CMP Journal 2025-01-09
Statistics
Nature Physics: 2
arXiv: 50
Nature Physics
Controlling few-body reaction pathways using a Feshbach resonance
Original Paper | Atomic and molecular collision processes | 2025-01-08 19:00 EST
Shinsuke Haze, Jing-Lun Li, Dominik Dorer, José P. D'Incao, Paul S. Julienne, Eberhard Tiemann, Markus Deiß, Johannes Hecker Denschlag
Gaining control over chemical reactions at the quantum level is a central goal of cold and ultracold chemistry. Here we demonstrate a method for coherently steering the reaction flux across different product spin channels for a three-body recombination process in a cloud of trapped cold atoms. We use a magnetically tunable Feshbach resonance to admix, in a controlled way, a specific spin state to the reacting collision complex. This allows us to control the reaction flux into the admixed spin channel, which can be used to alter the reaction products. We also investigate the influence of an Efimov resonance on the reaction dynamics, observing a global enhancement of three-body recombination without favouring particular reaction channels. Our control scheme can be extended to other reaction processes and could be combined with other methods, such as quantum interference of reaction paths, to achieve further tuning capabilities of few-body reactions.
Atomic and molecular collision processes, Chemistry, Ultracold gases
Thermally driven quantum refrigerator autonomously resets a superconducting qubit
Original Paper | Quantum information | 2025-01-08 19:00 EST
Mohammed Ali Aamir, Paul Jamet Suria, José Antonio Marín Guzmán, Claudia Castillo-Moreno, Jeffrey M. Epstein, Nicole Yunger Halpern, Simone Gasparinetti
Although classical thermal machines power industries and modern living, quantum thermal engines have yet to prove their utility. Here, we demonstrate a useful quantum absorption refrigerator formed from superconducting circuits. We use it to cool a transmon qubit to a temperature lower than that achievable with any one available bath, thereby resetting the qubit to an initial state suitable for quantum computing. The process is driven by a thermal gradient and is autonomous, requiring no external feedback. The refrigerator exploits an engineered three-body interaction between the target qubit and two auxiliary qudits. Each auxiliary qudit is coupled to a physical heat bath, realized with a microwave waveguide populated with synthesized quasithermal radiation. If the target qubit is initially fully excited, its effective temperature reaches a steady-state level of approximately 22 mK, lower than what can be achieved by existing state-of-the-art reset protocols. Our results demonstrate that superconducting circuits with propagating thermal fields can be used to experimentally explore quantum thermodynamics and apply it to quantum information-processing tasks.
Quantum information, Single photons and quantum effects, Thermodynamics
arXiv
Hermitian and Non-Hermitian Topological Transitions Characterized by Manifold Distance
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
ZhaoXiang Fang, Ming Gong, Guang-Can Guo, Yongxu Fu, Long Xiong
Topological phases are generally characterized by topological invariants denoted by integer numbers. However, different topological systems often require different topological invariants to measure, and theses definition usually fail at critical points. Therefore, it's challenging to predict what would occur during the transformation between two different topological phases. To address these issues, we propose a general definition based on fidelity and trace distance from quantum information theory: manifold distance (MD). This definition does not rely on the berry connection but rather on the information of the two manifolds - their ground state wave functions. Thus, it can measure different topological systems (including traditional band topology models, non-Hermitian systems, and gapless systems, etc.) and exhibit some universal laws during the transformation between two topological phases. Our research demonstrates for different topological manifolds, the change rate (first-order derivative) or susceptibility (second-order derivative) of MD exhibit various divergent behaviors near the critical points. Compared to the strange correlator, which could be used as a diagnosis for short-range entangled states in 1D and 2D, MD is more universal and could be applied to non-Hermitian systems and long-range entangled states. For subsequent studies, we expect the method to be generalized to real-space or non-lattice models, in order to facilitate the study of a wider range of physical platforms such as open systems and many-body localization.
Strongly Correlated Electrons (cond-mat.str-el), Quantum Physics (quant-ph)
arXiv admin note: substantial text overlap with arXiv:2405.03323
Electromechanical Coupling Coefficient: New Approach to Study Auxetic Piezoelectric Harvesters
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Grégoire Forges (SYMME, IMS), David Gibus (SYMME), Adrien Morel (SYMME), Adrien Badel (SYMME), Héléne Debéda (IMS)
This work introduces a novel methodology to assess the performance of Piezoelectric Energy Harvesters (PEHs) in order to study auxetic enhancement possibilities. For this purpose, a new approach for evaluating the intrinsic effective Electromechanical Coupling Coefficient (EMCC) of piezoelectric layers is presented. As the current assessment methods are questioned under resonance exposures, theoretical models are presented to suggest what characteristics the harvested power will depend on. A two axis graph is introduced to enable the comparison of different PEHs. The method is finally applied to PEHs with different types of substrates: filled, hollow and auxetic. First results show that, generally, auxetic structures might not increase the intrinsic EMCC but only improve the elastic energy ratio in the piezoelectric layers.
Materials Science (cond-mat.mtrl-sci), Applied Physics (physics.app-ph), Classical Physics (physics.class-ph)
2024 IEEE 23rd International Conference on Micro and Miniature Power Systems, Self-Powered Sensors and Energy Autonomous Devices (PowerMEMS), University of South-Eastern Norway, NORWAY, Nov 2024, Tonsberg, Norway. pp.14-17
A novel BPS bound with a first order BPS system in the \(2D\) Gross-Pitaevskii equation
New Submission | Quantum Gases (cond-mat.quant-gas) | 2025-01-09 20:00 EST
A novel BPS bound for the Gross-Pitaevskii equations in two spatial
dimensions is presented. The energy can be bound from below in terms of
the combination of two boundary terms, one related to the vorticity (but
dressed'' by the condensate profile) and the second to theskewness''
of the configurations. The bound is saturated by configurations which
satisfy a system of two first-order PDE: when such BPS system is
satisfied, the Gross-Pitaevskii equations are satisfied as well. The
analytic solutions of this BPS system constructed in the present
manuscript represent configurations with fractional vorticity living in
an annulus. Using these techniques, we present the first analytic
examples of this kind. The hydrodynamical interpretation of the BPS
system is discussed. The implications of these results are outlined.
