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Physics Condensed Matter

cond-mat Watch Condensed Matter

Friday 11 September

Statistical Mechanics

Thermodynamic Speed Limits in Isolated Quantum Systems

Rikuya Kobashi

We derive thermodynamic speed limits for isolated quantum systems undergoing finite-time unitary driving. The key ingredient is a set of generalized second-law inequalities: for the Gibbs entropy and for several thermodynamically motivated observational entropies, the entropy production is bounded from below by a function of the Vu–Saito quantum Wasserstein distance between the initial and final coarse-grained states. These inequalities yield lower bounds on the operation time in terms of the average entropy-production rate. We apply the framework to system–bath coarse-graining, local-energy coarse-graining, and diagonal entropy, and illustrate the resulting bounds with numerical and analytically solvable examples. Our results provide a thermodynamic characterization of finite-time state transformations in isolated quantum systems and clarify how coarse-grained entropy production constrains macroscopic reachability.
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Superconductivity

Critical current anisotropy of practical superconductors: analysis methods and application cases

V.V. Guryev, I.V. Kulikov and S.V. Shavkin

The analysis of critical current anisotropy is important for improving superconductor-based devices. This article critically evaluates contemporary techniques for analyzing the angular dependence of critical current in practical superconductors, focusing on second-generation high-temperature superconducting tapes (coated conductors). These techniques are based on the scaling model, vortex path model, or anisotropic pinning model. We present empirical findings on critical current angular dependencies in coated conductors of different chemical compositions. Distinctive features are highlighted: the complex effect of rare-earth substitution in the HTS composition on the pinning landscape, peak asymmetry, and the dependence of critical current on Lorentz force direction at fixed magnetic field direction. The described techniques are then applied to the experimental dataset. A refined anisotropic pinning model is introduced to accurately describe certain observed phenomena. Approximation accuracy of the models is assessed using the coefficient of determination adjusted for the number of fitting variables. The fundamental disparity in interpreting angular dependencies with different models is emphasized. No universal methodology yet comprehensively explains all features or links them to the defective structure of the HTS material. This is a critical gap in understanding superconductor behavior under varying conditions and highlights the need for further research.
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Mesoscale and Nanoscale Physics

Spin-polarized Superconductivity and High-Chern Insulators in Twisted Rhombohedral Graphene Family

Zihao Huo, Zexu Li, Wenxuan Wang et al. (+9 more)

Rhombohedral multilayer graphene has emerged as a remarkably versatile platform for exploring strong correlation driven quantum states arising from low-energy topological flat bands. When reconstructed by the moire superlattice, these bands host a wide range of emergent novel states, including integer and fractional Chern insulators and unconventional superconductivity. Here, we firstly report the simultaneous emergence of widespread spin polarized SC and high Chern insulators in twisted bilayer multilayer RMG system 2+n where n=4,5,6. The SC states in 2+n system exhibit different responses to the in plane magnetic field, with SC being suppressed, enhanced and induced by in plane magnetic field . The latter two are consistent with spin-triplet pairing. Along with SC, angle and layer dependent HCIs with tunable Chern numbers emerge. Moreover, the fractional high Chern insulator in the system survives under high in plane magnetic field which can induce SC in the same device. Our work not only establishs twisted bilayer multilayer rhombohedral graphene as a unified platform for studying SC and high Chern insulators, but also opens a pathway towards multiple copropagating chiral Majorana channels by coupling spin-polarized SC to high Chern insulators.
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All authors Zihao Huo, Zexu Li, Wenxuan Wang, Gengdong Zhou, Qiu Yang, Xin Sui, Zaizhe Zhang, Kenji Watanabe, Takashi Taniguchi, Zhida Song, Kaihui Liu, Xiaobo Lu

Statistical Mechanics

Tensor-network Monte Carlo approach based on time-evolving block decimation

Shimpei Goto, Hidemaro Suwa and Synge Todo

We propose a tensor-network Monte Carlo (TNMC) approach for unitary evolution following the compression sequence of the time-evolving block decimation (TEBD) algorithm. In the TNMC approach, the obtained results contain evaluable statistical errors rather than truncation errors, unlike ordinary singular-value-decomposition-based methods such as the TEBD algorithm. Consequently, one can estimate unbiased expectation values within statistical errors even with a finite bond dimension. Since the sampling scheme is introduced in the simulations of unitary evolution, the proposed Monte Carlo scheme may suffer from a sign problem. We observe that the sign problem can be mitigated by increasing the bond dimension. We apply the proposed TNMC approach to the Hamiltonian and the Floquet dynamics. Numerical experiments show that the TNMC approach can estimate accurate expectation values of observables even when the TEBD method with the same bond dimension cannot. The proposed approach can be a new direction for improving the classical simulatability of unitary evolution.
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Materials Science

Enhancing Conformality in Atomic Layer Deposition through Low Growth Per Cycle

Christine Gonsalves, Jorge A. Velasco, Ahmed Othman et al. (+2 more)

