Materials Science
Discovery of a new weberite-type antiferroelectric: La3NbO7
Louis Alaerts, Jesse Schimpf, Xinyan Li et al. (+7 more)
Antiferroelectrics are antipolar materials which possess an electric field-induced phase transition to a polar, ferroelectric phase and offer significant potential for sensing/actuation and energy-storage applications. Known antiferroelectrics are relatively scarce and mainly based on a limited set of perovskite materials and their
alloys (e.g., PbZrO$_3$, AgNbO$_3$, NaNbO$_3$). Here, a new family of lead-free, weberite-type antiferroelectrics, identified through a large-scale, first-principles computational search is introduced. The screening methodology, which connects
lattice dynamics to antipolar distortions, predicted that La$_3$NbO$_7$ could exhibit antiferroelectricity. We confirm the prediction through the synthesis and characterization of epitaxial La$_3$NbO$_7$ thin films, which display the signature double hysteresis loops of an antiferroelectric material as well as clear evidence of an antipolar ground state structure from transmission electron microscopy. The antiferroelectricity in La$_3$NbO$_7$ is simpler than most known antiferroelectrics and can be explained by a Kittel-type mechanism involving the movement of niobium atoms in an oxygen octahedron through a single
phonon mode which results in a smaller change in the volume during the field-induced phase transition. Additionally, it is found that La$_3$NbO$_7$ combines a high threshold field with a high breakdown field ($\approx$ 6MV/cm) - which opens up opportunities for energy-storage applications. This new weberite-type family of materials offers many opportunities to tune electrical and temperature response especially through substitutions on the rare-earth site. Ultimately, this work demonstrates a successful data-driven theory-to-experiment discovery of an entirely new family of antiferroelectrics and provides a blueprint for the future design of ferroic materials.
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All authors Louis Alaerts, Jesse Schimpf, Xinyan Li, Jiongzhi Zheng, Ella Banyas, Jeffrey B. Neaton, Sinéad M. Griffin, Yimo Han, Lane W. Martin, Geoffroy Hautier
Strongly Correlated Electrons
Coupled sawtooth chain exchange network in olivine Mn$_2$GeO$_4$
Vincent C. Morano, Zeno Maesen, Stanislav Nikitin et al. (+6 more)
Sawtooth chain magnets have been a subject of historical interest in the field of frustrated magnetism, with classical olivine family $M_2TX_4$, ($M$ - 3d, $T$ - 4p, $X$ - chalcogen elements) typically realizing simple $\mathbf{k} = (000)$ states. The magnetism of the Mn$_2$GeO$_4$ olivine is surprisingly complex, proceeding from commensurate states to a multiferroic commensurate + incommensurate phase. Here we report inelastic
neutron scattering results from a Mn$_2$GeO$_4$ single
crystal and develop an effective
Hamiltonian including long-distance bilinear and dipolar interactions. The
magnetic interactions are predominantly
antiferromagnetic and span a three-dimensional exchange network consisting of coupled sawtooth chains. Based on the determined strength of the couplings, the dominant sawtooth chains appear at third- and fourth- rather than next-nearest-neighbor. However the next-nearest-neighbor interaction is, along with a modest Dzyaloshinskii-Moriya interaction, important for modeling the observed incommensurability. We use the best-fit
Hamiltonian as the basis for Langevin dynamics simulations and Luttinger-Tisza calculations of the high-temperature commensurate transition.
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All authors Vincent C. Morano, Zeno Maesen, Stanislav Nikitin, Jonathan S. White, Takashi Honda, Tsuyoshi Kimura, Michel Kenzelmann, Daniel Pajerowski, Oksana Zaharko
Statistical Mechanics · Cross-listed from quant-ph
Virtual temperatures as a key quantifier for passive states in quantum thermodynamic processes
Sachin Sonkar and Ramandeep S. Johal
We analyze the role of virtual temperatures for passive
quantum states through the lens of majorization theory. A mean temperature over the virtual temperatures of adjacent energy levels is defined to compare the passive states of the system resulting from isoenergetic and isoentropic transformations. The role of the minimum and the maximum (min-max) values of the virtual temperatures in determining the direction of heat flow between the system and the environment is argued based on majorization relations. We characterize the intermediate passive states in a
quantum Otto engine using these virtual temperatures and derive an upper bound for the Otto efficiency that can be expressed in terms of the min-max virtual temperatures of the working medium. An explicit example of the coupled-
spins system is worked out. Moreover, virtual temperatures serve to draw interesting parallels between the
quantum thermodynamic processes and their classical counterparts. Thus, virtual temperature emerges as a key operational quantity linking passivity and majorization to the optimal performance of
quantum thermal machines.
