition to the gradual suppression of long-ranged charge-density-wave orders, dilute Cr dopants induce local magnetic moments, giving rise to the emergence of Kondo resonances. In addition, the Kondo resonance forms spatially anisotropic ripple-like structures around the Cr dopants, breaking all local mirror symmetries. This anisotropy arises from the antiferromagnetic coupling between itinerant electrons and the Cr-induced spin-up electrons. Remarkably, as the Kondo screening develops, the coherence peak and depth of superconducting gap with finite zero-energy conductance significantly enhances. It indicates that non-superconducting pairs at the Fermi surface in the parent compound participate in the Kondo effect, effectively screening the magnetic moments of Cr dopants while simultaneously enhancing the superfluid density. Our findings pave a unique pathway for exploring the interplay between superconductivity and local magnetic moments in kagome systems.
Superconductivity (cond-mat.supr-con)
Twisted oxide membrane interface by local atomic registry design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Min-Su Kim, Kyoungjun Lee, Ryo Ishikawa, Kyung Song, Naafis Ahnaf Shahed, Ki-Tae Eom, Mark S. Rzchowski, Evgeny Y. Tsymbal, Naoya Shibata, Teruyasu Mizoguchi, Chang-Beom Eom, Si-Young Choi
Interplay of lattice, orbital, and charge degrees of freedom in complex oxide materials has hosted a plethora of exotic quantum phases and physical properties. Recent advances in synthesis of freestanding complex oxide membranes and twisted heterostructures assembled from membranes provide new opportunities for discovery using moiré design with local lattice control. To this end, we designed moiré crystals at the coincidence site lattice condition, providing commensurate structure within the moiré supercell arising from the multi-atom complex oxide unit cell. We fabricated such twisted bilayers from freestanding SrTiO3 membranes and used depth sectioning-based TEM methods to discover ordered charge states at the moiré interface. By selectively imaging SrTiO3 atomic planes at different depths through the bilayer, we clearly resolved the moiré periodic structure at the twisted interface and found that it exhibits lattice-dependent charge disproportionation in the local atomic registry within the moiré supercell. Our density-functional modelling of the twisted oxide interface predicts that these moiré phenomena are accompanied by the emergence of a two-dimensional flat band that can drive new electronic phases. Our work provides a novel guideline for controlling moiré periodicity in twisted oxides and opens pathways to exploit the new functionalities via moiré lattice-driven charge-orbital correlation.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
22 pages, 4 figures
Thermally driven two-sphere microswimmer with internal feedback control
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Jun Li, Ziluo Zhang, Zhanglin Hou, Yuto Hosaka, Kento Yasuda, Linli He, Shigeyuki Komura
We discuss the locomotion of a thermally driven elastic two-sphere microswimmer with internal feedback control that is realized by the position-dependent friction coefficients. In our model, the two spheres are in equilibrium with independent heat baths having different temperatures, causing a heat flow between the two spheres. We generally show that the average velocity of the microswimmer is nonzero when the friction coefficients are position-dependent. Using the method of stochastic thermodynamics, we obtain the entropy production rate and discuss the efficiency of the two-sphere microswimmer. The proposed self-propulsion mechanism highlights the importance of information in active matter and can be a fundamental process in various biological systems.
Soft Condensed Matter (cond-mat.soft)
Efimov Effect in Long-range Quantum Spin Chains
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-03 20:00 EST
Ning Sun, Lei Feng, Pengfei Zhang
When two non-relativistic particles interact resonantly in three dimensions, an infinite tower of three-body bound states emerges, exhibiting a discrete scale invariance. This universal phenomenon, known as the Efimov effect, has garnered extensive attention across various fields, including atomic, nuclear, condensed matter, and particle physics. In this letter, we demonstrate that the Efimov effect also manifests in long-range quantum spin chains. The long-range coupling modifies the low-energy dispersion of magnons, enabling the emergence of continuous scale invariance for two-magnon states at resonance. This invariance is subsequently broken to discrete scale invariance upon imposing short-range boundary conditions for the three-magnon problem, leading to the celebrated Efimov bound states. Using effective field theory, we theoretically determine how the ratio of two successive binding energies depends on the interaction range, which agrees with the numerical solution of the bound-state problem. We further discuss generalizations to arbitrary spatial dimensions, where the traditional Efimov effect serves as a special case. Our results reveal universal physics in dilute quantum gases of magnons that can be experimentally tested in trapped-ion systems.
Quantum Gases (cond-mat.quant-gas), Quantum Physics (quant-ph)
7 pages, 3 figures + supplementary material
Enhanced Performance and Stability of Perovskite Solar Cells with Ag-Cu-Zn Alloy Electrodes
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Keshav Kumar Sharma, Ashutosh Ujjwal, Rohit Saini, Ramesh Karuppannan
Though the common metal electrode-based perovskite solar cells have achieved a power conversion efficiency of >25%, they also play a crucial role in accelerating the degradation of the cells. In this study, we investigated phase transition engineering in Ag electrodes via Cu and Zn alloying, transforming from a cubic to a tetragonal phase. These alloyed electrodes are then thermally deposited as back electrodes in perovskite solar cells. We conducted a comprehensive analysis of the pure Ag and Ag-Cu-Zn alloys deposited atop a hole-transport layer for use in Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3-based solar cells. Our findings reveal that solar cells developed with pure Ag electrodes demonstrate a power conversion efficiency (PCE) of 18.71%, characterized by a fill factor (FF) of 74.8%, an open-circuit voltage (VOC) of 1.08 V, and a short-circuit current density (JSC) of 23.17 mA/cm2. Conversely, solar cells fabricated with optimized Ag0.875Cu0.120Zn0.005 electrodes exhibit enhanced performance metrics, with an FF of 72.5%, VOC of 1.12 V, and JSC of 23.39 mA/cm2, culminating in an elevated PCE of 19.02%. Moreover, this electrode demonstrates remarkable durability, sustaining operational integrity for 460 hours for the PSCs stored in the N2 glove box, in contrast to the 320 hours for cells with Ag electrodes. The Ag-Cu-Zn alloys exhibited high resistance to corrosion and good adhesion on the hole-transport material layer compared to a layer of Ag. These advancements may lead to the realization of cost-effective, durable, and efficient solar energy conversion systems.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph)
25 pages, 22 figures
Unraveling the origin of Kondo-like behavior in the 3$d$-electron heavy-fermion compound YFe${2}$Ge${2}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Bing Xu, Rui Liu, Hongliang Wo, Zhiyu Liao, Shaohui Yi, Chunhong Li, Jun Zhao, Xianggang Qiu, Zhiping Yin, Christian Bernhard
The heavy fermion (HF) state of $d$-electron systems is of great current interest since it exhibits various exotic phases and phenomena that are reminiscent of the Kondo effect in $f$-electron HF systems. Here, we present a combined infrared spectroscopy and first-principles band structure calculation study of the $3d$-electron HF compound YFe$_2$Ge$_2$. The infrared response exhibits several charge-dynamical hallmarks of HF and a corresponding scaling behavior that resemble those of the $f$-electron HF systems. In particular, the low-temperature spectra reveal a dramatic narrowing of the Drude response along with the appearance of a hybridization gap ($\Delta \sim$ 50 meV) and a strongly enhanced quasiparticle effective mass. Moreover, the temperature dependence of the infrared response indicates a crossover around $T^{\ast} \sim$ 100 K from a coherent state at low temperature to a quasi-incoherent one at high temperature. Despite of these striking similarities, our band structure calculations suggest that the mechanism underlying the HF behavior in YFe$_2$Ge$_2$ is distinct from the Kondo scenario of the $f$-electron HF compounds and even from that of the $d$-electron iron-arsenide superconductor KFe$_2$As$_2$. For the latter, the HF state is driven by orbital-selective correlations due to a strong Hund’s coupling. Instead, for YFe$_2$Ge$_2$ the HF behavior originates from the band flatness near the Fermi level induced by the combined effects of kinetic frustration from a destructive interference between the direct Fe-Fe and indirect Fe-Ge-Fe hoppings, band hybridization involving Fe $3d$ and Y $4d$ electrons, and electron correlations. This highlights that rather different mechanisms can be at the heart of the HF state in $d$-electron systems.