Atomic layer deposition (ALD) is a key enabling technology for advanced microelectronics as it enables the growth of functional thin films on complex three-dimensional substrates with unmatched atomic-scale precision. Conformal film growth in high-aspect-ratio (HAR) structures is limited by slow diffusion of reactant molecules into deep, narrow features. This work elucidates an approach to grow conformal films faster by investigating the relationship between the ALD growth per cycle (GPC) and the film penetration depth in HAR structures through modeling and experiments. Diffusion-reaction simulations reveal, under Knudsen diffusion conditions, an inverse square root relationship between the film penetration depth and GPC. The prediction is validated experimentally with a model zinc oxide ALD process on rectangular lateral HAR structures, using an inhibitor molecule to decrease the GPC. While ALD is traditionally optimized for "high GPC," this work shows that "low GPC" may increase efficiency when conformality is key.
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All authors Christine Gonsalves, Jorge A. Velasco, Ahmed Othman, Ville Miikkulainen, Riikka L. Puurunen

Materials Science

Enhanced anomalous Nernst effect in Pr-doped kagome and honeycomb magnet LaCo$_5$

Zheng Li, Yueyang Wu, Tianhao Li et al. (+7 more)

In this work, we report the successful synthesis of La$_{1-x}$Pr$_x$Co$_5$ ($x = 0.09, 0.21, 0.45$) single crystals. Magnetic field-dependent magnetization measurements reveal that Pr substitution induces negligible changes in the magnetic properties of LaCo$_5$, with the ferromagnetic ordering predominantly governed by the Co sublattices. Remarkably, the doped systems exhibit significant enhancements in the anomalous Nernst effect. At 300~K, the anomalous Nernst thermopower $S^A_{yx}$ reaches 6.5~$\mathrm{\mu V/K}$ in La$_{0.55}$Pr$_{0.45}$Co$_5$, corresponding to a $\sim$ 40 % enhancement compared to the parent compound. This significant improvement can be predominantly attributed to Pr-doping-induced Fermi level modification, which directly leads to a redistribution of Berry curvature across the Fermi surface. This work highlights the effectiveness of Pr doping in boosting the anomalous Nernst effect of La$_{1-x}$Pr$_x$Co$_5$, offering a practical strategy to design advanced materials for room-temperature energy-harvesting technologies and high-efficiency thermal sensing devices.
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All authors Zheng Li, Yueyang Wu, Tianhao Li, Jun-jian Mi, Shu-Xiang Li, Jiang Ma, Qian Tao, Xiaofeng Xu, Sheng Xu, Zhu-An Xu

Mesoscale and Nanoscale Physics

Chirality in Condensed Matter: Symmetry, Waves, and Quasiparticles

Jorge Puebla, Jun-ichiro Kishine, Masashi Shiraishi et al. (+1 more)

Chirality has become a recurring concept throughout condensed-matter physics, appearing in contexts ranging from optical activity and chiral phonons to magnetic excitations and hybrid quasiparticles. As its use has expanded, however, the concept has often become intertwined with related notions such as angular momentum, polarization, helicity, and nonreciprocity, obscuring its precise symmetry-based meaning. Although chirality is universally associated with broken spatial-inversion ($\mathcal{P}$) symmetry and preserved time-reversal ($\mathcal{T}$) symmetry, its physical manifestation and quantitative characterization strongly depend on the system and phenomenon under consideration. In this review, we examine chirality across photons, phonons, magnons, and hybrid excitations. We show that, while no universal measure of chirality exists, different physical systems admit different $\mathcal{P}$-odd and $\mathcal{T}$-even quantities that characterize specific chiral phenomena. We further argue that chirality is often best understood through chirality-selective interactions between waves, matter, and quasiparticles rather than as an intrinsic property of isolated excitations. From this perspective, hybridization provides a particularly promising setting for the emergence, transfer, and control of chirality in condensed-matter systems.
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All authors Jorge Puebla, Jun-ichiro Kishine, Masashi Shiraishi, Konstantin Y. Bliokh

Materials Science

Mechanical control of competing magnetic order in crystalline MnPtGa membranes

R Rawat, F Fei, T Samanta et al. (+5 more)

MnPtGa hosts competing magnetic states, including ferromagnetic, canted antiferromagnetic, and spin density wave (SDW) order in the centrosymmetric $P6_3/mmc$ structure, while a related inversion-broken structure supports chiral skyrmions. Controlling this competition motivates materials platforms that enable tunable strain and symmetry breaking, together with probes of SDW order compatible with ultrathin samples. Here, we demonstrate single crystalline MnPtGa membranes grown by molecular beam epitaxy on graphene/Ge(111) and released by mechanical exfoliation. X-ray and electron diffraction confirm high crystalline quality. SQUID magnetometry reveals a 140 K anomaly in the zero-field-cooled $dM/dT$ that persists after exfoliation, while time-resolved reflectivity shows a coincident peak in the electronic relaxation time consistent with a quasiparticle phonon bottleneck associated with a putative SDW gap. Intentional rippling suppresses the $\sim 140$ K magnetic anomaly, demonstrating mechanical control of the low-temperature state. These results establish MnPtGa membranes as a platform for detecting and strain-tuning competing magnetic orders.
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All authors R Rawat, F Fei, T Samanta, Z LaDuca, K Su, M Arnold, J Xiao, J K Kawasaki