Quantum Gases (cond-mat.quant-gas), High Energy Physics - Phenomenology (hep-ph), High Energy Physics - Theory (hep-th), Exactly Solvable and Integrable Systems (nlin.SI), Nuclear Theory (nucl-th)
18 pages, 4 Figures
Nonlinear phononics in Bi\(_2\)Te\(_3\) from first-principles
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
A. Levchuk, R. Busselez, G. Vaudel, P. Ruello, V. Juvé, B. Arnaud
Density Functional Theory (DFT) calculations not only allow to predict the vibrational and optical properties of solids but also to understand and disentangle the mechanisms playing a key role in the generation of coherent optical phonons. Recent experiments performed on a Bi\(_2\)Te\(_3\) nanofilm have shown that a THz pulse launches at least a coherent \(A_{1g}^1\) phonon as the transient transmittance measured using an isotropic detection scheme displays oscillations with a frequency matching the frequency of the \(A_{1g}^1\) mode measured in Raman experiments. Such an observation can be explained by invoking either a sum frequency process or cubic/quartic phonon-phonon couplings as considered for Bi\(_2\)Se\(_3\), a parent compound of Bi\(_2\)Te\(_3\). By resorting to group theory and calculating energy surfaces from first-principles, the main phonon-phonon couplings can be identified. Furthermore, a minimal model can be built to compute the dynamics of the Raman active modes coupled to the infrared active mode driven by the experimental THz pulse. Our model firmly establishes that cubic phonon-phonon interactions are relevant as the agreement between the computed and experimental transmittance is noteworthy.
Materials Science (cond-mat.mtrl-sci)
6 pages, 3 figures, submitted to Physical Review Letters
Capturing spin-torque effects with a semilocal exchange-correlation functional
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Marie-Therese Huebsch, Fabien Tran, Martijn Marsman
We cure the lack of spin torque in semilocal exchange-correlation (XC) functionals by treating XC effects in the framework of spin-current-density-functional theory (SCDFT), and present the implementation of the first kind of this novel family of XC functionals in the Vienna ab-initio simulation package (VASP): An SCDFT functional featuring a U(1)\(\times\)SU(2) gauge-invariant \(2\times 2\) XC potential. While the framework can be applied to other XC functionals, the presented flavor of the SCDFT functional is based on Becke-Roussel exchange and Colle-Salvetti correlation. In addition to the \(2\times 2\) spin density and kinetic-energy density, the XC functional depends on the \(2\times 2\) spin-current density. The implementation requires the computation of the spin-current density within the projector-augmented-wave method and the variation of the XC energy with respect to it. The application to a Cr\(_3\) molecule and bulk MnO reveals (i) spin torque of the same order as obtained by methods including exact exchange, (ii) a counterintuitive contribution to the energy even in collinear ferromagnetic systems without spin-orbit coupling due to the gradient of the magnetization, and (iii) a similar computational cost per electronic step as calculations that depend on, inter alia, the kinetic-energy density, but convergence within fewer electronic steps.
Materials Science (cond-mat.mtrl-sci)
14 pages, 3 figures
Exploiting Instabilities to Enable Large Shape Transformations in Dielectric Elastomers
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Daniel Katusele, Carmel Majidi, Pradeep Sharma, Kaushik Dayal
Dielectric elastomers have significant potential for new technologies ranging from soft robots to biomedical devices, driven by their ability to display complex shape changes in response to electrical stimulus. However, an important shortcoming of current realizations is that large voltages are required for useful actuation strains. This work proposes, and demonstrates through theory and numerical simulations, a strategy to achieve large and controlled actuation by exploiting the electromechanical analog of the Treloar-Kearsley (TK) instability. The key idea is to use the fact that the TK instability is a symmetry-breaking bifurcation, which implies the existence of a symmetry-driven constant-energy region in the energy landscape. This provides for nonlinear soft modes with large deformations that can be accessed with very small external stimulus, which is achieved here by applying a small in-plane electric field. First, the bifurcation and post-bifurcation behavior of the electromechanical TK instability are established theoretically in the idealized setting of uniform deformation and electric field. Next, building on this, a finite element analysis of a realistic geometry with patterned top and bottom electrodes is applied to demonstrate large and soft shape changes driven by small voltage differences across the electrodes.
Soft Condensed Matter (cond-mat.soft)
Physical Review Applied, 23:014007, 2025
Quantum Electrodynamics of graphene Landau levels in a deep-subwavelength hyperbolic phonon polariton cavity
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Gian Marcello Andolina, Matteo Ceccanti, Bianca Turini, Riccardo Riolo, Marco Polini, Marco Schiró, Frank H.L. Koppens
The confinement of electromagnetic radiation within extremely small volumes offers an effective means to significantly enhance light-matter interactions, to the extent that zero-point quantum vacuum fluctuations can influence and control the properties of materials. Here, we develop a theoretical framework for the quantum electrodynamics of graphene Landau levels embedded in a deep subwavelength hyperbolic cavity, where light is confined into ultrasmall mode volumes. By studying the spectrum, we discuss the emergence of polaritons, and disentangle the contributions of resonant quantum vacuum effects from those of purely electrostatic interactions. Finally, we study the hybridization between magnetoplasmons and the cavity's electromagnetic modes.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
22 pages
Machine Learning for Identifying Grain Boundaries in Scanning Electron Microscopy (SEM) Images of Nanoparticle Superlattices
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Aanish Paruchuri, Carl Thrasher, A. J. Hart, Robert Macfarlane, Arthi Jayaraman
Nanoparticle superlattices consisting of ordered arrangements of nanoparticles exhibit unique optical, magnetic, and electronic properties arising from nanoparticle characteristics as well as their collective behaviors. Understanding how processing conditions influence the nanoscale arrangement and microstructure is critical for engineering materials with desired macroscopic properties. Microstructural features such as grain boundaries, lattice defects, and pores significantly affect these properties but are challenging to quantify using traditional manual analyses as they are labor-intensive and prone to errors. In this work, we present a machine learning workflow for automating grain segmentation in scanning electron microscopy (SEM) images of nanoparticle superlattices. This workflow integrates signal processing techniques, such as Radon transforms, with unsupervised learning methods like agglomerative hierarchical clustering to identify and segment grains without requiring manually annotated data. In the workflow we transform the raw pixel data into explainable numerical representation of superlattice orientations for clustering. Benchmarking results demonstrate the workflow's robustness against noisy images and edge cases, with a processing speed of four images per minute on standard computational hardware. This efficiency makes the workflow scalable to large datasets and makes it a valuable tool for integrating data-driven models into decision-making processes for material design and analysis. For example, one can use this workflow to quantify grain size distributions at varying processing conditions like temperature and pressure and using that knowledge adjust processing conditions to achieve desired superlattice orientations and grain sizes.