Strongly Correlated Electrons (cond-mat.str-el), Superconductivity (cond-mat.supr-con)
11 pages, 7 figures
PNAS 121, e2401430121 (2024)
Spin waves in the bilayer van der Waals magnet CrSBr
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Rob den Teuling, Ritesh Das, Artem V. Bondarenko, Elena V. Tartakovskaya, Gerrit E. W. Bauer, Yaroslav M. Blanter
We derive analytical expressions for the spin wave frequencies and precession amplitudes in monolayer and antiferromagnetically coupled bilayer CrSBr under in-plane external magnetic fields. The analysis covers the antiferromagnetic, ferromagnetic, and canted phases, demonstrating that the spin wave frequencies in all phases are tunable by the applied magnetic field. We discuss the roles of intra- and interlayer exchange interactions, triaxial anisotropy, and intralayer dynamic dipolar fields in controlling the magnetization dynamics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
14 pages, 8 figures
PFD: Automatically Generating Machine Learning Force Fields from Universal Models
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Ruoyu Wang, Yuxiang Gao, Hongyu Wu, Zhicheng Zhong
Universal force fields generalizable across the periodic table represent a new trend in computational materials science. However, the applications of universal force fields in material simulations are limited by their slow inference speed and the lack of first-principles accuracy. Instead of building a single model simultaneously satisfying these characteristics, a strategy that quickly generates material-specific models from the universal model may be more feasible. Here, we propose a new workflow pattern, PFD, which automatically generates machine-learning force fields for specific materials from a pre-trained universal model through fine-tuning and distillation. By fine-tuning the pre-trained model, our PFD workflow generates force fields with first-principles accuracy while requiring one to two orders of magnitude less training data compared to traditional methods. The inference speed of the generated force field is further improved through distillation, meeting the requirements of large-scale molecular simulations. Comprehensive testing across diverse materials including complex systems such as amorphous carbon, interface, etc., reveals marked enhancements in training efficiency, which suggests the PFD workflow a practical and reliable approach for force field generation in computational material sciences.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
9 pages, 9 figures
Theory of Slidetronics in Ferroelectric van der Waals Layers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Byeoksong Lee, Minki Lee, Joongoo Kang
Vertically stacked layers derived from non-ferroelectric monolayers offer a promising route to two-dimensional (2D) ferroelectrics, where polarization switching occurs via interlayer sliding at sub-unit cell scales. Here, we develop a theory of slidetronics based on the notion that sliding-induced switching $P \rightarrow P’$ can also be achieved by applying an appropriate point-group operator $G$ to the entire system, such that $P’ = G P$. Interlayer sliding and the transformation induced by the generator $G$ are thus equivalent in describing the relationship between the initial and final layer configurations. From this symmetry principle, we deduce that slidetronics can be classified by generators $G$; the generator $G$ must act as a symmetry operator for the constituent layers, while it is not a symmetry operator for the stacked layers as a whole; for a given 2D material, $G$ determines the interlayer sliding required for polarization switching; and sliding-induced complete polarization inversion is impossible in bilayers but can be realized in multilayers (e.g., PdSe$_2$ trilayers). These findings provide a framework for designing 2D ferroelectrics with targeted polarization-switching properties, as demonstrated through case studies of real materials.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Effect of substrate temperature on the deposition of Al-doped ZnO thin films using high power impulse magnetron sputtering
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Martin Mickan (GREMI), Ulf Helmersson, David Horwat (IJL)
Al-doped ZnO thin films were deposited using reactive high power impulse magnetron sputtering at substrate temperatures between room temperature and 600 $\bullet$ C. Two sample series with different oxygen partial pressures were studied. The films with the lowest resistivity of 3 x 10 -4 $\Omega$cm were deposited at the highest substrate temperature of 600 $\bullet$ C. The improvement of the electrical properties could be related to an improvement of the mobility due to the improved crystallinity. This improved crystallinity also increased the stability of the films towards ambient moisture. On the other hand, the detrimental influence of negative oxygen bombardment could be avoided, as the HiPIMS process can take place in the metal or transition mode even at relatively high oxygen partial pressures.
Materials Science (cond-mat.mtrl-sci)
Surface and Coatings Technology, 2018, 347, pp.245-251
Cyanothiazole Copper(I) Complexes: Uncharted Materials with Exceptional Optical and Conductive Properties
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Karolina Gutmańska, Agnieszka Podborska, Tomasz Mazur, Andrzej Sławek, Ramesh Sivasamy, Alexey Maximenko, Łukasz Orzeł, Janusz Oszajca, Grażyna Stochel, Konrad Szaciłowski, Anna Dołęga
Cyanothiazoles, small and quite overlooked molecules, possess remarkable optical properties that can be fine-tuned through coordination with transition metals. In this study, we investigate a promising application of cyanothiazoles, where their combination with copper(I) iodide forms a new class of complexes exhibiting outstanding optical properties. X-ray crystallography of copper(I) iodide complexes with isomeric cyanothiazoles revealed key structural features, such as {\pi}-{\pi} stacking, hydrogen bonding, and rare halogen-chalcogen I-S interactions, enhancing stability and reactivity. Advanced spectroscopy and computational modeling allowed precise identification of spectral signatures in FTIR, NMR, and UV-Vis spectra. Fluorescence studies, along with XANES synchrotron analyses, highlighted their unique thermal and electronic properties, providing a solid foundation for further research in the field.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Structural Insights and Advanced Spectroscopic Characterization of Thiazolothiazoles: Unveiling Potential for Optoelectronic and Sensing Applications
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Karolina Gutmańska, Agnieszka Podborska, Andrzej Sławek, Ramesh Sivasamy, Lulu Alluhaibi, Alexey Maximenko, Anna Ordyszewska, Konrad Szaciłowski, Anna Dołęga, Tomasz Mazur
Thiazolothiazoles (TzTz) represent a class of compounds with distinctive structural motifs and exceptional optical properties, positioning them as promising candidates for breakthroughs in optoelectronic and sensing technologies. X-ray crystallographic analyses of TzTz units symmetrically substituted with functional groups such as imidazole, o-vanillin, p-vanillin, phenyl, thiazole, cinnamate, and bistrifluoromethylphenyl have revealed complex structural features, including {\pi}-{\pi} stacking interactions, hydrogen-bond networks, and specific chalcogen and halogen interactions. These interactions collectively enhance the stability and define the unique spectroscopic profiles of these compounds. Beyond classical spectral fingerprints (FTIR, NMR, and UV-Vis spectra), fluorescence studies at various temperatures, complemented by XANES synchrotron analyses, have underscored their remarkable thermal and electronic properties. The findings presented here offer a comprehensive framework for the characterization and analysis of TzTz compounds, emphasizing their potential as components in smart electronic and optoelectronic devices.
Materials Science (cond-mat.mtrl-sci), Chemical Physics (physics.chem-ph)
Electrocatalyst discovery through text mining and multi-objective optimization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
The discovery and optimization of high-performance materials is the basis for advancing energy conversion technologies. To understand composition-property relationships, all available data sources should be leveraged: experimental results, predictions from simulations, and latent knowledge from scientific texts. Among these three, text-based data sources are still not used to their full potential. We present an approach combining text mining, Word2Vec representations of materials and properties, and Pareto front analysis for the prediction of high-performance candidate materials for electrocatalysis in regions where other data sources are scarce or non-existent. Candidate compositions are evaluated on the basis of their similarity to the terms conductivity' and dielectric’, which enables reaction-specific candidate composition predictions for oxygen reduction (ORR), hydrogen evolution (HER), and oxygen evolution (OER) reactions. This, combined with Pareto optimization, allows us to significantly reduce the pool of candidate compositions to high-performing compositions. Our predictions, which are purely based on text data, match the measured electrochemical activity very well.