Materials Science

Observation of topological surface phonons in diamond with nonlinear optics

Qi Wang, Xinyi Liu, Xinyue Sheng et al. (+8 more)

Topological quantum states in electronic systems have profoundly transformed the understanding of phases of matter. Recent theories predict novel vibrational topological quantum states, i.e., topological phonons in various solids. However, this paradigm is yet to be established due to the lack of convincing experimental verification of topological surface phonons—a hallmark signature of topological phonon states. Here, we report the discovery of topological surface phonons in diamond using sum-frequency spectroscopy—a nonlinear optical spectroscopy capable of probing surface phonons with high sensitivity. Diamond, known for exceptional hardness and thermal transport, is unveiled as a phonon topological semimetal hosting topological nodal-lines and nexus triple points in the bulk. With consistent theory and experiments, we uncover the resultant topological surface phonons on diamond (111) and (100) surfaces. Moreover, by chemically modifying these surfaces, we reveal the disorder effect on topological surface phonons. These findings pave the way for bridging two fundamental domains: quantum topology and lattice dynamics, besides having important implications on diamond-based devices and functional interfaces.
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All authors Qi Wang, Xinyi Liu, Xinyue Sheng, Zhi-Kang Lin, Xiaowei Lu, Xiaosheng Yang, Peining Li, Yizhou Liu, Chang-Hui Li, Wei-Tao Liu, Jian-Hua Jiang

Materials Science

Revealing Hidden Inversion Symmetry Breaking in ZrTe$_5$ via Phonon-Assisted Heterodyne Amplification

S. J. Li, J. H. Huang, H. Y. Wu et al. (+13 more)

ZrTe$_5$ is a sensitive topological material where small perturbations can alter its electronic structure. Its equilibrium crystal structure has been widely regarded as centrosymmetric, while recent experiments have raised the possibility of inversion-symmetry breaking. Here we probe this hidden symmetry lowering using nonlinear optical spectroscopy. Although conventional second-harmonic generation does not resolve an equilibrium symmetry-breaking signal, terahertz-field-induced second-harmonic generation (TFISH) reveals it through phonon-assisted heterodyne amplification. A coherently driven infrared-active phonon acts as a local oscillator for the vanishingly weak second-order susceptibility $\chi^{(2)}$, converting an otherwise undetectable symmetry-breaking response into a phonon-frequency modulation of the TFISH signal. The field-linear scaling of this modulation demonstrates $\chi^{(2)}$ is an equilibrium susceptibility rather than a response induced by the THz field. Polarization- and temperature-dependent measurements identify a bulk polar distortion along the crystallographic $a$ axis that persists to room temperature, while the $c$ axis remains nonpolar. These results provide direct optical evidence for equilibrium inversion-symmetry breaking in bulk ZrTe$_5$ and establish a structural constraint for understanding its electronic and topological properties.
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All authors S. J. Li, J. H. Huang, H. Y. Wu, S. P. Zheng, C. J. Kong, B. Xu, H. Wang, T. Dong, L. Yue, D. Wu, Y. Wan, Z. L. Li, X. B. Wang, S. J. Zhang, N. L. Wang, Y. T. Li

Superconductivity

Emergent magnetism, heavy electrons and pressure-induced reentrant superconductivity in the iron substituted 4d transition-metal sulfides

Yalei Huang, Lu Xin, Na Zuo et al. (+16 more)

Superconductivity emerging from or in the vicinity of magnetic states is generally considered to be mediated by spin fluctuations and thus lies beyond the scope of conventional electron-phonon coupled BCS framework. Here we report the emergence of novel ferromagnetism in the d-electron rhodium sulfide Rh17S15 superconductor, characterized by an enhanced Sommerfeld coefficient {\gamma} arising from the flat topological band and many-body correlations. We further demonstrate that the ferromagnetism can be tuned via Fe substitution at the Rh sites, leading to a spin glass ground state induced by the competing ferromagnetic and antiferromagnetic exchange interactions. Fe doping results in a further enhancement of both the {\gamma} and electron effective masses. At a doping level of x = 0.67 in Rh17-xFexS15, {\gamma} reaches 312 mJ mol-1K-2, second only to the well-documented d-electron heavy-fermion material LiV2O4. Furthermore, upon applying pressure, superconductivity is first suppressed; under high pressures, however, we observe the reentrant superconductivity in both pristine and Fe-doped samples. Our results not only demonstrate the unusual magnetic states and possible heavy-fermion features in these frustration-free, d-based superconductors, but also suggest that the superconductivity in this system is likely mediated by the intrinsic spin fluctuations and may thus be unconventional.
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All authors Yalei Huang, Lu Xin, Na Zuo, Bin Li, Wei Zhou, Dhanarajagopal Alltrin, Boning Yu, Haiyang Yang, Bin Qian, Wen-Chin Lin, Raman Sankar, Michael Smidman, Xiangzhuo Xing, Chunqiang Xu, Xiaobing Liu, Jianhui Dai, Dong Qian, Shiyan Li, Xiaofeng Xu