Materials Science (cond-mat.mtrl-sci), Computer Vision and Pattern Recognition (cs.CV), Image and Video Processing (eess.IV)
Multichannel Dyson equations for even- and odd-order Green's functions: application to double excitations
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
Gabriele Riva, Théodore Fischer, Stefano Paggi, J. Arjan Berger, Pina Romaniello
We extend the concept of the multichannel Dyson equation that we have recently derived to model photoemission spectra by coupling the one- and the three-body Green's functions, to higher-order Green's functions and to other spectroscopies. We show the general structure of the equations and how one can systematically approximate the corresponding multichannel self-energy. As a particular case, we focus on the coupling of the two-body and the four-body Green's functions in the electron-hole channel to describe neutral excitations. This formulation allows for the description of important many-body effects, such biexcitons, in a natural way. We illustrate our approach by applying it to a two-level model system, which, in a one-particle picture, exhibits single and double excitations. Our method can correctly describe both kinds of excitation, unlike standard approaches, and in good agreement with the exact results.
Strongly Correlated Electrons (cond-mat.str-el)
Nonreciprocal ballistic transport in multi-layer Weyl Semimetal films with surface engineering
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
M. H. Zou, H. Geng, R. Ma, W. Chen, L. Sheng, D. Y. Xing
Weyl semimetal (WSM) thin films possess unique electronic properties that differ from bulk materials. In this article, we study the nonreciprocal ballistic transport of the WSM thin films caused by surface modification. We find that the surface states contribute predominantly to the nonreciprocity, while the bulk states provide a negative correction. Our calculation shows a kind of quantum size effect that the nonreciprocal signal decreases as the WSM film becomes thicker, and diverges when the Fermi energy is near the bottom of a sub-band. On the other hand, it is found that the density of states in multi-layer systems possesses some properties roughly independent of thickness. A single-variable theory is developed to explain it
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 4 figures. arXiv admin note: text overlap with arXiv:2312.12837
Interleaved bond and magnetic frustration in triangular lattice \(Ln\)Cd\(_3\)P\(_3\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
S. J. Gomez Alvarado, J. R. Chamorro, A. R. Jackson, G. Pokharel, R. Gomez, B. R. Ortiz, Suchismita Sarker, L. Kautzsch, L. C. Gallington, R. Seshadri, Stephen D. Wilson
We report the presence of frustrated bond order in the form of short-range charge correlations in the triangular lattice antiferromagnetic compounds \(Ln\)Cd\(_3\)P\(_3\) (\(Ln\) = La, Ce, Pr, and Nd). These compounds feature two-dimensional planes of trigonal-planar CdP\(_3\) units that separate tetrahedral CdP\(_4\) layers; collectively, these sandwich edge-sharing triangular lattice planes of \(Ln\)P\(_6\) octahedra. Diffuse X-ray scattering data reveal an underlying bond instability within the unique CdP\(_3\) units that breaks rotational symmetry along one Cd\(-\)P bond direction, with long-range ordering being frustrated via emergent kagome-ice bond correlations. Our results establish \(Ln\)Cd\(_3\)P\(_3\) as a rare class of materials where frustrated magnetism across a tunable rare-earth triangular network is embedded within a dopable semiconductor with a frustrated bond order instability.
Strongly Correlated Electrons (cond-mat.str-el)
11 pages, 5 figures
Skin-inspired in-sensor encoding of strain vector using tunable quantum geometry
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Zenglin Liu, Jingwen Shi, Jin Cao, Zecheng Ma, Zaizheng Yang, Yanwei Cui, Lizheng Wang, Yudi Dai, Moyu Chen, Pengfei Wang, Yongqin Xie, Fanqiang Chen, Youguo Shi, Cong Xiao, Shengyuan A. Yang, Bin Cheng, Shi-Jun Liang, Feng Miao
Human skin provides crucial tactile feedback, allowing us to skillfully perceive various objects by sensing and encoding complex deformations through multiple parameters in each tactile receptor. However, replicating this high-dimensional tactile perception with conventional materials' electronic properties remains a daunting challenge. Here, we present a skin-inspired method to encode strain vectors directly within a sensor. This is achieved by leveraging the strain-tunable quantum properties of electronic bands in the van der Waals topological semimetal Td -WTe2. We observe robust and independent responses from the second-order and third-order nonlinear Hall signals in Td -WTe2 when subjected to variations in both the magnitude and direction of strain. Through rigorous temperature-dependent measurements and scaling law analysis, we establish that these strain responses primarily stem from quantum geometry-related phenomena, including the Berry curvature and Berry-connection polarizability tensor. Furthermore, our study demonstrates that the strain-dependent nonlinear Hall signals can efficiently encode high-dimensional strain information using a single device. This capability enables accurate and comprehensive sensing of complex strain patterns in the embossed character "NJU". Our findings highlight the promising application of topological quantum materials in advancing next-generation, bio-inspired flexible electronics.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Published in Advanced Functional Materials (2024)
Tilted chiral spin textures in confined nanostructures with in-plane magnetic anisotropy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Wenlei Fu, Haiming Dong, Kai Chang
We demonstrate that nanoconfinement effects and in-plane magnetic anisotropy (IMA) can lead to tilted chiral spin textures in magnetic nanostructures, based on the analysis and simulation of theoretical models of micromagnetism. The tilted skyrmions are induced in confined nanoscale magnets with IMA under perpendicular magnetic fields. The chiral magnetic structures depend significantly on the size of the nanostructures. A controlled string of periodic skyrmion states emerges within the central magnetic domain wall, which can be tuned by the steady magnetic fields and the size of the nanostructures. Non-trivial topological states with non-integer topological charges are achieved by tuning the magnetic fields or the sizes of the nanostructures. Importantly, the periodic switching between the trivial and the non-trivial topological configurations is realized using an alternating magnetic field. Our study reveals an important mechanism for controlling novel skyrmion states via nanoconfinement effects and the IMA in magnetic nanostructures, and also provides a new approach for the development of magnetic field-modulated spin nanodevices.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Novel magnetic-field-free switching behavior in vdW-magnet/oxide heterostructure
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Jihoon Keum, Kai-Xuan Zhang, Suik Cheon, Hyuncheol Kim, Jingyuan Cui, Giung Park, Yunyeong Chang, Miyoung Kim, Hyun-Woo Lee, Je-Geun Park
Magnetization switching by charge current without a magnetic field is essential for device applications and information technology. It generally requires a current-induced out-of-plane spin polarization beyond the capability of conventional ferromagnet/heavy-metal systems, where the current-induced spin polarization aligns in-plane orthogonal to the in-plane charge current and out-of-plane spin current. Here, we demonstrate a new approach for magnetic-field-free switching by fabricating a van-der-Waals magnet and oxide Fe3GeTe2/SrTiO3 heterostructure. This new magnetic-field-free switching is possible because the current-driven accumulated spins at the Rashba interface precess around an emergent interface magnetism, eventually producing an ultimate out-of-plane spin polarization. This interpretation is further confirmed by the switching polarity change controlled by the in-plane initialization magnetic fields with clear hysteresis. We successfully combined van-der-Waals magnet and oxide for the first time, especially taking advantage of spin-orbit torque on the SrTiO3 oxide. This allows us to establish a new way of magnetic field-free switching. Our work demonstrates an unusual perpendicular switching application of large spin Hall angle materials and precession of accumulated spins, and in doing so, opens up a new field and opportunities for van-der-Waals magnets and oxide spintronics.