Materials Science (cond-mat.mtrl-sci)
17 pages, 13 figures
Thermoelectric effects in two-dimensional topological insulators
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Z.Z. Alisultanov, E.G. Idrisov, A.V. Kavokin
We explore the nontrivial thermoelectric properties of two-dimensional topological systems. For the Chern insulator, we show that the Seebeck coefficient is fully determined by the Kelvin formula, while the Nernst coefficient vanishes. For a two-dimensional electron gas with Rashba spin-orbit interactions we reveal how the Berry curvature affects the thermoelectric coefficients, and derive the Mott-like equation for thermopower. We predict a strong variation of the thermopower of a two-dimensional topological insulator with time-reversal symmetry in the ballistic and dissipative regimes. The Kelvin formula applies in the ballistic regime, while the Mott formula holds in the dissipative regime. Importantly, in a system with trapezoidal geometry, the combination of ballistic and dissipative regimes leads to the anomalous Nernst effect. Finally, we analyze a two-dimensional Anderson insulator, where edge modes show distinct temperature behavior of the Seebeck coefficient near the weak localization-strong localization transition temperatures. In the trivial phase, the thermopower exhibits a strong power law temperature dependence, while in the topological phase both power law and exponential dependences coexist.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Strongly Correlated Electrons (cond-mat.str-el)
Stabilization of interfaces for double-cation halide perovskites with AVA2FAPb2I7 additives
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Lev O. Luchnikov, Ekaterina A. Ilicheva, Victor A. Voronov, Prokhor A. Alekseev, Mikhail S. Dunaevskiy, Vladislav Kalinichenko, Vladimir Ivanov, Aleksandra Furasova, Daria A. Krupanova, Ekaterina V. Tekshina, Sergey A. Kozyukhin, Dmitry S. Muratov, Maria I. Voronova, Danila S. Saranin, Eugene I. Terukov
The use of mixed cation absorber composition was considered as an efficient strategy to mitigate the degradation effects in halide perovskite solar cells. Despite the reports about partial stabilization at elevated temperatures, unfavorable phase transition after thermocycling and electric field-driven corrosion remains critical bottlenecks of perovskite thin-films semiconductors. In this work, we developed stabilized heterostructures based on CsFAPbI3, modified with mechanically synthesized quasi-2D perovskite incorporating the 5-ammonium valeric acid cation (AVA2FAPb2I7). We found that integration of AVA2FAPb2I7 into grain boundaries boosts phase resilience under harsh thermocycling from -10 up to 100 C and suppresses transitions, as well as decomposition to PbI2. The rapid oxidation of metal contacts in the multi-layer stacks with non-passivated CsFAPbI3 was effectively suppressed in the fabricated heterostructure. A comprehensive interface study of the copper electrode contact revealed that the incorporation of AVA2FAPb2I7 stabilized the lead and iodine states and suppressed contamination of FA cation in ambient conditions. Meanwhile, the metal-perovskite interface remained predominantly in the Cu(0)-Cu(I) state. The observed stabilization in perovskite heterostructure was attributed to an increased activation energy for delta-phase accumulation at the grain boundaries combined with reduced ionic diffusion. The obtained results opened important highlights for the mechanisms of the improved phase stability after thermal cycling and mitigation of the interface corrosion and under an applied electric field.
Materials Science (cond-mat.mtrl-sci)
Superconductivity and pair density waves from nearest-neighbor interactions in frustrated lattice geometries
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Eeli O. Lamponen, Sofia K. Pöntys, Päivi Törmä
We consider superconductivity and pair density waves (PDWs) arising from off-site pairing in frustrated lattice geometries. We express the pair susceptibility in a generic form that highlights the importance of both the density of states, and the quantum geometry of the eigenstates and calculate the superfluid weight (stiffness) as well as the Berezinskii-Kosterlitz-Thouless (BKT) temperature. Paradigmatic bipartite (Lieb) and non-bipartite (kagome) lattices are studied as examples. For bipartite lattices, nearest-neighbor pairing vanishes in a flat band. In the Lieb lattice flat band, we find a PDW at a finite interaction and show that its pair wave vector is determined by the quantum geometry of the band. In the kagome flat band, nearest-neighbor pairing is possible for infinitesimal interactions. At the kagome van Hove singularity, the pair susceptibility predicts a PDW due to sublattice interference, however, we find that its stiffness is zero due to the shape of the Fermi surface. Our results indicate that nearest-neighbor pairing at flat band and van Hove singularities is strongly influenced by the geometric properties of the eigenfunctions, and it is crucial to determine the superfluid weight of the superconducting and PDW orders as it may contradict the predictions by pairing susceptibility.
Superconductivity (cond-mat.supr-con)
Dynamics of transport by helical edge states
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Luis Alberto Razo López, Pierre Wulles, Geoffroy J. Aubry, Sergey E. Skipetrov, Fabrice Mortessagne
Topologically nontrivial band structure of a material may give rise to special states that are confined to the material’s boundary and protected against disorder and scattering. Quantum spin Hall effect (QSHE) is a paradigmatic example of phenomenon in which such states appear in the presence of time-reversal symmetry in two dimensions. Whereas the spatial structure of these helical edge states has been largely studied, their dynamic properties are much less understood. We design a microwave experiment mimicking QSHE and explore the spatiotemporal dynamics of unidirectional transport of optical angular momentum (or pseudospin) by edge states. Pseudospin-polarized signal propagation is shown to be immune to scattering by defects introduced along the edge. Its velocity is two to three orders of magnitude slower than the speed of light in the free space, which may have important consequences for practical applications of topological edge states in modern optical and quantum-information technologies.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
6 Pages, 4 figures, Supplemental Material included at the end
Influence of boundary geometry on active patterns
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
Jigyasa Watwani, Sakshi Pahujani, V Jemseena, Vishal Vasan, K Vijay Kumar
Mechanochemical patterns arising in the actomyosin cortex drive many cellular processes. Here we consider a hydrodynamic model for the actomyosin cortex of cells and study the sensitivity of the emergent patterns to both physical parameters and the geometry of the confining domain. We first establish a general framework for the Galerkin analysis of such patterns far from the linear stability regime on an arbitrary two-dimensional domain. In the case of a circular disk, our analytical results predict transitions from isotropic to anisotropic patterns upon changing the strength of the active stress and the turnover rate. We confirm the existence of these genuine nonlinear bifurcations by an explicit numerical analysis of our model. Extending our numerical analysis to harmonic deformations of the circular disk, we show that the emergent patterns are also sensitive to the curvature of the domain. In particular, the actomyosin patterns resulting from our study closely resemble those seen in cells confined to micropatterned substrates. Our study demonstrates the role of geometry in controlling patterns within the context of a simple model for the actomyosin cortex.
Statistical Mechanics (cond-mat.stat-mech)
Noise-to-current ratio divergence as a fingerprint of dispersing Majorana edge modes
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Leo Katayama, Andreas P. Schnyder, Yasuhiro Asano, Satoshi Ikegaya
The definitive detection of Majorana modes in topological superconductors is a key issue in condensed matter physics. Here we propose a smoking-gun experiment for the detection of one-dimensional dispersing Majorana edge modes, based on theoretical results for multi-terminal transport in a setup consisting of two normal metal leads and a topological superconductor. In the proposed device, the unpaired nature of the Majorana edge modes inherently leads to the absence of the charge current in the linear response regime, while the current fluctuation remains significant. Therefore, the divergence in the noise-to-current ratio serves as unambiguous evidence for the presence of the dispersing Majorana edge modes. We reach this conclusion analytically, without relying on any specific model of topological superconductors. In addition, using tight-binding models of topological-insulator-based topological superconductors, we numerically verify the predicted divergent noise-to-current ratio. We also discuss the application of our proposal to the CoSi$_2$/TiSi$2$ heterostructure and the iron-based superconductor FeTe${1-x}$Se$_x$.