Materials Science

Irreducible sub-nm$^2$ ferroelectric domains by 2D-flat polar band in perovskite superlattices

Pawan Kumar and Jun Hee Lee

Flat polar phonon bands in ferroelectrics have been envisioned to realize irreducibly small domains for achieving the highest memory density. However, such bands are extremely rare, with only a one-dimensional flat polar band discovered in ferroelectric hafnia, which gives rise to irreducibly narrow, line-type domains with a half-unit-cell width of 2.7 Angstrom. Here, we report the discovery of a two-dimensional flat polar band in the ferroelectric (BaTiO$_3$)$_1$/(BaXO$_3$)$_1$ superlattice (X = Zr, Sn), which generates extremely localized, noninteracting dipoles within its quarter-unit-cell area that form quasi-degenerate states of irreducible sub-nm$^2$ ferroelectric domains. The estimated ferroelectric domain density, exceeding 300 Tbit/cm$^2$ (assuming one bit per domain) represents a record high among the known ferroelectrics, with independently switchable dipoles at low voltages. The ferroelectric phase hosting two-dimensional flat bands constitutes a competing ground state across superlattice stacking directions and thus can be experimentally realized in both freestanding structures and epitaxial growth on MgO substrates. This discovery opens unprecedented opportunities to explore multidimensional flat polar bands in ferroelectrics and to engineer ultra-dense and low-power memory devices.
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Materials Science

Deterministic patterning and alignment of tellurium quantum wires using nanoscale templates

I K M Reaz Rahman, Scott Dhuey, Moniruzzaman Jamal et al. (+14 more)

Tellurium (Te) is an intriguing one-dimensional (1D) semiconductor that has recently attracted considerable interest as a p-type channel material. However, scalable synthesis methods have lacked control over the orientation and patterning of the Te atomic chains, thus limiting its practical use. Guided by theory, we overcome this challenge using nanowire-shaped templates to achieve oriented, single-crystal growth of Te on amorphous substrates. Strong alignment of Te atomic chains is achieved as template widths are reduced to sub-20 nm. This high structural order, confirmed by 4D scanning transmission electron microscopy, enables the observation of pristine quantum transport phenomena for deterministically patterned Te. Field-effect transistors exhibit well-defined conductance plateaus at 77 K due to population of individual 1D subbands. Furthermore, Coulomb blockade emerges at 1.7 K, with the Te channel acting as a gate-tunable quantum dot. This synthesis approach provides a scalable pathway for integration of Te-based quantum materials for future electronic and quantum technologies.
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All authors I K M Reaz Rahman, Scott Dhuey, Moniruzzaman Jamal, Taehoon Kim, Naoki Higashitarumizu, Selven Virasawmy, Aidar Kemelbay, Genki Ohkatsu, Aditya Nirmale, Inha Kim, Hyong Min Kim, Karen C. Bustillo, Joel W. Ager III, Daryl C. Chrzan, Mary Scott, Yutaka Majima, Ali Javey

Materials Science

$Ab$ $initio$ Study of Substitutional Defects in Li$_{3}$OCl Solid Electrolyte for Li-ion Batteries

Carson D. Ziemke, Naveed Naemi, Ha M. Nguyen et al. (+7 more)

Improving ion transport in solid electrolytes and cathode coatings remains a key challenge for all-solid-state Li-ion batteries because their room-temperature ionic conductivity is still substantially lower than that of liquid electrolytes. In our previous combined experimental and theoretical study, we showed that thermal neutron irradiation enables defect engineering in LiBO$_2$ through the transmutation of $^6$Li and $^{10}$B, generating lattice vacancies that enhance ionic conductivity. Here, we examine whether this approach can be extended to Li$_3$OCl, a representative antiperovskite solid electrolyte. Using density functional theory, we investigate substitutional defects at Li sites involving B, He, and H, associated with B doping and the neutron-capture reactions $^{6}\mathrm{Li}+n\rightarrow\,^{3}\mathrm{H}+\alpha$ and $^{10}\mathrm{B}+n\rightarrow\,^{7}\mathrm{Li}+\alpha+\gamma$. We evaluate defect formation energetics, the resulting structural distortions, and compare these substitutional defects with other mono-, di-, and trication substitutions at Li sites. Our results show that substitutional defects associated with neutron irradiation provide a feasible route to tune the defect chemistry of antiperovskite solid electrolytes and support neutron-driven defect engineering as a strategy for developing advanced materials for high-performance all-solid-state Li-ion batteries.
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All authors Carson D. Ziemke, Naveed Naemi, Ha M. Nguyen, Anthony Dorhauer, Carlos Garcia, Narendirakumar Narayanan, Yangchuan Xin, John Gahl, Thomas W. Heitmann, Carlos Wexler