Materials Science (cond-mat.mtrl-sci), Other Condensed Matter (cond-mat.other), Applied Physics (physics.app-ph)
Accepted by Advanced Materials (2025); 47 pages, 4 main figures, 16 supporting figures
High-Throughput Studies of Novel Magnetic Materials in Borides
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Zhen Zhang, Kirill D. Belashchenko, Vladimir Antropov
Borides are a versatile material family with various properties for valuable applications. Conventional magnetism, such as ferromagnetism and antiferromagnetism in borides, have been extensively studied. However, research on unconventional magnetism in borides where quantum effects are dominant is scarce. Here, we implement a high-throughput workflow combining first-principles calculations, materials prediction, and magnetic properties calculations to discover novel magnetism and magnetic materials in borides. Successfully applying the workflow, we report three families of novel magnetic borides, including two families of borides exhibiting quantum magnetism. One is a family of dimerized quantum magnets among YCrB\(_4\)-type borides, which provides a rare platform for studying the spin-gap quantum critical point. The other is a family of altermagnets among FeMo\(_2\)B\(_2\)-type borides, extending the magnetic orderings exhibited by borides beyond conventional ferromagnetism and antiferromagnetism. We also predict a family of magnetic laminate transition metal borides, known as the MAB phases, in the AlFe\(_2\)B\(_2\)-type family, which provide pure-phase or alloying candidates for studying magnetocaloric materials and the associated magnetic transitions. The workflow is expected to be used in further studies of novel magnetism and magnetic materials.
Materials Science (cond-mat.mtrl-sci)
The electronic structure, crystal fields, and magnetic anisotropy in RECo\(_5\) magnets
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Zhen Zhang, Andrey Kutepov, Leonid Pourovskii, Vladimir Antropov
The current progress in the description of the electronic structure and magnetic properties of rare-earth-based magnets is discussed. We show the typical values of critical parameters that define the physics of these materials for RECo\(_5\) (RE = rare earth atom) using several currently popular electronic structure methods. The magnetic moments and magnetic anisotropy of 4 atoms are obtained using several different approaches, including the total energy in constrained DFT and crystal field theory in DFT+HI methods. We also propose a Hund's rule constrained density functional method for the studies of the ground and excited states of magnets containing rare earth atoms. The method is applied to the RECo\(_5\) family of magnets. The applicability and future extensions are discussed. The technique is suitable for high-throughput computational searches of new rare-earth-containing magnetic materials.
Materials Science (cond-mat.mtrl-sci), Strongly Correlated Electrons (cond-mat.str-el)
Defect Phonon Renormalization during Nonradiative Multiphonon Transitions in Semiconductors
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Junjie Zhou, Shanshan Wang, Menglin Huang, Xin-Gao Gong, Shiyou Chen
As a typical nonradiative multiphonon transition in semiconductors, carrier capture at defects is critical to the performance of semiconductor devices. Its transition rate is usually calculated using the equal-mode approximation, which assumes that phonon modes and frequencies remain unchanged before and after the transition. Using the carbon substitutional defect (\(\text{C}_\text{N}\)) in GaN as a benchmark, here we demonstrate that the phonon renormalization can be significant during defect relaxation, which causes errors as large as orders of magnitude in the approximation. To address this issue, we consider (i) Duschinsky matrix connecting the initial-state and final-state phonons, which accounts for the changes in phonon modes and frequencies; and (ii) the off-diagonal contributions in total transition matrix element, which incorporates the cross terms of electron-phonon interactions between different modes. With this improvement, the calculated transition rates show agreements with experimental results within an order of magnitude. We believe the present method makes one step forward for the accurate calculation of multiphonon transition rate, especially in cases with large defect relaxations.