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Materials Science · Cross-listed from physics.comp-ph
A joint voxel flow-phase field framework for ultra-long microstructure evolution prediction with physical regularization
Ao Zhou, Salma Zahran, Chi Chen et al. (+2 more)
Phase-field (PF) modeling is a powerful tool for simulating microstructure
evolution. To accelerate the simulation of PF models governed by complex PDEs, machine learning methods such as PINNs and ConvLSTM have been introduced. However, current machine-learning-based approaches still suffer from limited flexibility, poor generalization, and short prediction horizons. To address these challenges, we present a joint framework that couples a voxel-flow network (VFN) with PF simulations in an alternating manner for long-horizon prediction of microstructure
evolution with substantial computational acceleration. The VFN iteratively predicts future
evolution by generating the next snapshot from the previous two snapshots. Periodic PF simulations suppress nonphysical artifacts, reduce accumulated error, and extend the reliable prediction horizon. The VFN was validated using a grain-growth example, and its accuracy outperforms that of similar prediction methods while preserving topological grain details. For an ultra-long grain-growth prediction of 82 frames from 2 input frames, the grain number decreases from 600 to 29 while the NMSE of the average grain area remains 1.64%. The framework also exhibits good generalizability across different PF models. Overall, this joint framework enables rapid, flexible, generalizable, and physically consistent microstructure
forecasting from image-based data over ultra-long time scales.
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All authors Ao Zhou, Salma Zahran, Chi Chen, Zhengyang Zhang, Yanming Wang
Statistical Mechanics · Cross-listed from physics.atom-ph
Symmetry-controlled thermal activation in pyramidal Coulomb clusters: Testing Kramers-Langer theory
Akhil Ayyadevara, Anand Prakash, Shovan Dutta et al. (+2 more)
Laser-cooled ions confined in electromagnetic traps provide a unique, tunable mesoscopic system where the interplay of the trapping potential, nonlinear Coulomb interactions, and
laser-ion scattering generates rich, collective dynamics. In this work, we engineer thermally activated switching between two oppositely oriented, square-pyramidal configurations of five
laser-cooled ions in a Paul trap. For identical ions ($^{40}\mathrm{Ca}^{+}$), the inversions proceed via a Berry pseudo-rotation mechanism with a low activation barrier, enabled by the permutation
symmetry, in contrast to the umbrella inversion observed in ammonia. The experimentally measured inversion rates, spanning two orders of magnitude, are accurately captured by the multidimensional Kramers-Langer theory, enabling thermometry of the Doppler-cooled ion cluster at $1.8 \pm 0.1$ mK. By substituting the apex ion with a heavier isotope ($^{44}\mathrm{Ca}^{+}$), we break the permutation
symmetry and observe a suppression of thermally activated inversions. Numerical analysis reveals that this
symmetry breaking closes the low-barrier channel, forcing the system to invert through a high-barrier turnstile rotation. Thus, we demonstrate a structural analogue of molecular kinetic isotope effects, establishing trapped ions as a versatile platform to explore
symmetry-controlled collective dynamics.
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All authors Akhil Ayyadevara, Anand Prakash, Shovan Dutta, Arun Paramekanti, S. A. Rangwala
Materials Science · Cross-listed from cs.AI
Higher-Order Knowledge Representations for Agentic Scientific Reasoning
Isabella A. Stewart and Markus J. Buehler
Scientific inquiry requires systems-level
reasoning that integrates heterogeneous experimental data, cross-domain knowledge, and mechanistic evidence into coherent explanations. While Large
Language Models (LLMs) offer inferential capabilities, they often depend on
retrieval-augmented contexts that lack structural depth. Traditional Knowledge Graphs (KGs) attempt to bridge this gap, yet their pairwise constraints fail to capture the irreducible higher-order interactions that govern emergent physical behavior. To address this, we introduce a methodology for constructing hypergraph-based knowledge representations that faithfully encode multi-entity relationships. Applied to a corpus of ~1,100 manuscripts on biocomposite scaffolds, our framework constructs a global hypergraph of 161,172 nodes and 320,201 hyperedges, revealing a scale-free
topology (power law exponent ~1.23) organized around highly connected conceptual hubs. This representation prevents the combinatorial explosion typical of pairwise expansions and explicitly preserves the co-occurrence context of scientific formulations. We further demonstrate that equipping agentic systems with hypergraph traversal tools, specifically using node-intersection constraints, enables them to bridge semantically distant concepts. By exploiting these higher-order pathways, the system successfully generates grounded mechanistic hypotheses for novel composite materials, such as linking cerium
oxide to PCL scaffolds via chitosan intermediates. This work establishes a "teacherless" agentic
reasoning system where hypergraph
topology acts as a verifiable guardrail, accelerating scientific discovery by uncovering relationships obscured by traditional graph methods.
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Quantum Gases
Half-vortex soliton lattices in spin-orbit-coupled Bose-Einstein condensates with a quasi-flat band
Chenhui Wang, Yongping Zhang and Vladimir V. Konotop
Periodic potentials with flat bands in their spectra support strongly localized nonlinear excitations. Although a perfectly flat band cannot exist in a continuous system, a
spin-orbit-coupled Bose-Einstein condensate loaded in a Zeeman
lattice can realize the quasi-flat lowest band with an extremely narrow bandwidth. In such a quasi flat band, half
vortex solitons become confined within a single
lattice cell, enabling the formation of arrays of coupled half
vortex solitons arranged of various spatial geometries. In this work, we study the existence and stability of these
lattices within the framework of the two-component Gross-Pitaevskii equation. We demonstrate that, near the quasi-flat band, half-
vortex solitons and their arrays can be excited with a nearly negligible number of atoms and are constrained by their local
symmetries, which are isomorphic to a dihedral group of order 8. This allows observation of the respective field patterns in the nearly linear regime where they exhibit enhanced stability. The constructed
lattices may have diverse
geometric profiles, and in particular create a composite super-half-
vortex soliton with nonlinear
symmetry breaking.