Superconductivity (cond-mat.supr-con), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Large Language Models Are Innate Crystal Structure Generators
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Jingru Gan, Peichen Zhong, Yuanqi Du, Yanqiao Zhu, Chenru Duan, Haorui Wang, Carla P. Gomes, Kristin A. Persson, Daniel Schwalbe-Koda, Wei Wang
Crystal structure generation is fundamental to materials discovery, enabling the prediction of novel materials with desired properties. While existing approaches leverage Large Language Models (LLMs) through extensive fine-tuning on materials databases, we show that pre-trained LLMs can inherently generate stable crystal structures without additional training. Our novel framework MatLLMSearch integrates pre-trained LLMs with evolutionary search algorithms, achieving a 78.38% metastable rate validated by machine learning interatomic potentials and 31.7% DFT-verified stability via quantum mechanical calculations, outperforming specialized models such as CrystalTextLLM. Beyond crystal structure generation, we further demonstrate that our framework can be readily adapted to diverse materials design tasks, including crystal structure prediction and multi-objective optimization of properties such as deformation energy and bulk modulus, all without fine-tuning. These results establish pre-trained LLMs as versatile and effective tools for materials discovery, opening up new venues for crystal structure generation with reduced computational overhead and broader accessibility.
Materials Science (cond-mat.mtrl-sci), Machine Learning (cs.LG)
Preprint, 18 pages
Linear magnetoresistance, anomalous Hall effect and de Haas-van Alphen oscillations in antiferromagnetic SmAg$_2$Ge$_2$ single crystals
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Kanchan Bala, Rahul Verma, Shovan Dan, Suman Nandi, Ruta Kulkarni, Bahadur Singh, A. Thamizhavel
Understanding the interplay among magnetism, electron correlations, and complex electronic structures in rare-earth materials requires both high-quality single crystals and systematic investigation of their electronic properties. In this study, we have successfully grown a single crystal of SmAg$_2$Ge$_2$ and investigated its anisotropic physical properties and de Haas-van Alphen (dHvA) quantum oscillations through experimental and theoretical approaches. SmAg$_2$Ge$_2$ crystallizes in the well known ThCr$_2$Si$2$-type tetragonal structure with lattice parameters, $a=4.226$Å and $c=11.051$~Å. Electrical transport and magnetization measurements indicate that it is metallic and exhibit antiferromagnetic ordering below the Néel temperature, $T{\rm N}$ = 9.2K. SmAg$_2$Ge$_2$ exhibits a linear non-saturating magnetoresistance, reaching $\sim 97$% at $2$K for applied magnetic field $B$$\parallel[001]$ and a significant anomalous Hall effect with an anomalous Hall angle of $0.10-0.14$. Additionally, magnetization measurements reveal dHvA quantum oscillations for magnetic fields greater than $8$~T. Our calculated electronic structure, quantum oscillations, and anomalous Hall effect in the canted antiferromagnetic state closely align with experimental results, underscoring the role of complex electronic structure and spin-canting-driven non-zero Berry curvature in elucidating the physical properties of SmAg$_2$Ge$_2$
Strongly Correlated Electrons (cond-mat.str-el)
Ferroelectricity in the nematic liquid crystal under the direct current electric field
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Mateusz Mrukiewicz, Paweł Perkowski, Jakub Karcz, Przemysław Kula
We investigated the electrical properties of the liquid crystal compound, known as an RM734, exhibiting a ferroelectric nematic phase. The influence of alternating (AC) and direct (DC) current electric fields on the switching process of the polarization vector and dielectric constant of planarly aligned ferronematic and nematic phases were examined. The decrease of the real part of electric permittivity in the ferronematic phase and the creation of ferroelectric order in the nematic phase under the DC field were demonstrated. The analysis of the results reveals the latching of the ferroelectric state. The applied DC field created a ferroelectric mode in the nematic phase. A new model of collective and molecular relaxations considering the domain structure of the ferronematic phase was proposed. The temperature and DC field dependence of dielectric properties were shown. The spontaneous polarization was measured using the field reversal technique. The spontaneous polarization value exhibits a maximum at the fixed temperature.
Soft Condensed Matter (cond-mat.soft)
Phys. Chem. Chem. Phys., 2023,25, 13061-13071
Photon-drag photovoltaic effects and quantum geometric nature
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
The bulk photovoltaic effect (BPVE) generates a direct current photocurrent under uniform irradiation and is a nonlinear optical effect traditionally studied in non-centrosymmetric materials. The two main origins of BPVE are the shift and injection currents, arising from transitions in electron position and electron velocity during optical excitation, respectively. Recently, it was proposed that photon-drag effects could unlock BPVE in centrosymmetric materials. However, experimental progress remains limited. In this work, we provide a comprehensive theoretical analysis of photon-drag effects inducing BPVE (photon-drag BPVE). Notably, we find that photon-drag BPVE can be directly linked to quantum geometric tensors. Additionally, we propose that photon-drag shift currents can be fully isolated from other current contributions in non-magnetic centrosymmetric materials. We apply our theory explicitly to the 2D topological insulator $1T’$-WTe$_2$. Furthermore, we investigate photon-drag BPVE in a centrosymmetric magnetic Weyl semimetal, where we demonstrate that linearly polarized light generates photon-drag shift currents.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), Optics (physics.optics)
7 pages, 3 figures, plus Supplementary Material
PNAS 122, e2424294122 (2025)
Dual tunability of selective reflection by light and electric field for self-organizing materials
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Mateusz Mrukiewicz, Martin Cigl, Paweł Perkowski, Jakub Karcz, Věra Hamplová, Alexej Bubnov
The oblique helicoidal structure is formed in right-angle cholesterics under the applied electric field. The electric field changes the pitch and cone angle but preserves the single-harmonic modulation of the refractive index. As a result, in such a supramolecular system, we can tune the selective reflection of light in a broad range. Here, we report that structural colors can be tuned by simultaneously illuminating the structure with UV light and the action of an electric field. The cholesterics with the oblique helicoidal structure were doped with newly designed rod-like, chiral, and bent-shaped azo-photosensitive materials characterized by a very low rate of thermal back isomerization. The isomerization of the photo-active compounds under UV light causes the red shift of the selective light reflection in the cholesteric mixtures. We found that the molecular structure of the photosensitive materials used affects the reflection coefficient, bandwidth, response time to UV irradiation, and tuning range. The effect was explained by considering the effect of molecular matching, cis-trans isomerization, and electric field action. We investigated the dynamics of molecular changes in the oblique helicoidal structure under the influence of external factors. The designed supramolecular system has the potential application in soft matter UV detectors.
Soft Condensed Matter (cond-mat.soft)
Journal of Molecular Liquids 400, 124540 (2024)
Melting of non reciprocal solids: how dislocations propel and fission in flowing crystals
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Stéphane Guillet, Alexis Poncet, Marine Le Blay, William.T. M Irvine, Vincenzo Vitelli, Denis Bartolo
When soft matter is driven out of equilibrium its constituents interact via effective interactions that escape Newton’s action-reaction principle. Prominent examples include the hydrodynamic interactions between colloidal particles driven in viscous fluids, phoretic interactions between chemically active colloids, and quorum sensing interactions in bacterial colonies. Despite a recent surge of interest in non-reciprocal physics a fundamental question remains : do non-reciprocal interactions alter or strengthen the ordered phases of matter driven out of equilibrium? Here, through a combination of experiments and simulations, we show how nonreciprocal forces propel and fission dislocations formed in hydrodynamically driven Wigner crystals. We explain how dislocation motility results in the continuous reshaping of grain-boundary networks, and how their fission reaction melts driven crystals from their interfaces. Beyond the specifics of hydrodynamics, we argue theoretically that topological defects and nonreciprocal interactions should invariably conspire to deform and ultimately destroy crystals whose the elementary units defy Newton’s third law
Soft Condensed Matter (cond-mat.soft)
11 pages, 5 figures
The $s\pm$ pairing symmetry in the pressured La$_3$Ni$_2$O$_7$ from electron-phonon coupling
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Yucong Yin, Jun Zhan, Boyang Liu, Xinloong Han
The recently discovered bilayer Ruddlesden-Popper nickelate La$3$Ni$2$O$7$ exhibits superconductivity with a remarkable transition temperature $T_c\approx 80 $ K under applied pressures above 14.0 GPa. This discovery of new family of high-temperature superconductors has garnered significant attention in the condensed matter physics community. In this work, we assume the this high-temperature superconductor is mediated by phonons and investigate the pairing symmetry in two distinct models: (i) the full-coupling case, where the Ni-$d{x^2-y^2}$ and Ni-$d{3z^2-r^2}$ orbitals are treated equally in both interlayer and intralayer coupling interactions, and (ii) the half-coupling case, where the intralayer coupling involves only the $d{x^2-y^2}$ orbital, while the interlayer coupling is restricted to the $d_{3z^2-r^2}$ orbital. Our calculations reveal that the interlayer coupling favors an $s\pm$-wave superconducting state, whereas the intralayer coupling promotes an $s++$-wave symmetry. Additionally, we discuss the implications of pair-hopping interactions on the superconducting properties. These findings provide valuable insights into the pairing mechanisms and symmetry of this newly discovered high-temperature superconductor.