Materials Science (cond-mat.mtrl-sci)
Anisotropy of PbTe nanowires with and without a superconductor
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Zonglin Li, Wenyu Song, Shan Zhang, Yuhao Wang, Zhaoyu Wang, Zehao Yu, Ruidong Li, Zeyu Yan, Jiaye Xu, Yichun Gao, Shuai Yang, Lining Yang, Xiao Feng, Tiantian Wang, Yunyi Zang, Lin Li, Runan Shang, Qi-Kun Xue, Ke He, Hao Zhang
We investigate the anisotropic behaviors in PbTe and PbTe-Pb hybrid nanowires. In previous studies on PbTe, wire-to-wire variations in anisotropy indicate poor device control, posing a serious challenge for applications. Here, we achieve reproducible anisotropy in PbTe nanowires through a substantial reduction of disorder. We then couple PbTe to a superconductor Pb, and observe a pronounced deviation in the anisotropy behavior compared to bare PbTe nanowires. This deviation is gate-tunable and attributed to spin-orbit interaction and orbital effect, controlled by charge transfer between Pb and PbTe. These results provide a guidance for the controlled engineering of exotic quantum states in this hybrid material platform.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Observation of topological Anderson Chern insulator phase in MnBi\(_4\)Te\(_7\) monolayer
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Anqi Wang, Bo Yin, Zikang Su, Shangjie Tian, Guoan Li, Xiaofan Shi, Xiao Deng, Yupeng Li, Zhiyuan Zhang, Xingchen Guo, Qinghua Zhang, Lin Gu, Xingjiang Zhou, Bingbing Tong, Peiling Li, Zhaozheng Lyu, Guangtong Liu, Fanming Qu, Ziwei Dou, Yuan Huang, Hechang Lei, Hongming Weng, Zhong Fang, Quansheng Wu, Li Lu, Jie Shen
The correlation of topology and disorder has attracted great intention due to appropriate disorder could induce the phase transition between trivial and nontrivial topological states. While it is widely recognized that strong disorder can produce rich phase diagrams in topological nontrivial states, moderate disorder has been proposed to induce transitions into topologically nontrivial phases counter-intuitively, leading to the concept of topological Anderson insulators. This phenomenon has been theoretically explored and simulated in various systems, yet experimental realization in solid state systems has remained elusive due to challenges in controlling disorder. Here, we report the experimental observation of Chern insulator state signed by the coexistence of quantized Hall plateau and zero longitudinal resistance in monolayer MnBi\(_4\)Te\(_7\) Hall bar device, which originally hosts a trivial insulating state with Chern number \(C\) = 0 in clean limit. We demonstrate that the observed trivial to nontrivial transition in this monolayer device can be attributed to disorder, evidenced by universal conductance fluctuations. Our findings substantiate the existence of a long-sought topological Anderson Chern insulator in real materials, a unique variant of the topological Anderson insulator characterized by broken time-reversal-symmetry.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
45 pages, 4 main figures, 5 extended data figures, 5 supplementary figures
The unbearable lightness of Restricted Boltzmann Machines: Theoretical Insights and Biological Applications
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-09 20:00 EST
Giovanni di Sarra, Barbara Bravi, Yasser Roudi
Restricted Boltzmann Machines are simple yet powerful neural networks. They can be used for learning structure in data, and are used as a building block of more complex neural architectures. At the same time, their simplicity makes them easy to use, amenable to theoretical analysis, yielding interpretable models in applications. Here, we focus on reviewing the role that the activation functions, describing the input-output relationship of single neurons in RBM, play in the functionality of these models. We discuss recent theoretical results on the benefits and limitations of different activation functions. We also review applications to biological data analysis, namely neural data analysis, where RBM units are mostly taken to have sigmoid activation functions and binary units, to protein data analysis and immunology where non-binary units and non-sigmoid activation functions have recently been shown to yield important insights into the data. Finally, we discuss open problems addressing which can shed light on broader issues in neural network research.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Machine Learning (cs.LG), Data Analysis, Statistics and Probability (physics.data-an)
7 pages, 3 figures. To be published in EPL as di Sarra et al 2025 EPL. Accepted manuscript available online at this https URL
Comparison of bulk properties of wet granular materials using different capillary force approximations
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Meysam Bagheri, Sudeshna Roy, Thorsten Pöschel
We perform Discrete Element Method simulations of wet granular matter in a split-bottom shear cell. To calculate the capillary forces from the liquid bridges between the grains, we used three different approximations. The simulations of the shear cell showed a linear increase in bulk cohesion with the surface tension of the liquid, consistently for all approximations. However, the macroscopic friction coefficient shows only a weak dependence on surface tension.
Soft Condensed Matter (cond-mat.soft)
5 pages, 3 figures, TGF2024
Fate of gapless edge states in two-dimensional topological insulators with Hatsugai-Kohmoto interaction
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
Jan Skolimowski, Wojciech Brzezicki
Topologically protected edge states are the highlight feature of an interface between non-equivalent insulators. The robustness/sensitivity of these states to local single-particle perturbations is well understood, while their stability in the presence of various types of two-particle interactions remains unclear. To add to previous discussions of the Hubbard and unscreened Coulomb interactions, we address this problem from the point of view of infinite-range Hatsugai-Kohmoto interaction. Based on our numerical results for two models of Chern insulators, the Kane-Mele and spinful Haldane model, on a ribbon geometry with zig-zag edges, we argue that any finite interaction strength \(U\) is sufficient to open a charge gap in the spectrum of either Chern insulator. We explain the differences between the two cases and present how their edge states phase out as the system enters the strongly correlated phase. We show that the closing of the many-body gap in periodic variants of these models can be connected to the onset of hybridization between the edge and bulk modes in finite geometries. Providing an example of the bulk-boundary correspondence in systems where there is a topological phase transition without closing of the spectral gap.
Strongly Correlated Electrons (cond-mat.str-el), Other Condensed Matter (cond-mat.other)
14 pages, 5 figures
Kramers doublet and magnetic properties of the double perovskite Ba2NaOsO6
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
Bulk magnetic properties of Ba2NaOsO6 are examined in the context of an appropriate space group and an atomic model of the Kramers doublet for the osmium ion. It possesses symmetry demanded by the Wykoff position assigned to the osmium ion in a canted ferromagnet. Calculated and measured values of the saturation magnetic moment, and x-ray magnetic dichroic signals (XMCD) at osmium L2 and L3 absorption edges agree well.