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Materials Science
Triple-well ferroelectricity and kagome-like Chern flat band in two-dimensional multiferroic CuVP$_2$Se$_6$
Brian Anchico, Jingyi Duan, Haojie Sun et al. (+3 more)
Two-dimensional multiferroics that host nontrivial topological bands offer a rich platform for correlated and tunable
quantum phenomena, yet such materials remain rare. Here, using first-principles calculations, we reveal that monolayer CuVP$_2$Se$_6$ unites a tunable triple-well ferroelectric transition with a
spin-polarized Chern flat band. The ferroelectric and paraelectric phases are close in energy and can be reversibly switched by moderate strain or an electric field. During the transition, a kagome-like flat band emerges near the
Fermi level, which we describe via a minimal three-orbital tight-binding model on a triangular
lattice. Furthermore, the system exhibits sizable
magnetic anisotropy and a magnetization-dependent Chern insulating state: the Chern number is $C = \pm 1$ for out-of-plane magnetization but becomes trivial when the moments rotate in-plane. These findings establish CuVP$_2$Se$_6$ as a promising candidate for exploring electrically tunable flat-band correlations and topological magnetism in a multiferroic monolayer.
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All authors Brian Anchico, Jingyi Duan, Haojie Sun, Minjun Wang, Mikhail Talanov, Wei Jiang
Soft Condensed Matter
Determining fluid-crystal phase boundaries for a binary hard-sphere mixture using direct-coexistence simulations
Rinske M. Alkemade, Alessandro Salo, Laura Filion et al. (+1 more)
Determining fluid-
crystal phase boundaries via direct-coexistence methods can be challenging due to the fact that the simulation box can introduce
crystal strain. Recently, a direct-coexistence approach was developed which allows one to easily identify the
equilibrium strain-free fluid-
crystal coexistence in monodisperse systems. Here, we show that this approach can be readily extended to binary mixtures forming stoichiometric binary
crystals, allowing accurate and efficient determination of the phase boundaries. Moreover, we examine how the choice of
crystal plane in contact with the fluid affects the accuracy of the phase boundary determination. The method is easy to implement and does not require prior knowledge of the binary fluid's equation of state. These results further establish the method as a robust and practical tool for accurately determining fluid-
crystal phase boundaries.
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All authors Rinske M. Alkemade, Alessandro Salo, Laura Filion, Frank Smallenburg
Materials Science
Lateral Graphene-Metallene Interfaces at the Nanoscale
Mohammad Bagheri and Pekka Koskinen
Metallenes are atomically thin, nonlayered two-dimensional materials. While they have appealing properties, their isotropic metallic bonding makes their stabilization difficult and presents considerable challenges to their synthesis and practical applications. However, their stabilization can still be achieved by suspending them in the pores of two-dimensional template materials, making the properties of lateral interfaces of metallenes scientifically relevant. Here, we combined density-functional theory and universal machine-learning interatomic potentials to study lateral interfaces between
graphene and 45 metallenes with various profiles. We optimized the interfaces and analyzed their energies, electronic structures, and stabilities at room temperature, defect formations, and structural deformations. While broad trends were identified using machine-learning analysis of all interfaces, density-functional theory was the main tool for studying the microscopic properties of selected elements. We found that the interfaces are the most stable energetically and with respect to
lattice mismatch, defect formation, and lateral strain when their profiles were geometrically smooth. The most stable interfaces are found for transition metals. In addition, we demonstrate how universal machine-learning interatomic potentials now offer the accuracy required for the modeling of
graphene-metallene interfaces. By systematically expanding the understanding of metallenes' interface properties, we hope these results guide and accelerate their synthesis to enable future applications and benefit from metallenes' appealing properties.
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Mesoscale and Nanoscale Physics
Floquet-driven tunneling control in monolayer MoS$_2$
Rachid El Aitouni, Aotmane En Naciri, Clarence Cortes et al. (+2 more)
We study how
fermions in molybdenum disulfide MoS$_2$ interact with a
laser field and a static potential barrier, focusing on the transmission probability. Our aim is to understand and control
photon-assisted
quantum transport in this two-dimensional material under external driving. We use the Floquet approximation to describe the wave functions in the three regions of the system. By applying continuity conditions at the boundaries, we obtain a set of equations involving an infinite number of Floquet modes. We explicitly determine transmissions involving the central band $E$ and the first sidebands $E \pm \hbar\omega$. As for higher-order bands, we use the transfer
matrix approach together with current density to compute the associated transmissions. Our results reveal that the transmission probability oscillates for both
spin-up and
spin-down electrons. The oscillations of
spin-down electrons occur over nearly twice the period of
spin-up electrons. Among all bands, the central one consistently shows the highest transmission. We also find that stronger
laser fields and wider barriers both lead to reduced transmission. Moreover,
laser irradiation enables controllable channeling and filtering of transmission bands by tuning the
laser intensity and system parameters. This highlights the potential of
laser-driven MoS$_2$ structures for highly sensitive electromagnetic sensors and advanced optoelectronic devices.