Superconductivity (cond-mat.supr-con)
7 pages, 7 figures
Optical response of the supersolid polaron
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-03-03 20:00 EST
Laurent H. A. Simons, Ralf Klemt, Tilman Pfau, Michiel Wouters, Jacques Tempere
The ground-state properties of the supersolid polaron consisting of a neutral impurity immersed in a dipolar supersolid have recently been studied. Here, the optical response of an impurity in a dipolar supersolid is calculated and interpreted in terms of the contributions of the different excitation modes of the supersolid. The optical absorption spectrum reveals the two Van Hove singularities that correspond to the flattening of the two Goldstone modes of the supersolid at the Brillouin zone edge. A single peak is found in the superfluid regime corresponding to the roton minimum which diverges at the transition. We propose the response of an ionic impurity as an experimental probe for the supersolid excitations and show how this technique can be extended to neutral impurities with an electric or magnetic dipole moment.
Quantum Gases (cond-mat.quant-gas)
6 pages, 4 figures
Comparative Analysis of Granular Material Flow: Discrete Element Method and Smoothed Particle Hydrodynamics Approaches
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Jaekwang Kim, Hyo-Jin Kim, Hyung-Jun Park
We compare two widely used Lagrangian approaches for modeling granular materials: the Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPH). DEM models individual particle interactions, while SPH treats granular materials as a continuum using constitutive rheological models. In particular, we employ the Drucker Prager viscoplastic model for SPH. By examining key parameters unique to each method, such as the coefficient of restitution in DEM and the dilatancy angle in SPH, we assess their influence on two dimensional soil collapse predictions against experimental results. While DEM requires computationally expensive parameter calibration, SPH benefits from a continuum scale rheological model, allowing most parameters to be directly determined from laboratory measurements and requiring significantly fewer particles. However, despite its computational efficiency, viscoplastic SPH struggles to capture complex granular flow behaviors observed in DEM, particularly in rotating drum simulations. In contrast, DEM offers greater versatility, accommodating a broader range of flow patterns while maintaining a relatively simple model formulation. These findings provide valuable insights into the strengths and limitations of each method, aiding the selection of appropriate modeling techniques for granular flow simulations.
Soft Condensed Matter (cond-mat.soft), Computational Physics (physics.comp-ph)
Non-Gaussian velocity distributions Maxwell would understand
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
In 1988, Constantino Tsallis proposed an extension of the Boltzmann statistical mechanics by postulating a new entropy formula, $S_q = k_B\ln_q W$, where $W$ is the number of microstates accessible to the system, and $\ln_q$ defines a deformation of the logarithmic function. This top-down" , approach recovers the celebrated Boltzmann entropy in the limit $q \rightarrow 1$ since $S_1 = k_B\ln W$. However, for $q\neq 1$ the entropy is non-additive and has been successfully applied for a variety of phenomena ranging from plasma physics to cosmology. For a system of particles, Tsallis' formula predicts a large class of power-law velocity distributions reducing to the Maxwellian result only for a particular case. Here a more pedagogical bottom-up” path is adopted. We show that a large set of power-law distributions for an ideal gas in equilibrium at temperature T is derived by slightly modifying the seminal Maxwell approach put forward in 1860. The emergence of power-laws velocity distribution is not necessarily related with the presence of long-range interactions. It also shed some light on the long-standing problem concerning the validity of the zeroth law of thermodynamics in this context. Potentially, since the new method highlights the value of hypotheses in the construction of a basic knowledge, it may have an interesting pedagogical and methodological value for undergraduate and graduate students of physics and related areas.
Statistical Mechanics (cond-mat.stat-mech)
14 pages, 3 figures and 2 tables
Enhanced Electromechanical Properties of Solution-Processed K${0.5}$Na${0.5}$NbO$_{3}$ Thin Films
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Nagamalleswara Rao Alluri, Longfei Song, Stephanie Girod, Barnik Mandal, Juliette Cardoletti, Vid Bobnar, Torsten Granzow, Veronika Kovacova, Adrian-Marie Philippe, Emmanuel Defay, Sebastjan Glinsek
K${0.5}$Na${0.5}$NbO${3}$ is among the most promising lead-free piezoelectrics. While its sputtered films match the performance of the champion piezoelectric Pb(Zr,Ti)O${3}$, processing of high-quality, reproducible, and time-stable solution-processed K${0.5}$Na${0.5}$NbO${3}$ films remains challenging. Here, we report 1 $\mu$m-thick Mn-doped K${0.5}$Na${0.5}$NbO${3}$ films prepared through a chemical solution deposition process, which have perfectly dense microstructure and uniform composition across their thickness. The films exhibit a high transverse piezoelectric coefficient (e${31,f}$ = -14.8 C/m$^{2}$), high dielectric permittivity (${\epsilon}{r}$ = 920), low dielectric losses (tan${\delta}$ = 0.05) and can withstand electric fields up to at least 1 MV/cm. The functional properties show excellent stability over time, and the synthesis process is reproducible. The results demonstrate the high potential of Mn-doped K${0.5}$Na${0.5}$NbO${3}$ films to become a replacement for lead-based Pb(Zr,Ti)O${3}$ films in piezoelectric applications.