Thursday 10 September

Other Condensed Matter

Quasi-static loading of granular media as a linear complementarity problem

Matthew R. Kuhn

The discrete quasi-static response of rate-independent dissipative granular media is addressed. Granular systems are conventionally simulated with methods that are intrinsically dynamic, such as the discrete element (DEM) and discontinuous deformation (DDA) methods, with the particles' accelerations and damping being essential aspects. In contrast, quasi-static methods derive from the static stiffness relationships among the particles. With frictional contacts, an assembly's stiffness is incrementally non-linear and dependent on the direction of loading. The paper resolves this difficulty by casting the response as a linear complementarity problem (LCP). The approach benefits from a foundation of past research on existence, uniqueness, and stability of LCP solutions, which are expounded in a concise set of rules. The LCP of a granular system is derived, accounting for geometric effects that arise from curvatures of particles at their contacts, frictional contact stiffnesses, and displacement constraints on the particles. The paper describes eight aberrant conditions (pathologies) of granular systems, in the forms of various bifurcations and instabilities. When placed in the context of an LCP, the eight conditions are unambiguously defined. These pathologies include three types of bifurcation: discrete, continuous-bounded (not yet reported in the literature), and continuous-unbounded. Not yet reported in the literature is an abrupt discontinuous change in movements upon a continuous change of the data. Methods and results are illustrated with examples of granular systems. Results show that instability and bifurcation are pervasive conditions near failure; that failure and softening are sensitive to the geometric contours of the particles at contacts; and that quasi-static systems can encounter states that require a dynamic transition to resolve a lack of paths consistent with loading.
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Materials Science · Cross-listed from physics.chem-ph

Molecular representation shapes the balance between target fidelity and exploration in flow based polymer generation

Tianren Zhang

Designing polymers with targeted properties requires navigating vast chemical spaces from limited labeled data. Here we introduce PolyLatentFlow, a framework based on continuous-time flow matching in latent space for unconditional and conditional polymer generation, together with LlamaUni, a multimodal representation combining polymer sequence and 3D structural information. In unconditional generation, PolyLatentFlow with LlamaUni produced the largest yield of valid candidates novel relative to PolyInfo among the evaluated unconditional generators while maintaining high diversity. For $T_g$ conditioning, generated property distributions shifted systematically across a 200 {\deg}C target range. In multi-property tasks, molecular representations showed similar surrogate target fidelity but differed markedly in validity, training-set replay, and structural proximity to labeled polymers. PolyLatentFlow with LlamaUni consistently combined high validity with low replay and achieved the largest per-attempt yield of nonreplayed target hits for CO$_2$/N$_2$ conditioning. These results demonstrate latent space flow matching for polymer inverse design and identify molecular representation as a key determinant of target control and exploration beyond labeled chemistry.
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Soft Condensed Matter

Self-organisation in hard-soft granular mixtures

Haoran Jiang, Dominik Krengel, Takashi Matsushima et al. (+1 more)

Self-organisation of granular systems is a key determinant of their macroscopic behaviour and has been studied extensively in assemblies of hard particles. We use numerical simulations to test this understanding in mixtures of hard and soft particles, focusing on cells, the smallest irreducible loops of the contact network, as structural descriptors. We show that, while the cell statistics display robust qualitative features under isotropic compaction, they depend on inter-particle friction, $\mu$, and soft-particle fraction, $\kappa$. Specifically, (i) the quadron area distributions retain a $\Gamma$ form, albeit with parameters that vary systematically with $\mu$ and $\kappa$. (ii) Predictions of the cell order distribution (COD) by maximising the entropy, without taking mechanical stability into consideration, become increasingly inaccurate at large cell orders. (iii) Irrespective of $\mu$, the normalised cell stress distributions collapse onto one master Weibull form, whose only shape parameter depends weakly on $\kappa$. This suggests a quasi-universal form that may deteriorate slightly at very high fractions of soft particles. (iv) Cells align preferentially along the local major principal stress direction, showing the same coordinated stress–structure self-organisation as in hard particles. The relative robustness of cell statistics to the addition of soft particles suggests that hard and hard–soft granular mixtures can be described by one model.
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All authors Haoran Jiang, Dominik Krengel, Takashi Matsushima, Raphael Blumenfeld

Strongly Correlated Electrons

Geometric Approach to the High-Throughput Identification of Honeycomb Materials

Lex M. Rouquette and Alannah M. Hallas

The honeycomb lattice is an iconic structural motif in condensed matter physics. However, emerging theoretical models require the identification of new honeycomb lattice materials with strict specification on their structural, magnetic, and electronic characteristics. In this work, we introduce a filtering algorithm using simple geometric arguments to detect materials with honeycomb structural motifs. We classify four unique categories of lattices: conventional honeycombs, hyperhoneycombs, staircase or zigzag honeycombs, and fully 3D honeycombs. We also identify several distortion motifs in the conventional honeycomb set: elongated, sheared, and buckled honeycombs. We describe several screening criteria for further analysis of honeycomb systems, specifically the quantification of exfoliability in 2D materials, the identification of magnetic honeycombs, and a density-of-states peak quality metric for identification of electronic instabilities. The database containing the results of the filters and subsequent analysis is a useful tool for identifying novel materials for targeted physical phenomena for experimental characterization.
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Statistical Mechanics · Cross-listed from gr-qc