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All authors Rachid El Aitouni, Aotmane En Naciri, Clarence Cortes, David Laroze, Ahmed Jellal
Strongly Correlated Electrons
Affordable Five-Orbital Dynamical Mean-Field Theory for Layered Iridates and Rhodates
Léo Gaspard and Cyril Martins
Full $d$-
manifold DMFT with numerically exact solvers has remained computationally prohibitive for
spin-orbit materials due their scaling and severe sign problem, forcing the community to rely on simplified one- and three-band models that omit the $e_g$ states despite their proximity with the $t_{2g}$ orbitals. We present the first full five-orbital Dynamical Mean-Field Theory (DMFT) calculations including
spin-orbit coupling for the layered iridates and rhodates \bio~and \bro, revealing that the correlation effects shift significantly the $e_g$ states through static mean-field corrections rather than dynamical fluctuations. Motivated by this insight, we introduce hybrid-DMFT (hDMFT), which treats these orbitals and their coupling to the low-energy
manifold at the mean-field level while maintaining near quantitative accuracy at a drastically reduced computational cost. These calculation establish hDMFT as a practical and accurate method for full $d$-
manifold studies of layered iridates and rhodates, enabling systematic investigations of temperature, doping and pressure dependence that were previously computationally intractable.
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Superconductivity · Cross-listed from quant-ph
Noise tailoring for error mitigation and for diagnozing digital quantum computers
Thibault Scoquart, Hugo Perrin and Kyrylo Snizhko
Error mitigation (EM) methods are crucial for obtaining reliable results in the realm of noisy intermediate-scale
quantum (NISQ) computers, where noise significantly impacts output accuracy. Some EM protocols are particularly efficient for specific types of noise. Yet the noise in the actual hardware may not align with that. In this article, we introduce Noise Tailoring (NT) – an innovative strategy designed to modify the structure of the noise associated with two-
qubit gates through statistical sampling. We perform classical emulation of the protocol behavior and find that the NT+EM results can be up to 5 times more accurate than the results of EM alone for realistic Pauli noise acting on two-
qubit gates. At the same time, on actual IBM
quantum computers, the NT method falls victim to various small error sources beyond Markovian Pauli noise. We propose to use the NT method for characterizing such error sources on
quantum computers in order to inform hardware development.
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Materials Science
Electric-Field Modulated Optical Transitions in Monolayer CrI3 and Its Nanoribbons
Xianzhe Zhu, Pu Liu, Wence Ding et al. (+3 more)
The successful synthesis of few-layer CrI3 has opened new avenues for research in two-dimensional
magnetic materials. Owing to its simple
crystal structure and excellent physical properties, layered CrI3 has been extensively studied in magneto-optical effects,
excitons, tunneling transport, and novel
memory devices. However, the most current theoretical studies rely heavily on the first-principles calculations, and a general analytical theoretical framework, particularly for electric-field modulation and transport properties, is still lacking. In this work, using a 28-band tight-binding model combined with linear response theory, we systematically investigate the optoelectronic response for monolayer CrI3 and its nanoribbons. The results demonstrate that: (1) a vertical electric field can selectively close the band gap of one
spin channel while the other remains insulating, resulting a transition to an half-metallic state; (2) the electric field dynamically shifts the optical transition peaks, providing a theoretical basis for extracting band parameters from experimental photoconductivity spectra; (3) nanoribbons with different edge morphologies exhibit distinct edge-state distributions and electronic properties, indicating that optical transition can be dynamically modualted through edge design. The theoretical model developed in this study, which can describe external electric field effect, offers an efficient and flexible approach for analytically investigating the CrI3 family and related materials. This model overcomes the limitations of first-principles methods and provides a solid foundation for designing spintronic and optoelectronic devices controlled by electric fields and edge effect.
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All authors Xianzhe Zhu, Pu Liu, Wence Ding, Benhu Zhou, Xiaoying Zhou, Guanghui Zhou
Strongly Correlated Electrons
Switching magnetization of quantum antiferromagnets: Schwinger boson mean-field theory compared to exact diagonalization
Florian Johannesmann, Asliddin Khudoyberdiev and Götz S. Uhrig
Antiferromagnets have attracted significant
attention because of their considerable potential in engineering high-density and ultrafast
memory devices, a crucial and increasingly demanded component of contemporary high-performance information technology. Theoretical and experimental investigations are actively progressing to provide the capability of efficient switching and precise control of the Néel vector, which is crucial for the intended practical applications of antiferromagnets. Recently, a time-dependent Schwinger
boson mean-field theory has been successfully developed to study the sublattice magnetization switching in anisotropic
quantum antiferromagnets [K. Bolsmann $et \, al.$, \textcolor{blue}{\hyperlink{10.1103/PRXQuantum.4.030332}{PRX
Quantum $\mathbf{4}$, 030332 (2023)}}]. Here we use a complementary exact diagonalization method to study such sublattice magnetization switching, but in small-cluster
quantum antiferromagnets, by means of an external
magnetic field. Furthermore, this article aims to support the findings of the Schwinger
boson approach. We show that the results of both approaches are consistent at short time scales, with only about 12.5 $\%$ deviations. The consistency of the outcomes obtained through this alternative exact approach demonstrates that the time-dependent Schwinger
boson mean-field theory is a versatile framework to capture the essentials of the switching process in
quantum antiferromagnets. Thereby, the findings of current article pave the way for further theoretical and computational progress in the study of antiferromagnets for engineering spintronic devices with ultrahigh density and ultrafast speed.