Strongly Correlated Electrons (cond-mat.str-el)
Hypersonic acoustic wave control via hyperuniform phononic nanostructures
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Michele Diego, Jade Hardouin, Gabrielle Mazevet-Schargrod, Matteo Pirro, Byunggi Kim, Roman Anufriev, Masahiro Nomura
Controlling hypersonic surface acoustic waves is crucial for advanced phononic devices such as high-frequency filters, sensors, and quantum computing components. While periodic phononic crystals enable precise bandgap engineering, their ability to suppress acoustic waves is limited to specific frequency ranges. Here, we experimentally demonstrate the control of surface acoustic waves using a hyperuniform arrangement of gold nanopillars on a lithium niobate layer. The hyperuniform structure exhibits characteristics of both random and ordered systems, leading to an overall reduction in acoustic transmission and the formation of bandgap-like regions where phonon propagation is strongly suppressed. We further demonstrate effective waveguiding by incorporating linear and S-shaped waveguides into the hyperuniform pattern. Both simulations and experiments confirm high transmission through the waveguides at frequencies within the bandgaps, demonstrating the flexibility of hyperuniform structures to support waveguides of complex shapes. These findings provide a novel approach to overcoming the limitations of traditional phononic crystals and advancing acoustic technologies in applications such as mechanical quantum computing and smartphone filters.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
5 pages, 3 figures
Simultaneous MOKE imaging and measurement of magneto-resistance with vector magnet: a low noise customized setup for low field magnetic devices and thin films characterization
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Imtiaz Noor Bhatti, Ilyas Noor Bhatti, L. G. Enger, P. Victor, B. Guillet, M. Lam Chok Sing, O. Rousseau, V. Pierron, S. Lebargy, J. Camarero, L. Mechin, S. Flament
Here we report a custom design setup for the simultaneous measurement of magneto-resistance and MOKE imaging in longitudinal configuration for characterization of magnetic thin-films and sensors. The setup is designed so as to cope with a small signal to noise ratio of initial images and to allow sensitive magnetoresistance (MR) measurement at low field. An improved differential algorithm is used to get a good enough contrast of the magnetic images and get rid of beam illumination or small camera gain fluctuations. Home made power supply and pre-amplifier stage were designed so as to reduce the low frequency noise as well as the thermal electrical noise. A vector magnet is used to produce rotational magnetic field so as to study the magnetic anisotropy and calculate the anisotropic constants in magnetic thin films. Magnetoresistive sensors patterned on epitaxial La\(_{0.67}\)Sr\(_{0.33}\)MnO\(_3\) (LSMO) thin film have been characterized with this setup. The Images of the magnetization reversal process as well as the local magnetization loops deduced from these images provided evidence of a magnetic uniaxial anisotropy induced by the vicinal substrate. The magnetic anistropic constant of the films was then inferred from the MR measurements.
Materials Science (cond-mat.mtrl-sci)
9 Pages, 9 Figures
Anomalous Reversal of Stability in Mo-containing Oxides: A Difficult Case Exhibiting Sensitivity to DFT+U and Distortion
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Tzu-chen Liu, Dale Gaines II, Hyungjun Kim, Adolfo Salgado-Casanova, Steven B. Torrisi, Chris Wolverton
Accurate predictions of the properties of transition metal oxides using density functional theory (DFT) calculations are essential for the computational design of energy materials. In this work, we investigate the anomalous reversal of the stability of structural distortions (where distorted structures go from being energetically favorable to sharply unfavorable relative to undistorted ones) induced by DFT+U on Mo d-orbitals in layered AMoO\(_2\) (A = Li, Na, K) and rutile-like MoO\(_2\). We highlight the significant impact of varying U\(_{\text{eff}}\) values on the structural stability, convex hull, and thermodynamic stability predictions, noting that deviations can reach up to the order of 100 meV/atom across these energetic quantities. We find the transitions in stability are coincident with changes in the electron localization and magnetic behavior. The anomalous reversal persists across PBE, r\(^2\)SCAN functionals, and also with vdW-dispersion energy corrections (PBE+D3). In Mo-containing oxide systems, high U\(_{\text{eff}}\) leads to inaccurate descriptions of physical quantities and structural relaxations under artificial symmetry constraints, as demonstrated by the phonon band structures, the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional results, and comparisons with experimental structural data. We conclude that high U\(_{\text{eff}}\) values (around 4 eV and above, depending on the specific structures and compositions) might be unsuitable for energetic predictions in A-Mo-O chemical spaces. Our results suggest that the common practice of applying DFT+U to convex hull constructions, especially with high U\(_{\text{eff}}\) values derived from fittings, should be carefully evaluated to ensure that ground states are correctly reproduced, with careful consideration of dynamic stability and possible energetically favorable distortions.
Materials Science (cond-mat.mtrl-sci), Computational Physics (physics.comp-ph)
25 pages, 7 figures
Bit reset protocols that obey activity-constrained speed limits do not minimize work for a given speed
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-09 20:00 EST
Daan Mulder, Thomas E. Ouldridge, Pieter Rein ten Wolde
The goal of thermodynamic optimal control theory is to find protocols to change the state of a system from an initial to a desired final distribution, within a finite time, with the least possible expenditure of work. The optimal protocol is closely linked to the intrinsic dynamics of the system at hand. The fact that these dynamics can vary widely has made a general solution elusive. Recent years have seen great progress by recasting the question in terms of a quantity called total activity, i.e. the average number of jumps between states of the system, rather than the time that the operation is allowed to take. This perspective has allowed for general expressions for the minimal work as a function of the total activity, and the minimal total activity required for a given work. The expression for minimal total activity can be recast as an apparent minimal operation time or speed limit. However, it is unclear whether protocols optimized under a constrained activity actually require the lowest work input for a given operation time. In the context of bit reset, we show that directly minimizing work for a given operation time leads to protocols that require significantly less work to perform the operation than the activity-constrained protocol of the same duration. We show how the resulting protocols differ. One reason for the difference is the fact that the activity rate is not constant over the course of the protocol: it depends on both the transition rates and the distribution of the bit, both of which change during the copy operation. In the limit of long protocol duration, we find an expression for the difference between the resulting minimal work for both optimization schemes, for a general class of dynamics. The time-constrained approach always outperforms the activity-constrained approach for a given constrained duration, and the difference in work can be arbitrarily large.
Statistical Mechanics (cond-mat.stat-mech)
15 pages, 3 figures
Partition function zeros for the Blume-Capel model on a complete graph
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-09 20:00 EST
Yulian Honchar, Mariana Krasnytska, Bertrand Berche, Yurij Holovatch, Ralph Kenna
In this paper we study finite-size effects in the Blume-Capel model through the analysis of the zeros of the partition function. We consider a complete graph and make use of the behaviour of the partition function zeros to elucidate the crossover from effective to asymptotic properties. While in the thermodynamic limit the exact solution yields the asymptotic mean-field behaviour, for finite system sizes an effective critical behaviour is observed. We show that even for large systems, the criticality is not asymptotic. We also present insights into how partition function zeros in different complex fields (temperature, magnetic field, crystal field) give different precision and provide us with different parts of the larger picture. This includes the differences between criticality and tricriticality as seen through the lens of Fisher, Lee-Yang, and Crystal Field zeros.