Classical and quantum perspectives on temperature in accelerated frames

Babak Vakili

We study the notion of temperature in uniformly accelerated frames within a relativistic thermodynamic framework. Considering a perfect fluid at rest in a non-inertial (Rindler) frame, we derive the condition for thermal equilibrium from energy–momentum conservation. This leads to a position-dependent temperature profile consistent with the Tolman–Ehrenfest relation. We emphasize that this temperature characterizes the local thermodynamic equilibrium of the fluid in the accelerated frame and does not arise from a transformation law between different observers. The physical interpretation of the result and its relation to acceleration-induced effects are briefly discussed.
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Strongly Correlated Electrons

Selective coupling of coherent phonons to intertwined charge-orbital and magnetic orders in doped manganites

X. Liu, M. Sander, S.-W. Huang et al. (+15 more)

Strongly correlated materials feature technologically relevant functionalities such as high-temperature superconductivity and colossal magnetoresistance, which emerges from the competition and coexistence of electronic and magnetic phases. Uncovering the microscopic interactions underlying these phenomena remains challenging because spin, orbital, charge, and lattice degrees of freedom are inherently intertwined. Here, by combining time-resolved X-ray diffraction and polarization-resolved ultrafast optical reflectivity in La1/4Pr3/8Ca3/8MnO3, we reveal that coherent phonon modes can selectively track different ordered phases: the in-plane phonon response is predominantly sensitive to charge/orbital order, and the c-axis phonon response is sensitive to magnetic order. Moreover, a ferromagnetic-related hysteresis emerges even when solely probing the charge/orbital-ordered phase, indicating a strong microscopic coupling between the spatially separated charge/orbital-ordered and ferromagnetic-ordered phases. These results demonstrate that coherent phonons provide a direct time-domain route to disentangle intertwined electronic and magnetic dynamics in coupled phases.
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All authors X. Liu, M. Sander, S.-W. Huang, S. Zerdane, A. Caviezel, M. Rössle, J. Lu, D. Babich, S. Shin, E. Pomjakushina, P. Marsik, L. Wang, S. W. Cheong, C. Jia, P. Beaud, H.T. Lemke, U. Staub, R. Mankowsky

Materials Science

Pseudo-hybrid density functional ACBN0 for Hubbard $U$ correction in a numeric atom-centered orbital basis

Svetlana A. Artiukova, Ilia M. Odud and Sergey V. Levchenko

We present a formulation and implementation of the Agapito-Curtarolo-Buongiorno Nardelli (ACBN0) pseudo-hybrid density functional in a numeric atom-centered orbital basis. The method is realized in the all-electron, full-potential electronic-structure package FHI-aims. The implementation uses a Löwdin-orthogonalized projector, which improved the stability of the self-consistent ACBN0 iterations for the tested systems. For a benchmark set of materials including metal oxides and nitrides, ACBN0 with the fully localized limit (FLL) as the double-counting treatment reduces the aggregate band gap errors relative to the Perdew-Burke-Ernzerhof (PBE) and strongly constrained and appropriately normed (SCAN) functionals, reaching an accuracy comparable to the Heyd-Scuseria-Ernzerhof functional (HSE06). For six bulk transition metal oxides calculated with the same numerical settings, an HSE06 iteration is approximately 13-33 times as expensive as the corresponding ACBN0@PBE iteration with Petukhov mixing. The applicability of the localized-basis implementation to low-dimensional systems is demonstrated by calculations of adsorption and the oxygen evolution reaction (OER) overpotential on a $\beta$-NiOOH(001) surface. On regularized SCAN (rSCAN) relaxed structures, single point ACBN0 based on rSCAN (ACBN0@rSCAN) with the “tight” numerical settings reduces the mean absolute deviation of the reaction-step energies from HSE06 and shifts the estimated overpotential toward the HSE06 and Perdew-Burke-Ernzerhof hybrid (PBE0) reference results.
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Materials Science

Different critical exponents on two sides of the magnetic transition in two dimensions

P. Biswal, Ruma Khatun, G. Tripathy et al. (+2 more)

The possibility of different critical exponents on two sides of a magnetic transition has been theoretically predicted [PRB 13, 2222 (1976), PRL 115, 200601 (2015)] and experimentally realized [PRL 128, 015703 (2022)] in three-dimensional systems. However, the emergence of such a scenario in two dimensions is not yet established. Here, we report distinct two-dimensional (2D) critical exponents below and above the magnetic transition temperature (TC) through critical scaling analysis in a quasi-2D non-centrosymmetric, Dzyaloshinskii-Moriya interaction (DMI) active hybrid perovskite (C7H9NBr)2CuBr4. The system exhibits critical exponents of 2D Ising-type below TC and 2D XY-type above TC . In contrast, isostructural Cl and centrosymmetric Br analogs, in which the DMI effect is expected to be weaker, exhibit symmetric 2D critical behavior. These results highlight the crucial role of DMI in (C7H9NBr)2CuBr4 as a symmetry-breaking perturbation that alters the magnetic critical behavior differently above and below TC . Our study is the experimental realization of hitherto unreported asymmetric 2D critical behavior in structurally flexible and dimensionally tunable hybrid perovskites.
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All authors P. Biswal, Ruma Khatun, G. Tripathy, Diptikanta Swain, D. Samal