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Mesoscale and Nanoscale Physics
Intrinsic Gyrotropic Magnetic Current of Orbital Origin
Koushik Ghorai, Sankar Sarkar and Amit Agarwal
In gyrotropic
crystals, an oscillating
magnetic field induces a charge response known as the gyrotropic
magnetic current. While its conventional origin is attributed to
magnetic field modified band energy and shift in the
Fermi-surface, a recent study identified an additional
spin-driven
magnetic displacement contribution. Here, we complete the picture by identifying the orbital counterpart of the
magnetic displacement current. Using a density-
matrix formulation that incorporates both minimal coupling and
spin-Zeeman interactions, we derive the electronic equations of motion in the presence of an oscillating
magnetic field and uncover a previously unexplored orbital contribution to the wavepacket velocity. Physically, this contribution arises from the time variation of the
magnetic-field induced charge polarization. In the low frequency transport regime, this mechanism becomes purely intrinsic. We illustrate this intrinsic gyrotropic current of orbital origin in the ${\cal P}{\cal T}$-symmetric antiferromagnet CuMnAs. We show that the intrinsic gyrotropic
magnetic current reverses sign upon Néel vector reversal, establishing it as a direct probe of
antiferromagnetic order in CuMnAs and other $\mathcal{PT}$-symmetric antiferromagnets.
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Mesoscale and Nanoscale Physics
Single-enantiomer spin polarisers in superconducting junctions
Lorenz Meyer, Nicolas Néel and Jörg Kröger
Chiral matter acting as a
spin-selective device in biased electron transport is attracting
attention for the
quantum-technological design of miniaturized electronics. To date, however, experimental reports on
spin selectivity are not conclusive. The magnetoresistance in electron transport measurements observed for
chiral materials on ferromagnets upon magnetisation reversal is proposed to result from electrostatic rather than from the sought-after
chiral effects. Recent break junction studies even question the
spin-dependent electron flow across single
chiral molecules. Here, we avoid
ferromagnetic electrodes and magnetisation reversal to provide unambiguous experimental evidence for the chirality-induced
spin selectivity effect of single enantiomers. Functionalising the superconducting tip of a scanning tunnelling microscope with a manganese atom cluster gives rise to Yu-Shiba-Rusinov resonances that serve as
spin-sensitive probes of the tunnelling current in junctions of single heptahelicene molecules adsorbed on a crystalline lead surface. Our key finding is the dependence of the signal strength of these states in spectroscopy of the differential conductance on the handedness of the molecule. The experiments unveil the role of the enantiomers as
spin polarisers and the irrelevance of electrostatics in the chosen model system.
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Materials Science
Tuning Excitonic Properties and Charge Carrier Dynamics by Halide Alloying in Cs3Bi2(Br1-xIx)9 semiconductors
He Zhao and Eline M. Hutter
The perovskite-inspired bismuth halide
semiconductor Cs3Bi2Br9 is widely investigated as photoactive material for light-conversion applications. However, charge generation and separation are inherently limited by its modest sunlight absorption and strong
exciton binding energy, respectively. Here, we demonstrate that both the light absorption and
exciton dissociation are improved by controlled substitution of Br with I via mechanochemical synthesis of Cs3Bi2(Br1-xIx)9. X-ray diffraction and Raman analyses confirm atomic-level halide mixing and reveal a crystallographic phase transition near x = 0.8. From absorption measurements on thin films, we determine the absorption coefficient, Urbach tail, and
exciton binding energy for several Cs3Bi2(Br1-xIx)9 compositions. From here, we find that the band gap can be tuned from 2.59 to 1.93 eV (for x = 0.9), while
exciton binding energies reach a minimum at x = 0.6. Finally, transient absorption spectroscopy measurements suggest a weak correlation between recombination lifetime and Urbach energy, where the longest lifetimes are observed for the materials with lowest disorder. These results offer valuable insights for designing stable bismuth halide
semiconductors with favorable light absorption properties and charge carrier dynamics.
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Materials Science
Berry Phase of Bloch States through Modular Symmetries
Emanuele Maggio
The theoretical identification of crystalline topological materials has enjoyed sustained success in simplified materials models, often by singling out discrete
symmetry operations protecting the topological phase. When band structure calculations of realistic materials are considered, complications often arise owing to the requirement of a consistent gauge in the Brillouin zone, or down to the fineness of its sampling. Yet, the Berry phase, acting as topological label, encodes geometrical properties of the system, and it should be easily accessible. Here, an expression for the Berry phase is obtained, thanks to analytical Bloch states constructed from an infinite series of $s$-type Gaussian orbitals. Two contributions in the Berry phase are identified, with one having an immediate
geometric interpretation, being equal to the Zak phase.
Eigenvalues of a modular
symmetry, considered here for the first time in the context of crystalline solid state systems, are put in correspondence with the Zak phase: modular
symmetries allow to define a non-trivial action for the spatial inversion also when the system does not have an inversion centre, as for the considered case of space group no. 22 ($F222$), which is known to host
symmetry equivalent Bloch states distinguishable by their Berry phase.