Statistical Mechanics (cond-mat.stat-mech)
Submitted to Low Temperature Physics
A numerical toy model of Langevin dynamics provides real-time visualization of colloidal microdroplet evaporation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Gennadiy Derkachov, Tomasz Jakubczyk, Sima Alikhanzadeh-Arani, Tomasz Wojciechowski, Daniel Jakubczyk
We have developed and tested a simplified but versatile numerical model of nanoparticles' aggregation using Langevin dynamics. The model is particularly capable of simulating aggregation in an evaporating (or condensing) microdroplet. It runs on a graphics processing unit (GPU), which makes it sufficiently fast for real-time conceptualization tasks. We have verified the results of modeling against the findings from two types of experiments we conducted in electrodynamic traps. Firstly, our model helped us to elucidate the phenomenon of scattering `revival', often observed during the evaporation of composite microdroplets. Further on, we were able to mimic our experiments, in which the microdroplets were dried up to form nanoparticle (NP) aggregates, and then soft-landed. Thus we could compare model predictions with SEM imaging. The model was tested for up to \(2.5\times 10^5\) nanoparticles of several coexisting types. Several types of interactions can be accounted for: inter-particle: Lennard-Jones and Coulomb; external: dispersion medium viscosity, centrifugal force, gravity, surface tension, and interface movement. Brownian motion of nanoparticles can be freely controlled. The core program is accompanied by scripts extracting statistical NP aggregates properties in post-processing -- fractal dimension and radial distribution functions. The codes are made available in public repositories. Several diverse evolution scenarios are presented.
Soft Condensed Matter (cond-mat.soft), Atmospheric and Oceanic Physics (physics.ao-ph), Computational Physics (physics.comp-ph)
Susceptible-Infected-Susceptible dynamics with mitigation in connection of infected population
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-09 20:00 EST
K. M. Kim, C. Dias, M. O. Hase
The susceptible-infected-susceptible epidemic model is analyzed through a degree-based mean-field approach. In this work, a mitigation factor is introduced in the probability of finding an infected individual following an edge. This modification simulates situations where the infected population reduces its participation in the dynamics of disease propagation, as may happen with the seclusion or hospitalization of infected individuals. A detailed investigation of this new model and its comparison to the original one (without the mitigation factor) was performed on the Barabási-Albert network, where some important results were analytically accessible.
Statistical Mechanics (cond-mat.stat-mech)
Braz. J. Phys. 53, 94 (2023)
Probability distributions of the order parameter of the \(O(N)\) model
New Submission | Statistical Mechanics (cond-mat.stat-mech) | 2025-01-09 20:00 EST
Adam Rançon, Bertrand Delamotte, Lovro Šaravanja, Ivan Balog
We study the probability distribution function (PDF) of the order parameter of the three-dimensional \(O(N)\) model at criticality using the functional renormalisation group. For this purpose, we generalize the method introduced in [Balog et al., Phys. Rev. Lett. {}, 210602 (2022)] to the \(O(N)\) model. We study the large \(N\) limit, as well as the cases \(N=2\) and \(N=3\) at the level of the Local Potential Approximation (LPA), and compare our results to Monte Carlo simulations. We compute the entire family of universal scaling functions, obtained in the limit where the system size \(L\) and the correlation length of the infinite system \(\xi_\infty\) diverge, with the ratio \(\zeta=L/\xi_\infty\) constant. We also generalize our results to the approach of criticality from the low-temperature phase where another infinite family of universal PDF exists. We find that the LPA describes very well the functional form of the family of PDFs, once we correct for a global amplitude of the (logarithm of the) PDF and of \(\zeta\).
Statistical Mechanics (cond-mat.stat-mech)
20 pages, 11 figures
Interaction-enhanced many-body localization in a 1D quasiperiodic model with long-range hopping
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-09 20:00 EST
We study the many-body localization (MBL) transition in an 1D exactly solvable system with long-range hopping and quasiperiodic on-site potential introduced in Phys. Rev. Lett. 131, 186303 (2023). Unlike other disorder or quasiperiodic model, an interaction-enhanced MBL happens in the moderate interaction regime, which is dubbed as the interaction-enhanced MBL. This counterintuitive phenomenon can be understood by noticing the fragility of the critical band lying at the bottom of the spectrum. The fragile band is localized by other localized states once the interaction is turned on. This mechanism can be verified by introducing a mean-field theory description which can derive highly excited states with high accuracy. The effectiveness of this mean-field theory is captured by the quasihole physics, validated by the particle entanglement spectra.
Disordered Systems and Neural Networks (cond-mat.dis-nn)
8 pages, 8 figures. Comments are welcome
Taxonomy of amorphous ternary phase diagrams: the importance of interaction parameters
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Yasin Ameslon, Hao Liu, Jens Harting, Olivier J.J. Ronsin, Olga Wodo
Phase diagrams offer a comprehensive representation of the thermodynamics of multi-component systems. However, for ternary amorphous systems, the different possible phase diagram types and their existence conditions are still unclear. Based on the systematic screening of the parameter space for three amorphous ternary material systems representative of polymer, small molecule, and solvent materials, we report identifying twenty-one phase diagram types generated using Flory-Huggins theory. The proposed classification relies on the number of immiscible material pairs, distinct miscibility gaps, and three-phase regions. We infer existence rules by mapping the type of phase diagram to the range of interaction parameters in the three-dimensional parameter space. Depending on the number of immiscible pairs (0, 1, 2, or 3), four well-known phase-diagram types are found to be very likely. However, numerous uncommon phase diagrams are observed within a small parameter window around the critical interaction parameter values. Regarding the processability window, the size of the miscible region becomes sensitive to interaction parameter variations, mainly when they are close to critical values. The sensitivity decreases for materials with increasing molar size. Finally, the paper includes a successful comparison of simulated phase diagrams with experimental data, showcasing the real-world relevance of this theoretical analysis and its applicability for optimizing solution processing methods efficiently.