Materials Science · Cross-listed from cs.CV

Physics as the label for measuring and correcting materials reasoning in multimodal models

Hasan Kurban, Rasul Khanbayov and Mustafa Kurban

Vision-language and language models increasingly interpret materials data, yet benchmarks report that they hallucinate invalid properties and violate physical law. Evaluation matches final answers to scarce human labels, while discovery agents verify final proposals or density functional theory (DFT) execution. Neither measures the physical consistency of a model's reasoning chain. Materials data carries its own physics, making a large class of materials reasoning verifiable without annotation. We introduce MatPCR, a label-free benchmark whose programmatic oracles check diffraction geometry through Bragg's law, scale bars, spectral peaks, and Materials Project-grounded checks of near-hull stability, computed band-gap class, and net magnetization. We define the Physical-Consistency Rate over image and structure inputs; introduce Constraint-Grounded Self-Verification, an agentic loop whose gain survives self-refinement and equal-compute re-prompting controls; release an open verifier useful in distribution but near chance on all six held-out constraint types; and derive an exact identity for how oracle error displaces the reported rate.
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Materials Science

Functionalization-Driven Charge Redistribution Enabling Ultra-High-Capacity V2B MBene Anode for Li/Na ion batteries: A First-Principles study

Shaiokh Bin Abi and Ahmed Zubair

Amid increasing global demand for clean, sustainable energy, the search for novel electrode materials has emerged as a crucial link to advancing future energy storage technologies. Here, we explored the potential of N-functionalized 2D MBene V2BN2 as anode materials for Li- and Na-ion batteries using first-principles calculations. Phonon dispersion and ab initio molecular dynamics calculations were employed to assess the dynamic and thermal stability of the material. The intrinsic metallic properties of V2BN2 were revealed through electronic band structures and density of states analyses. Importantly, Bader charge analysis demonstrates substantial charge redistribution upon Li/Na adsorption, leading to stronger ion-substrate interactions compared to the pristine counterpart. This redistribution plays a decisive role in enhancing Li/Na ion adsorption and stabilizing ion accommodation. Furthermore, owing to favorable multilayer adsorption of Li and Na ions, V2BN2 exhibited high theoretical specific capacities of 1524 and 762 mAh/g, as well as low open circuit voltages of 0.73 and 0.23 V for Li and Na, respectively. In addition, the energy barriers were calculated to be 0.49 and 0.29 eV for Li- and Na-ion transport, respectively, indicating rapid ion transport and excellent rate capability. These results indicate that V2BN2 holds significant potential as an anode material for next-generation rechargeable ion batteries.
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Soft Condensed Matter

Collective Behavior of Intelligent Active Brownian Particles in the Presence of a Static Obstacle

Surya Narayan Sahoo, Arabinda Bera and Jiarul Midya

Using computer simulations, we investigate the collective behavior of two-dimensional active Brownian particles (ABPs) with excluded-volume interactions in the bulk and in the presence of a single static circular obstacle. Perception-mediated interactions are introduced through a vision-based steering mechanism that enables each particle to reorient its propulsion direction according to the instantaneous positions of neighboring particles within a prescribed vision cone. In the bulk, these intelligent active Brownian particles (iABPs) exhibit distinct collective states, including aggregated clusters, worm-like chains, worm-aggregate coexistence, and dilute gas phases. We characterize these states using a shape anisotropy parameter and construct the corresponding phase diagrams. The presence of a static obstacle, which interacts with the particles through purely repulsive forces, qualitatively alters their collective behavior. In contrast to conventional ABPs, whose isotropic accumulation around the obstacle increases with activity, iABPs exhibit the opposite trend, with boundary accumulation decreasing as the activity increases. We further identify empirical scaling relations that describe particle accumulation and cluster formation at the obstacle boundary. Consequently, the relative effective diffusion coefficient of iABPs displays a nonmonotonic dependence on self-propulsion speed, whereas that of conventional ABPs decreases monotonically with increasing activity. In addition, we show that the residence times of iABPs are orders of magnitude shorter than those of conventional ABPs, indicating that perception-mediated interactions can be useful for controlling the organization and transport of active particles in complex environments.
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Materials Science · Cross-listed from cs.AI

Mined from Scientific Literature: Process Schemas for Atomic Layer Deposition and Etching in Materials Science

Sameer Sadruddin, Eleni Poupaki, Alex Watkins et al. (+5 more)