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Soft Condensed Matter
Mechanisms of Spatiotemporal Damage Evolution in Double Polymer Networks
Magali Le Goff, Laureano Ortellado, Jiting Tian et al. (+3 more)
Double
polymer networks exhibit a striking enhancement of toughness compared to single networks, yet the microscopic mechanisms governing stress redistribution, damage
evolution, and fracture remain incompletely understood. Using large-scale coarse-grained molecular dynamics simulations under uniaxial deformation, we resolve bond scission statistics, local stress redistribution following individual bond-breaking events, and the spatiotemporal
evolution of damage in single- and double-network architectures. We show that while the early mechanical response is dominated by the pre-stretched sacrificial network, damage
evolution in double networks follows a qualitatively distinct pathway. In contrast to single networks, where anisotropic stress redistribution promotes rapid localization and catastrophic fracture, the presence of a soft
matrix in double networks induces a screening of stress redistribution generated by sacrificial bond scission. This screening suppresses correlated rupture events and stabilizes multiple damage zones, leading to a strongly delocalized damage landscape over a broad deformation range. At larger strains, when the
matrix becomes load-bearing, damage progressively localizes, ultimately triggering fracture. By isolating the dynamics of individual damage zones, we further demonstrate that
matrix-mediated stress screening stabilizes defects and delays localization. Together, these results identify stress-screening-induced damage delocalization as a central microscopic mechanism underlying toughness enhancement in multiple-network elastomers.
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All authors Magali Le Goff, Laureano Ortellado, Jiting Tian, Mehdi Bouzid, Jean-Louis Barrat, Kirsten Martens
Materials Science
Scalable Dielectric Tensor Predictions for Inorganic Materials using Equivariant Graph Neural Networks
Haowei Hua, Chen Liang, Ding Pan et al. (+4 more)
Accurate prediction of dielectric tensors is essential for accelerating the discovery of next-generation inorganic dielectric materials. Existing machine learning approaches, such as equivariant graph neural networks, typically rely on specially-designed network architectures to enforce O(3) equivariance. However, to preserve equivariance, these specially-designed models restrict the update of equivariant features during message passing to linear transformations or gated equivariant nonlinearities. The inability to implicitly characterize more complex nonlinear structures may reduce the predictive accuracy of the model. In this study, we introduce a frame-averaging-based approach to achieve equivariant dielectric tensor prediction. We propose GoeCTP, an O(3)-equivariant framework that predicts dielectric tensors without imposing any structural restrictions on the backbone network. We
benchmark its performance against several state-of-the-art models and further employ it for large-scale virtual screening of thermodynamically stable materials from the Materials Project database. GoeCTP successfully identifies various promising candidates, such as Zr(InBr$_3$)$_2$ (band gap $E_g = 2.41$ eV, dielectric constant $\overline{\varepsilon} = 194.72$) and SeI$_2$ (anisotropy ratio $\alpha_r = 96.763$), demonstrating its accuracy and efficiency in accelerating the discovery of advanced inorganic dielectric materials.
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All authors Haowei Hua, Chen Liang, Ding Pan, Irwin King, Shengchao Liu, Koji Tsuda, Wanyu Lin
Quantum Gases
Topological sensing of superfluid rotation using non-Hermitian optical dimers
Aritra Ghosh, Nilamoni Daloi and M. Bhattacharya
We theoretically investigate a non-Hermitian optical dimer whose parameters are renormalized by dispersive and dissipative backaction from the coupling of the passive cavity with a ring-trapped Bose-Einstein condensate. The passive cavity is driven by a two-tone control
laser, where each tone is in a coherent superposition of Laguerre-Gaussian beams carrying orbital angular momenta $\pm \ell \hbar$. This imprints an optical
lattice on the ring trap, leading to Bragg-diffracted sidemode excitations. Using an exact Schur-complement reduction of the full light-matter dynamics, we derive a frequency-dependent self-energy and identify a static regime in which the atomic response produces a complex shift of the passive optical mode. This renormalized dimer supports a tunable exceptional point, enabling spectroscopic signatures in the optical transmission due to a probe field, which can in turn be utilized for estimating the winding number of the persistent current. Exploiting the associated half-integer topological charge, we propose a digital exceptional-point-based sensing scheme based on eigenmode permutation, providing a noise-resilient method to sense superfluid rotation without relying on fragile
eigenvalue splittings. Importantly, the sensing proposals are intrinsically nondestructive, preserving the coherence of the atomic superfluid.
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Soft Condensed Matter
Decoupling Structure and Elasticity in Colloidal Gels Under Isotropic Compression
M. Milani, E. Cavalletti, V. Ruzzi et al. (+6 more)
We exploit the controlled drying of millimeter-sized gel beads to investigate isotropic compression of colloidal fractal gels. Using a custom dynamic light scattering setup, we demonstrate that stresses imposed by drying on the bead surface propagate homogeneously throughout the gel volume, inducing plastic rearrangements. We find that the Young modulus and yield stress of the gels increase monotonically with the instantaneous colloid volume fraction, $\phi$, exhibiting a mechanical response that depends solely on $\phi$, regardless of the drying history. In striking contrast, small-angle X-ray scattering reveals that the gel microstructure retains a strong
memory of its initial state, depending on both $\varphi$ and the entire compression pathway. Our findings challenge the prevailing paradigm of a one-to-one relationship between microstructure and elasticity in colloidal fractal gels, opening new avenues for independent control over the structural and mechanical properties of soft materials.