Materials Science (cond-mat.mtrl-sci)
Critical exponents of the spin glass transition in a field at zero temperature
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-03-03 20:00 EST
Maria Chiara Angelini, Saverio Palazzi, Giorgio Parisi, Tommaso Rizzo
We analyze the spin glass transition in a field in finite dimension $D$ below the upper critical dimension directly at zero temperature using a recently introduced perturbative loop expansion around the Bethe lattice solution. The expansion is generated by the so-called $M$-layer construction, and it has $1/M$ as the associated small parameter. Computing analytically and numerically these non-standard diagrams at first order in the $1/M$ expansion, we construct an $\epsilon$-expansion around the upper critical dimension $D_\text{uc}=8$, with $\epsilon=D_\text{uc}-D$. Following standard field theoretical methods, we can write a $\beta$ function, finding a new zero-temperature fixed-point associated with the spin glass transition in a field in dimensions $D<8$. We are also able to compute, at first order in the $\epsilon$-expansion, the three independent critical exponents characterizing the transition, plus the correction-to-scaling exponent.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
Spontaneous Anomalous Hall Effect in Two-Dimensional Altermagnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
The anomalous Hall effect (AHE) is an efficient tool for detecting the Néel vector in collinear compensated magnets with spin-split bands, known as altermagnets (AMs). Here, we establish design principles for obtaining non-zero anomalous Hall conductivity in the recently proposed two-dimensional (2D) AMs using spin and magnetic group symmetry analysis. We show that only two of the seven nontrivial spin layer groups exhibit an unconventional in-plane AHE in which the Néel vector lies within the plane of the Hall current. Through first-principles simulations on bilayers of MnPSe$_3$ and MnSe, we demonstrate the validity of our group theoretic framework for obtaining AHE with $d$ and $i$-wave altermagnetic orders, depending on the stacking of the bilayers. We find that the spin group symmetry is successful in determining the linear and cubic dependence of anomalous Hall conductivity in Néel vector space, although AHE is a relativistic effect. This work shows that the AHE in 2D AMs can probe the altermagnetic order and Néel vector reversal, thereby facilitating the miniaturization of altermagnetic spintronics.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Single-crystalline CrSb(0001) thin films grown by dc magnetron co-sputtering
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
S. P. Bommanaboyena, C. Müller, M. Jarošová, K. Wolk, S. Telkamp, P. Zeng, F. Křížek, K. Olejník, D. Scheffler, K. Beranová, S. Banerjee, M. Ledinský, H. Reichlová, T. Jungwirth, L. Horák, D. Kriegner
The recent discovery of altermagnetism has sparked renewed interest in the growth of epitaxial films of the NiAs-phase polymorph of CrSb. This paper describes the magnetron sputtering-based fabrication and characterization of high-quality single crystalline CrSb(0001) thin films supported by an isostructural non-magnetic PtSb buffer. X-ray diffraction and scanning transmission electron microscopy show that the films are phase-pure and possess a very high crystalline quality (mosaicity ~0.05 deg), while also being free of extended crystallographic defects. Both scanning electron microscopy and atomic force microscopy confirm their smooth and homogeneous topography. Additionally, the elemental composition of our films was found to be close to stoichiometric via electron probe microanalysis and X-ray fluorescence. Thus, the developed samples represent an ideal platform for further investigation of the material properties of CrSb.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Extremely large magnetoresistance and chiral anomaly in the nodal-line semimetal ZrAs2
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Junjian Mi, Sheng Xu, Shuxiang Li, Chenxi Jiang, Zheng Li, Qian Tao, Zhu-An Xu
We performed the detailed magnetotransport measurements and first principle calculations to study the electronic properties of the transition metal dipnictides ZrAs2, which is a topological nodal-line semimetal. Extremely large unsaturated magnetoresistance (MR) which is up to 1.9 \ast 10^4 % at 2 K and 14 T was observed with magnetic field along the c-axis. The nonlinear magnetic field dependence of Hall resistivity indicates the multi-band features, and the electron and hole are nearly compensated according to the analysis of the two-band model, which may account for the extremely large unsaturated MR at low temperatures. The evident Shubnikov-de Haas (SdH) oscillations at low temperatures are observed and four distinct oscillation frequencies are extracted. The first principle calculations and angle-dependent SdH oscillations reveal that the Fermi surface consists of three pockets with different anisotropy. The observed twofold symmetry MR with electric field along the b-axis direction is consistent with our calculated Fermi surface structures. Furthermore, the negative magnetoresistance (NMR) with magnetic field in parallel with electric field is observed, which is an evident feature of the chiral anomaly.
Materials Science (cond-mat.mtrl-sci)
Front. Phys. in press
Raman Signatures of Single Point Defects in Hexagonal Boron Nitride Quantum Emitters
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Chanaprom Cholsuk, Asli Cakan, Volker Deckert, Sujin Suwanna, Tobias Vogl
Point defects in solid-state quantum systems are vital for enabling single-photon emission at specific wavelengths, making their precise identification essential for advancing applications in quantum technologies. However, pinpointing the microscopic origins of these defects remains a challenge. In this work, we propose Raman spectroscopy as a robust strategy for defect identification. Using density functional theory, we systematically characterize the Raman signatures of 100 defects in hexagonal boron nitride (hBN) spanning periodic groups III to VI, encompassing around 30,000 phonon modes. Our findings reveal that the local atomic environment plays a pivotal role in shaping the Raman lineshape, enabling the narrowing of potential defect candidates. Furthermore, we demonstrate that Raman spectroscopy can differentiate defects based on their spin and charge states as well as strain-induced variations, implying the versatility of this approach. Therefore, this study not only provides a comprehensive theoretical database of Raman spectra for hBN defects but also establishes a novel experiment framework for using tip-enhanced Raman spectroscopy to identify point defects. More broadly, our approach offers a universal method for defect identification in any quantum materials.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Computational Physics (physics.comp-ph), Quantum Physics (quant-ph)
13 pages, 4 figures
Synthesis and characterizations of arsenic doped FeSe bulks
New Submission | Superconductivity (cond-mat.supr-con) | 2025-03-03 20:00 EST
Priya Singh, Manasa Manasa, Mohammad Azam, Tatiana Zajarniuk, Konrad Kwatek, Tomasz Cetner, Andrzej Morawski, Jan Mizeracki, Shiv J. Singh
FeSe(11) family has a simple crystal structure belonging to iron-based superconductors (FBS) and has many stable phases including hexagonal and tetragonal structures, but only the tetragonal phase exhibits the superconductivity. In this study, we have investigated the effects of chemical pressure induced by As-doping at Se-sites in the FeSe system by preparing a series of FeSe1-xAsx (x = 0.005, 0.01, 0.02, 0.05, 0.1, and 0.2) bulks. A broad characterization has been performed on these samples using structural, microstructural, transport, and magnetic measurements. The obtained lattice parameters are increased by As-doping, which suggests the successful insertion of As at Se-sites into the tetragonal lattice for low doping contents up to 5%, whereas the higher As-substitution appears in the form of the FeAs impurity phase. The temperature dependence of the resistivity of all samples has similar behaviour and depicts the highest onset transition temperature of around 11.5 K, but the zero resistivity is not reached until the measured temperature of 7 K, which could be due to the presence of the impurity phases. Our study suggests that a dopant with a large ionic radius, i.e., Arsenic, promotes the formation of the hexagonal phase of the 11 family and is effective for a small amount of doping level for the superconducting properties, whereas higher As-doping levels reduce the superconducting properties.
Superconductivity (cond-mat.supr-con), Materials Science (cond-mat.mtrl-sci)
18 pages, 6 figures
Multiple magnetic states, valley electronics, and topological phase transitions in two-dimensional Janus XYZH (X = Sc, Y, La, Y = Cl, Br, I, and Z = S, Se, Te): From monolayers to bilayers
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Xinyu Tian, Zixuan Zhang, Lixiu Guan, Xiaobiao Liu, Xiaoyu Zhao, Linyang Li
Exploring the coupling between layer, magnetism, valley, and topology in two-dimensional (2D) materials is an important approach to deepen our understanding of materials properties. We propose 27 stable ferromagnetic semiconductor monolayers of Janus XYZH (X = Sc, Y, La, Y = Cl, Br, I, and Z = S, Se, Te). All these monolayers exhibit spontaneous valley polarization, forming ferrovalley (FV) monolayers, showing anomalous valley Hall (AVH) effect. By applying external strain, the topological phase transitions including quantum anomalous Hall (QAH) effect can be introduced. In the ScBrSH bilayer system, AA and AB stacking configurations were constructed through interlayer sliding and rotational operation. The bilayer system exhibits interlayer antiferromagnetic (AFM) ordering with spontaneous valley polarization differing from the FV observed in monolayers. The sliding ferroelectricity observed in the AA stacking indicates that the system exhibits significant multiferroic characteristics. Further analysis shows that interlayer sliding can introduce a layer polarization anomalous valley Hall (LPAVH) effect, which can be precisely controlled by tuning the direction of the ferroelectric polarization. Upon applying external strain, the quantum layer spin Hall (QLSH) effect observed during the topological phase transition in the bilayer can be regarded as the superposition of two QAH monolayers. Furthermore, applying a twisting operation to the bilayer induces unexpected altermagnetism. Our study systematically reveals the rich physical properties of 2D XYZH materials, providing important theoretical foundations and guidance for the design and development of next-generation quantum devices.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Self-Assembly of Delta-Formamidinium Lead Iodide Nanoparticles to Nanorods: Study of Memristor Properties and Resistive Switching Mechanism
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Chinnadurai Muthu, A. N. Resmi, Avija Ajayakumar, N. E. Aswathi Ravindran, G. Dayal, K. B. Jinesh, Konrad Szaciłowski, Chakkooth Vijayakumar
In the quest for advanced memristor technologies, this study introduces the synthesis of delta-formamidinium lead iodide nanoparticles and their self-assembly into nanorods.