Atomic layer deposition (ALD) and atomic layer etching (ALE) are reported heterogeneously across experimental and simulation literature in materials science, hindering comparison and machine-actionable reuse. We present four domain-expert-reviewed JSON Schemas for ALD and ALE experimental and simulation processes. Curated with schema-miner and grounded in QUDT using schema-miner pro, the schemas structure materials, process conditions, configurations , and measured or predicted results. We compare their scope, structure, and semantic grounding, and demonstrate their use for schema-guided literature extraction and publication of structured records through ORKG templates.
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All authors Sameer Sadruddin, Eleni Poupaki, Alex Watkins, Bora Karasulu, Adriaan J. M. Mackus, Erwin Kessels, Sören Auer, Jennifer D'Souza

Soft Condensed Matter

Colloidal shadows reveal hidden solute transport

Haoyu Liu, Zehao Chen and Amir A. Pahlavan

An object releasing a chemical into a surrounding flow leaves behind a plume that encodes the rate of release, but for most solutes, that plume is invisible. Classical transport theory describes this configuration through a self-similar concentration boundary layer whose structure has never been resolved experimentally in forced flow at low Reynolds number: a century of measurements at these conditions has returned integrated transfer rates rather than the field itself. Here we show that both the field and the information it carries are experimentally accessible. Around hydrogel posts photopatterned inside a microfluidic channel, a released solute drives suspended colloidal particles away by diffusiophoresis, i.e., their drift along chemical gradients, carving a particle-free “shadow” downstream. Using a fluorescent solute, we resolve the concentration field around the post and recover the classical self-similar structure of convective mass transfer. For an invisible surfactant, the width of the shadow, benchmarked against a directly imaged solute on the same platform, then serves as a proxy for the dimensionless rate of mass transfer from the post. Finally, comparing two orientations of a triangular post tests a classical prediction by Brenner: the local concentration fields rearrange, yet no orientation dependence of the integrated transfer rate is resolved. For solute–tracer pairs whose diffusiophoretic response is known, colloidal shadows thus turn ordinary tracer particles into quantitative reporters of chemical exchange that cannot be observed directly.
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Quantum Gases

Topological chirality of dissipative limit cycles in an open Dicke model

Nikolay Yegovtsev, Sayan Choudhury and W. Vincent Liu

In an open, $U(1)$-symmetric Dicke model with chiral atom-cavity couplings, we show that dissipation drives two limit-cycle phases of opposite chirality in the thermodynamic limit, obtaining exact analytical solutions. These phases are separated by a $U(1)$-broken superradiant state, lending the phase diagram a topological character, and persist under $U(1)$-preserving perturbations, making them candidates for chiral continuous time crystals. In addition to stable normal and inverted steady states, the model also exhibits multistability, where the long-time dynamics is set by the initial state. Our results establish dissipation as a resource for inducing chiral dynamical order in light-matter coupled systems.
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Statistical Mechanics

Models and Measures of Statistical Physics and Sociophysics for Fracture Mechanics and Earthquake Dynamics: An Introduction

Sudip Sarkar, Soumyajyoti Biswas and Bikas K. Chakrabarti

The breaking or fracture of materials and damages or devastations due to earthquakes have caught our attention since the earliest stage of human civilization. In fact, at around 1500, Leonardo Da Vinci made the pioneering observation that, unlike elastic constants (formalized later by Hooke in 1678) of the materials, the tensile (breaking) strengths of nominally identical iron wires decrease drastically with their length, indicating the vanishing breaking strength of materials in the large size limit, suggesting the impossibility of constructing arbitrarily large structures. This was the first observation that unlike the elasticity of disordered materials, which remains defined in the thermodynamic limit (self averaging statistics), the breaking properties of the disordered materials have extreme (non self averaging) statistics. In spite of major and some precise developments in statistical physical modelling and characterizing the fracture mechanics (starting with Allan Griffith's crack nucleation theory in 1921 and the weakest link failure Fibre Bundle Model of Frederick Thomas Peirce in 1926) and of earthquake dynamics (starting with Robert Burridge and Leon Knopoff's continuum dynamical model in 1967 and later other discrete or lattice train models or fractal overlap models of stick slip earthquakes), no graduate level textbook in condensed matter physics or in statistical physics introduces the basic models and their properties. And now computer scientists and social scientists (coming with their social inequality measures applied to the avalanche statistics in precursor failures) are joining their efforts to explore the new precursory inequality measures for big avalanches or failures. This introductory review is designed to fill this gap with a view to introducing these to this wider audience and to take them to the current frontiers in these fields.
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Mesoscale and Nanoscale Physics

Orbital-geometric spin response: inter-band coherence versus orbital-to-spin conversion

Dimitrie Culcer

Orbitronics seeks to convert orbital angular momentum (OAM) into spin, but its microscopic dynamics is not understood. Here I show that, at moderate spin-orbit coupling, an electrically induced spin density contains a direct term and an orbital-geometric spin response (OGSR) due to inter-band coherence of the spinless parent Hamiltonian—related to OAM but not descended from it. In massive Dirac fermions the OGSR survives as the net OAM vanishes, and generates counterflow, opposing the direct response. These results provide guidelines for optimising orbitronic systems.
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