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All authors M. Milani, E. Cavalletti, V. Ruzzi, A. Martinelli, P. Dieudonne-George, C. Ligoure, T. Phou, L. Cipelletti, L. Ramos
Strongly Correlated Electrons
Probing quantum critical crossover via impurity renormalization group
Tao Yang, Z. Y. Xie, Rui Wang et al. (+1 more)
Quantum impurities can host exotic many-body states that serve as sensitive probes of bath correlations. However, quantitative and non-perturbative methods for determining
impurity thermodynamics in such settings remain scarce. Here, we introduce an
impurity renormalization group approach that merges the tensor-network representation with the numerical renormalization group cutoff scheme. This method overcomes conventional limitations by treating bath correlations and
impurity interactions on an equal footing. Applying our approach to the finite-temperature
quantum critical regime of
quantum spin systems, we uncover striking
impurity-induced phenomena. In a coupled Heisenberg ladder, the
impurity triggers a fractionalization of the local
magnetic moment. Moreover, the derivative of the
impurity susceptibility develops cusps that mark the crossover into the
quantum critical regime. We also observe an exotic
evolution of the
spin correlation function driven by the interplay between bath correlations and the
impurity. Our results demonstrate that this method can efficiently solve correlated systems with defects, opening new pathways to discovering novel
impurity physics beyond those in non-interacting thermal baths.
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All authors Tao Yang, Z. Y. Xie, Rui Wang, Baigeng Wang
Materials Science
Towards understanding the defect properties in the multivalent A-site Na$_{0.5}$Bi$_{0.5}$TiO$_3$-based perovskite ceramics
Pengcheng Hu, Chinmay Chandan Parhi, Jurij Koruza et al. (+1 more)
A defect model involving cation and anion vacancies and anti-site defects is proposed that accounts for the non-stoichiometry of multi-valent $A$-site Na$_{0.5}$Bi$_{0.5}$TiO$_3$ based perovskite
oxides with $ABO_3$ composition. A series of samples with varying $A$-site non-stoichiometry and $A$:$B$ ratios were prepared to investigate their electrical conductivity. The oxygen partial pressure and temperature dependent conductivities where studied with direct current (dc) and alternating current (ac) techniques, enabling to separate between ionic and electronic conduction. The Na-excess samples, regardless of the $A$:$B$ ratio, exhibit dominant ionic conductivity and $p$-type electronic conduction, with the highest total conductivity reaching $4 \times 10^{-4}$ S/cm at 450$^\circ$C. In contrast, the Bi-excess samples display more insulating characteristics and $n$-type electronic conductivity, with conductivity values within the 10$^{-8}$ S/cm range at 450$^\circ$C. These conductivity results strongly support the proposed defect model, which offers a straightforward description of defect chemistry in NBT-based ceramics and serves as a valuable guide for optimizing sample processing to achieve tailored properties.
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All authors Pengcheng Hu, Chinmay Chandan Parhi, Jurij Koruza, Andreas Klein
Materials Science
Nanoscale resistive switching in electrodeposited MOF Prussian blue analogs driven by K-ion intercalation probed by C-AFM
L. B. Avila, O. de Leuze, M. Pohlitz et al. (+12 more)
K-ion intercalation in Prussian blue analogs (PBAs) is a well-established charge storage mechanism in potassium-ion batteries; here, we demonstrate that this same ion intercalation process is the basis for nanoscale resistive switching behavior in PBA-base memristive devices. Using C-AFM, we directly visualize and electrically control this intercalation process within sub-100 nm volumes, revealing reversible, localized conductance modulation driven by K-ion intercalation and Fe^(2+)/Fe^(3+) redox reconfiguration. This nanoscale operability highlights the exceptional potential of PBAs for high-scalable and low-dimension memristor-based devices integration. Due to their modular composition, PBAs constitute a chemically rich, earth-abundant materials platform whose electronic and ionic properties can be precisely tuned for specific device functions. K-ion intercalation PBA-based memristor devices, with their single-step, aqueous, and room-temperature fabrication, enable low-cost, large-scale processing compatible with CMOS, without any additional post-fabrication processing. Our findings establish PBAs as a new class of intercalation memristors with scalable nanoscale switching and exceptional materials versatility, toward highly integrated neuromorphic and non-volatile
memory technologies. This work provides the first demonstration of intercalation-driven resistive switching under ultrafast voltage sweeps, with PW operating up to 200 V/s and PB up to 50 V/s. This unprecedented speed establishes PBAs as a distinct, high-rate class of K-ion intercalation memristors suitable for fast, high-density neuromorphic and
memory applications.