Materials Science (cond-mat.mtrl-sci), Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Small, 2024, 20, 2304787 June 26, 2024 2304787
Applications of Enhanced Sampling Methods to Biomolecular Self-Assembly: A Review
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Mason Hooten, Het Patel, Yiwei Shao, Rishabh Kumar Singh, Meenakshi Dutt
This review article discusses some common enhanced sampling methods in relation to the process of self-assembly of biomolecules. An introduction to self-assembly and its challenges is covered followed by a brief overview of the methods and analysis for replica-exchange molecular dynamics, umbrella sampling, metadynamics, and machine learning based techniques. Applications of select methods towards peptides, proteins, polymers, nucleic acids, and supramolecules are discussed. Finally, a short discussion of the future directions of some of these methods is provided.
Soft Condensed Matter (cond-mat.soft)
Hidden States and Dynamics of Fractional Fillings in tMoTe2 Moiré Superlattices
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Yiping Wang, Jeongheon Choe, Eric Anderson, Weijie Li, Julian Ingham, Eric A. Arsenault, Yiliu Li, Xiaodong Hu, Takashi Taniguchi, Kenji Watanabe, Xavier Roy, Dmitri Basov, Di Xiao, Raquel Queiroz, James C. Hone, Xiaodong Xu, X.-Y. Zhu
The fractional quantum anomalous Hall (FQAH) effect was recently discovered in twisted MoTe2 bilayers (tMoTe2). Experiments to date have revealed Chern insulators from hole doping at v = -1, -2/3, -3/5, and -4/7 (per moiré unit cell). In parallel, theories predict that, between v = -1 and -3, there exist exotic quantum phases, such as the coveted fractional topological insulators (FTI), fractional quantum spin Hall (FQSH) states, and non-abelian fractional states. Here we employ transient optical spectroscopy on tMoTe2 to reveal nearly 20 hidden states at fractional fillings that are absent in static optical sensing or transport measurements. A pump pulse selectively excites charge across the correlated or pseudo gaps, leading to the disordering (melting) of correlated states. A probe pulse detects the subsequent melting and recovery dynamics via exciton and trion sensing. Besides the known states, we observe additional fractional fillings between v = 0 and -1 and a large number of states on the electron doping side (v > 0). Most importantly, we observe new states at fractional fillings of the Chern bands at v = -4/3, -3/2, -5/3, -7/3, -5/2, and -8/3. These states are potential candidates for the predicted exotic topological phases. Moreover, we show that melting of correlated states occurs on two distinct time scales, 2-4 ps and 180-270 ps, attributed to electronic and phonon mechanisms, respectively. We discuss the differing dynamics of the electron and hole doped states from the distinct moiré conduction and valence bands.
Strongly Correlated Electrons (cond-mat.str-el)
19 pages, 4 figures, 13 extended figures
Bayesian Selection for Efficient MLIP Dataset Selection
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
The problem of constructing a dataset for MLIP development which gives the maximum quality in the minimum amount of compute time is complex, and can be approached in a number of ways. We introduce a ``Bayesian selection” approach for selecting from a candidate set of structures, and compare the effectiveness of this method against other common approaches in the task of constructing ideal datasets targeting Silicon surface energies. We show that the Bayesian selection method performs much better than Simple Random Sampling at this task (for example, the error on the (100) surface energy is 4.3x lower in the low data regime), and is competitive with a variety of existing selection methods, using ACE and MACE features.
Materials Science (cond-mat.mtrl-sci)
13 pages, 4 figures
Atomically Modulating Competing Exchange Interactions in Centrosymmetric Skyrmion Hosts GdRu2X2 (X = Si, Ge)
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Dasuni N. Rathnaweera, Xudong Huai, K. Ramesh Kumar, Michal J. Winiarski, Tomasz Klimczuk, Thao T. Tran
Magnetic skyrmions are topologically protected spin states enabling high-density, low-power spin electronics. Despite growing efforts to find new skyrmion host systems, the microscopic mechanisms leading to skyrmion phase transitions at specific temperatures and magnetic fields remain elusive. Here, we systematically study the isostructural centrosymmetric magnets- GdRu2X2 (X = Si and Ge), and the role of X-p orbitals in modifying magnetic exchange interactions. GdRu2Ge2 single crystals, synthesized by arc melting, exhibit two high-entropy pockets associated with skyrmion phases at 0.9 T < H < 1.2 T and 1.3 T < H < 1.7 T, 2 K < T < 30 K-more accessible condition at lower fields and higher temperatures than that in the Si counterpart. Entropy estimations from heat capacity measurements align with magnetization data, and transport studies confirm a topological Hall effect, highlighting the system’s nontrivial spin textures and Berry curvature. Compared to GdRu2Si2, electronic structure and exchange interaction evaluations reveal the more extended Ge-4p orbitals enhance competing exchange interactions in GdRu2Ge2, thereby manifesting the rich skyrmion behavior. This work demonstrates how modifying exchange interactions at the atomic level enables the tunability of topologically nontrivial electronic states while advancing our understanding of skyrmion formation mechanisms for future spintronics.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Holes in silicon are heavier than expected: transport properties of extremely high mobility electrons and holes in silicon MOSFETs
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
J. P. Wendoloski, J. Hillier, S. D. Liles, M. Rendell, Y. Ashlea-Alava, B. Raes, R. Li, S. Kubicek, C. Godfrin, J. Jussot, S. Beyne, D. Wan, Md. M. Rahman, S. Yianni, K. W. Chan, F. E. Hudson, W. H. Lim, K. De Greve, A. S. Dzurak, A. R. Hamilton
The quality of the silicon-oxide interface plays a crucial role in fabricating reproducible silicon spin qubits. In this work we characterize interface quality by performing mobility measurements on silicon Hall bars. We find a peak electron mobility of nearly $40,000,\text{cm}^2/\text{Vs}$ in a device with a $21,\text{nm}$ oxide layer, and a peak hole mobility of about $2,000,\text{cm}^2/\text{Vs}$ in a device with $8,\text{nm}$ oxide, the latter being the highest recorded mobility for a p-type silicon MOSFET. Despite the high device quality, we note an order-of-magnitude difference in mobility between electrons and holes. By studying additional n-type and p-type devices with identical oxides, and fitting to transport theory, we show that this mobility discrepancy is due to valence band nonparabolicity. The nonparabolicity endows holes with a density-dependent transverse effective mass ranging from $0.6m_0$ to $0.7m_0$, significantly larger than the usually quoted bend-edge mass of $0.22m_0$. Finally, we perform magnetotransport measurements to extract momentum and quantum scattering lifetimes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Prospection and dispersal in metapopulations: a perspective from opinion dynamics models
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-03-03 20:00 EST
Dispersal is often used by living beings to gather information from conspecifics, integrating it with personal experience to guide decision-making. This mechanism has only recently been studied experimentally, facilitated by advancements in tracking animal groups over extended periods. Such studies enable the analysis of the adaptive dynamics underlying sequential decisions and collective choices. Here, we present a theoretical framework based on the Voter Model to investigate these processes. The model, originally designed to study opinion or behavioral consensus within groups through imitation, is adapted to include the prospection of others’ decisions as a mechanism for updating personal criteria. We demonstrate that several properties of our model (such as average consensus times and polarization dynamic) can be analytically mapped onto those of the classical Voter Model under simplifying assumptions. Finally, we discuss the potential of this framework for studying more complex scenarios.
Statistical Mechanics (cond-mat.stat-mech)
17 pages, 5 figures
$Δ$-model correction of Foundation Model based on the models own understanding
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Mads-Peter Verner Christiansen, Bjørk Hammer
Foundation models of interatomic potentials, so called universal potentials, may require fine-tuning or residual corrections when applied to specific subclasses of materials. In the present work, we demonstrate how such augmentation can be accomplished via $\Delta$-learning based on the representation already embedded in the universal potentials. The $\Delta$-model introduced is a Gaussian Process Regression (GPR) model and various types of aggregation (global, species-separated, and atomic) of the representation vector are discussed. Employing a specific universal potential, CHGNet [Deng et al., Nat. Mach. Intell. 5, 1031 (2023)], in a global structure optimization setting, we find that it correctly describes the energetics of the “8” Cu oxide, which is an ultra-thin oxide film on Cu(111). The universal potential model even predicts a more favorable structure compared to that discussed in recent DFT-based literature. Moving to sulfur adatom overlayers on Cu(111), Ag(111), and Au(111) the CHGNet model, however, requires corrections. We demonstrate that these are efficiently provided via the GPR-based $\Delta$-model formulated on the CHGNet’s own internal atomic embedding representation. The need for corrections is tracked to the scarcity of metal-sulfur atomic environments in the materials project database that CHGNet is trained on leading to an overreliance on sulfur-sulfur atomic environments. Other universal potentials trained on the same data, MACE-MP0, SevenNet-0, and ORB-v2-only-MPtrj show similar behavior, but with varying degrees of error, demonstrating the general need for augmentation schemes for universal potential models.
Materials Science (cond-mat.mtrl-sci)
10 pages, 9 figures
Approximation of anisotropic pair potentials using multivariate interpolation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
Mohammadreza Fakhraei, Chris A. Kieslich, Michael P. Howard
The interaction between two particles with shape or interaction anisotropy can be modeled using a pairwise potential energy function that depends on their relative position and orientation; however, this function is often challenging to mathematically formulate. Data-driven approaches for approximating anisotropic pair potentials have gained significant interest due to their flexibility and generality but often require large sets of training data, potentially limiting their feasibility when training data is computationally demanding to collect. Here, we investigate the use of multivariate polynomial interpolation to approximate anisotropic pair potentials from a limited set of prescribed particle configurations. We consider both standard Chebyshev polynomial interpolation as well as mixed-basis polynomial interpolation that uses trigonometric polynomials for coordinates along which the pair potential is known to be periodic. We exploit mathematical reasoning and physical knowledge to refine the interpolation domain and to design our interpolants. We test our approach on two-dimensional and three-dimensional model anisotropic nanoparticles, finding satisfactory approximations can be constructed in all cases.
Soft Condensed Matter (cond-mat.soft)
14 pages, 10 figures
Self Consistent Field Theory of isotropic-nematic interfaces and disclinations in a semiflexible molecule nematic
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-03-03 20:00 EST
A Self Consistent Field Theory description of equilibrium, but non uniform, configurations adopted by semi flexible liquid crystal molecules is presented. Two cases are considered, isotropic-nematic phase boundaries, and topological defects in the nematic phase (disclinations). Nematogens are modeled by worm-like chains, with microscopic interaction potential of the Maier-Saupe type, with an added isotropic excluded volume contribution. The thermodynamic fields obtained by numerical minimization of the free energy are the molecular density and the nematic tensor order parameter. Interfaces with both homeotropic and planar alignment are studied, as well as biaxiality and anisotropy around $\pm 1/2$ disclinations. The effects induced by fluid compressibility, interaction strength, and elastic anisotropy that follows from chain flexibility on both types of non-uniform configurations are discussed. Defect core sizes decrease as the system becomes less compressible, eventually reaching a constant value in the incompressible limit. The core size is influenced by the nematic interaction strength and chain persistence length, decreasing as the order increases in the nematic region through manipulation of persistence length and nematic interaction. Additionally, when the far field nematic order is fixed, the core size increases with the persistence length.
Soft Condensed Matter (cond-mat.soft)
Large Seebeck coefficient driven by “pudding mold” flat band in hole-doped CuRhO$_2$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Amitayush Jha Thakur, Maximilian Thees, Franck Fortuna, Emmanouil Frantzeskakis, Daisuke Shiga, Hiromichi Kuriyama, Minoru Nohara, Hidenori Takagi, Hiroshi Kumigashira, Andrés F. Santander-Syro
We report the measurement, using angle-resolved photoemission spectroscopy, of the metallic electronic structure of the hole-doped thermoelectric oxide CuRh${0.9}$Mg${0.1}$O$_2$. The material is found to have a ``pudding mold’’ type band structure, with a nearly flat band edge located near the Fermi level, which is thought to be the origin of the thermoelectric behavior of this material. The experimental data match the density functional theory of the undoped parent compound, simply corrected by a rigid shift of the bands. Transport calculations based on the observed band structure yield a Seebeck coefficient of $\sim 200 ,\mu$V/K for the undoped parent material, consistent with experimental measurements. Our results show that CuRhO$_2$ is a textbook example of how pure band-structural effects can result in a large thermoelectric figure of merit, demonstrating that flat band edges in oxides are a realistic route for the efficient conversion of thermal energy.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
Accepted to Physical Review Materials
Bulk-edge correspondence at the spin-to-integer quantum Hall effect crossover in topological superconductors
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-03-03 20:00 EST
Maksim Parfenov, Igor Burmistrov
The spin and integer quantum Hall effects are two cousins of topological phase transitions in two-dimensional electronic systems. Their close relationship makes it possible to transform spin to integer quantum Hall effect in two-dimensional topological superconductors by continuous increase in a symmetry breaking Zeeman magnetic field. We study peculiarities of bulk-edge correspondence and a fate of massless edge and bulk topological (instantons) excitations at such the crossover.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Disordered Systems and Neural Networks (cond-mat.dis-nn), Superconductivity (cond-mat.supr-con)
Flexible Tuning of Asymmetric Near-field Radiative Thermal Transistor by Utilizing Distinct Phase Change Materials
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-03-03 20:00 EST
Hexiang Zhang, Xuguang Zhang, Fangqi Chen, Mauro Antezza, Yi Zheng
Phase change materials (PCMs) play a pivotal role in the development of advanced thermal devices due to their reversible phase transitions, which drastically modify their thermal and optical properties. In this study, we present an effective dynamic thermal transistor with an asymmetric design that employs distinct PCMs, vanadium dioxide (VO2) and germanium antimony telluride (GST), on either side of the gate terminal, which is the center of the control unit of the near-field thermal transistor. This asymmetry introduces unique thermal modulation capabilities, taking control of thermal radiation in the near-field regime. VO2 transitions from an insulating to a metallic state, while GST undergoes a reversible switch between amorphous (aGST) and crystalline (cGST) phases, each inducing substantial changes in thermal transport properties. By strategically combining these materials, the transistor exhibits enhanced functionality, dynamically switching between states of absorbing and releasing heat by tuning the temperature of gate. This gate terminal not only enables active and efficient thermal management but also provides effective opportunities for manipulating heat flow in radiative thermal circuits. Our findings highlight the potential of such asymmetrically structured thermal transistors in advancing applications across microelectronics, high-speed data processing, and sustainable energy systems, where precise and responsive thermal control is critical for performance and efficiency.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
10 pages, 5 figures
Doping dependence of 2-spinon excitations in the doped 1D cuprate Ba$2$CuO${3+δ}$
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-03-03 20:00 EST
Jiarui Li, Daniel Jost, Ta Tang, Ruohan Wang, Yong Zhong, Zhuoyu Chen, Mirian Garcia-Fernandez, Jonathan Pelliciari, Valentina Bisogni, Brian Moritz, Kejin Zhou, Yao Wang, Thomas P. Devereaux, Wei-Sheng Lee, Zhi-Xun Shen
Recent photoemission experiments on the quasi-one-dimensional Ba-based cuprates suggest that doped holes experience an attractive potential not captured using the simple Hubbard model. This observation has garnered significant attention due to its potential relevance to Cooper pair formation in high-$T_c$ cuprate superconductors. To scrutinize this assertion, we examined signatures of such an attractive potential in doped 1D cuprates Ba$2$CuO${3+\delta}$ by measuring the dispersion of the 2-spinon excitations using Cu $L_3$-edge resonant inelastic X-ray scattering (RIXS). Upon doping, the 2-spinon excitations appear to weaken, with a shift of the minimal position corresponding to the nesting vector of the Fermi points, $q_F$. Notably, we find that the energy scale of the 2-spinons near the Brillouin zone boundary is substantially softened compared to that predicted by the Hubbard model in one-dimension. Such a discrepancy implies missing ingredients, which lends support for the presence of an additional attractive potential between holes.
Strongly Correlated Electrons (cond-mat.str-el)
Accepted by PRL. 6 pages, 3 figures