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All authors L. B. Avila, O. de Leuze, M. Pohlitz, M. A Villena, Ramon Torres-Cavanillas, C. Ducarme, A. Lopes Temporao, T. G. Coppée, A. Moureaux, S. Arib, Eugenio Coronado, C. K. Müller, J. B. Roldán, B. Hackens, F. Abreu Araujo
Materials Science
How semiconducting are ferroelectrics: The fundamental, optical and transport gaps of Na$_{0.5}$Bi$_{0.5}$TiO$_3$-BaTiO$_3$ and NaNbO$_{3}$
Pengcheng Hu, Nicole Bein, Chinmay Chandan Parhi et al. (+7 more)
The energy gap is a fundamental property of materials, directly related to their optical and electronic properties. The energy gap of ferroelectric compounds and its adjustment by compositional variation has particularly attracted
attention in recent years due to potential application in energy conversion and/or catalytic devices. It is demonstrated that it is necessary to distinguish between the fundamental gap, $E_{\rm g}^{0}$, the optical gap, $E_{\rm g}^{\rm opt}$, and the transport gap, $E_{\rm g}^{\rm tr}$, of ferroelectrics, which can differ significantly. The situation is comparable to those in organic
semiconductors and emerges from the presence of localized charges. The fundamental gap is a ground state property, i.e.\ the energy difference between the maximum of the fully occupied valence band and the minimum of the completely empty conduction band. In contrast, the optical and transport gaps are excited state properties involving localized (polaronic) electrons and/or holes at energies considerably different from the band edges. This work illustrates how the different energy gaps of ferroelectrics can be determined by combining optical measurements, X-ray photoelectron spectroscopy and temperature and oxygen partial pressure dependent electrical conductivity measurements. We determine fundamental gaps of $\approx 4.5\,$eV for both materials, optical gaps of $3.25-3.45\,$eV/$3.5\,$eV and electrical gaps of $\approx 1.4\,$eV/$3.3\,$eV for Na$_{0.5}$Bi$_{0.5}$TiO$_3$-BaTiO$_3$/NaNbO$_{3}$, respectively.
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All authors Pengcheng Hu, Nicole Bein, Chinmay Chandan Parhi, Tadej Rojac, Barbara Malič, Mohammad Amirabbasi, Anton Volodin, Karsten Albe, Jurij Koruza, Andreas Klein
Superconductivity
Multigap nodeless superconductivity in Dirac semimetal PdTe
Fengrui Shi, Weilong Qiu, Chufan Chen et al. (+12 more)
PdTe has recently been reported to be a type-II Dirac semimetal while a bulk nodal and surface nodeless superconductivity (SC) has been claimed to coexist. In this work, we applied point-contact spectroscopy (PCS) method to systematically study the superconducting gap in PdTe single
crystals with a SC transition temperature $T_{c}=4.3$ K. The obtained differential conductance curves show a common deviation from a single-gap superconducting behavior and can be better fitted by a two-gap Blonder-Tinkham-Klapwijk model, suggesting the larger gap $\Delta_{L}$ with $2\Delta_{L}$=3.7 $k_{B}T_{c}$ and the smaller gap $\Delta_S$ yielding $2\Delta_{S}$=1.1-2.2 $k_{B}T_{c}$ with a weak interband scattering. The variations of conductance spectra among different contacts are proposed to be caused by the anisotropy of
Fermi surface
topology associated with different gaps.
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All authors Fengrui Shi, Weilong Qiu, Chufan Chen, Chunqiang Xu, Yan Zhang, Hao Zheng, Yuwei Zhou, Dongting Zhang, Mengwei Xie, Huiqiu Yuan, Shiyan Li, Yang Liu, Chao Cao, Xiaofeng Xu, Xin Lu
Disordered Systems and Neural Networks
Chaos in high-dimensional dynamical systems with tunable non-reciprocity
Samantha Fournier and Pierfrancesco Urbani
High-dimensional dynamical systems of interacting degrees of freedom are ubiquitous in the study of complex systems. When the directed interactions are totally uncorrelated, sufficiently strong and non-linear, many of these systems exhibit a chaotic attractor characterized by a positive maximal Lyapunov exponent (MLE). On the contrary, when the interactions are completely symmetric, the dynamics takes the form of a gradient descent on a carefully defined cost function, and it exhibits slow dynamics and aging. In this work, we consider the intermediate case in which the interactions are partially symmetric, with a parameter {\alpha} tuning the degree of non-reciprocity. We show that for any value of {\alpha} for which the corresponding system has non-reciprocal interactions, the dynamics lands on a chaotic attractor. Correspondingly, the MLE is a non-monotonous function of the degree of non-reciprocity. This implies that conservative forcing deriving from the gradient field of a rough energy landscape can make the system more chaotic.
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Quantum Gases
Scattering of a weakly bound dimer from a hard wall in one dimension
Xican Zhang and Shina Tan
We consider a dimer formed by two particles with an attractive contact interaction in one dimension, colliding with a hard wall. We compute the scattering phase shifts and the reflection coefficients for various collision energies and various mass ratios of the two particles. For low-energy collisions (with dimer kinetic energies much smaller than the binding energy) our results are consistent with those of D. Lee and M. Pine, The European Physical Journal A 47, 41 (2011). For mass ratios much greater than 1 we use the Born-Oppenheimer approximation to show that the scattering length and the effective range of the dimer-wall collision both depend logarithmically on the mass ratio. For collision energies much greater than the binding energy, the dissociation probability is inversely proportional to the square of the incident momentum of the dimer and we find the constant of proportionality analytically, and we use a semiclassical analysis to approximately derive the “angular distribution" of the dissociated pair, where the “angle" $\theta$ depends on the ratio of the velocities of the two outgoing unbound particles.
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