Materials Science (cond-mat.mtrl-sci)
Anomalous topological edge modes in a periodically-driven trimer lattice
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Mohammad Ghuneim, Raditya Weda Bomantara
Periodically driven systems have a longstanding reputation for establishing rich topological phenomena beyond their static counterpart. In this work, we propose and investigate a periodically driven extended Su-Schrieffer-Heeger (SSH) model with three sites per unit cell, obtained by replacing the Pauli matrices with their \(3\times 3\) counterparts. The system is found to support a number of edge modes over a range of parameter windows, some of which have no static counterparts. Among these edge modes, of particular interest are those which are pinned at a specific quasienergy value. Such quasienergy-fixed edge modes arise due to the interplay between topology and chiral symmetry, which are typically not expected in a three-band static model due to the presence of a bulk band at the only chiral-symmetric energy value, i.e., zero. In our time-periodic setting, another chiral-symmetric quasienergy value exists at half the driving frequency, which is not occupied by a bulk band and could then host chiral-symmetry-protected edge modes (\(\pi\) modes). Finally, we verify the robustness of all edge modes against spatial disorder and briefly discuss the prospect of realizing our system in experiments.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Reflections of topological properties in the planar-Hall response for semimetals carrying pseudospin-1 quantum numbers
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
We continue our investigations of the nature of the linear-response tensors in planar-Hall and planar-thermal Hall configurations, involving three-dimensional nodal-point semimetals, by considering here nodes hosting pseudospin-1 quasiparticles. Such systems exemplify multifold semimetals, as they have three bands crossing at a nodal point. We derive the explicit expressions of the electric, thermoelectric, and thermal coefficients, when the nodes are subjected to the combined influence of an electric field (and/or temperature gradient) and a weak (i.e., nonquantizing) magnetic field. In order to have a complete description, we consider the effects of the Berry curvature and the orbital magnetic moment on an equal footing, both of which originate from the underlying topological features of the bandstructure. Going beyond our previous works, we determine the out-of-plane response comprising the intrinsic anomalous-Hall and the Lorentz-force-contributed currents, and chalk out the effects of internode-scatterings as well. Our theoretical explorations shed light on the mechanisms of transport in multifold semetals, which are being investigated in contemporary experiments.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), High Energy Physics - Theory (hep-th)
follow-up paper of arXiv:2405.14844 and arXiv:2408.01422; formulae from arXiv:2411.18434 used
Signatures of higher order skyrmionic textures revealed by magnetic force microscopy
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Sabri Koraltan, Joe Sunny, Tamer Karaman, Reshma Peremadathil-Pradeep, Emily Darwin, Felix Büttner, Dieter Suess, Hans Josef Hug, Manfred Albrecht
Higher-order skyrmions and antiskyrmions are topologically protected spin textures with an integer topological charge other than \(\pm 1\) and nucleate from topological point defects in regular Bloch walls, known as vertical Bloch lines. So far, they have only been observed using Lorentz transmission electron microscopy. In this work, we show that higher-order spin textures coexisting in Co/Ni multilayers at room temperature can be visualized by high-resolution magnetic force microscopy (MFM). The experimental results are supported by micromagnetic simulations confirming that different spin objects give rise to distinct MFM contrast in full agreement to our observations.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
7 pages, 5 figures
Controlled probing of Anderson localization and non-Hermitian skin effect via topolectrical circuits
New Submission | Disordered Systems and Neural Networks (cond-mat.dis-nn) | 2025-01-09 20:00 EST
The Anderson localization (AL) and the non-Hermitian skin effect (NHSE) are two distinct wavefunction-localization phenomena arising out of disorder and non-reciprocity, respectively. An integration of both in a single framework will provide a platform to study the interplay between the two. In this connection, we consider the one-dimensional Aubry-André (AA) model, which has garnered significant attention among the disordered models due to its self-dual properties. Hence, we investigate a non-reciprocal AA model with complex phase modulation and implement it in suitably designed topolectrical circuits featuring an interface, segregating two non-equivalent circuit networks. In the circuit, the voltage profile localizes at the interface due to the NHSE, while the AL limits localization phenomena within the vicinity of the excitation node. This competing phenomenon leads to a controllable, node-dependent localization or even partial delocalization of the output voltage. Our results not only provide a practical platform for experimentally studying and controlling the wave localization phenomenon but also highlight the potential of circuit architectures in designing highly sensitive sensors and information transfer in communication devices.
Disordered Systems and Neural Networks (cond-mat.dis-nn), Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Applied Physics (physics.app-ph), Quantum Physics (quant-ph)
11 pages, (5+2) figures
Catalytic activity of Al-Cu-Fe-Ni-Cr high entropy alloy
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Yogesh Kumar Yadav, Mohammad Abu Shaz, Thakur Prasad Yadav
Magnesium hydride (MgH2) is a promising material for hydrogen storage because of its abundance and beneficial properties, such as high storage capacity and cost-effectiveness under mild conditions. Despite of these benefits, MgH2 unfavorable thermodynamics and kinetics make it difficult to use in real applications. In this work, the hydrogen storage properties of MgH2have been improved using Al-Cu-Fe-Ni-Cr high entropy alloy (HEA) based catalysts, which has been synthesized via mechanical alloying. The experimental findings show that the beginning desorption temperature of MgH2significantly lowered from 425°C to 180°C by adding 5 wt. % Al-Cu-Fe-Ni-Cr HEA in MgH2. Moreover, the catalyst shows enhanced kinetics, attaining 7.3 wt. % hydrogen absorption in 3 minutes at 320°C with 15 atm hydrogen pressure, and ~5 wt. % desorption in 6 minutes at 320°C. These results highlight, how much lower its desorption temperature is than those of other well-known catalysts. Over a span of 25 cycles, MgH2 catalyzed by Al-Cu-Fe-Ni-Cr HEA exhibits remarkable cyclic stability with negligible fluctuations (~ 0.05 wt. %).After a thorough characterization of the materials, a workable catalytic mechanism for HEA was proposed in light of the results.
Materials Science (cond-mat.mtrl-sci)
39 pages, 10 Figures
Incommensurate quantum magnet based on 4f-electron in a zigzag spin-1/2 chain of YbCuS\(_2\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
T. Onimaru, Y. Ohmagari, S. Mizutani, R. Yamamoto, H. Kaneshima, C. Moriyoshi, D. T. Adroja, D. Khyalyavin, P. Manuel, H. Saito, C. Hotta
We performed high-resolution powder neutron diffraction experiments and discovered an elliptic helical incommensurate magnetic structure in the semiconducting rare-earth magnet YbCuS2, featuring effective spin-1/2 Yb\(^{3+}\) ions that form a zigzag chain. Upon cooling the sample to 0.2 K, we observed very weak magnetic peaks indexed with an incommensurate propagation vector k = [0, 0.305, 0] along the zigzag chain. The magnitude of the magnetic moment is at least one-third smaller than the expected value for the Yb\(^{3+}\) Kramers doublet ground state. In an applied magnetic field, up-up-down magnetic order was observed at 7.5 T, characterized by diffraction peaks indexed with k = [0, 1/3, 0] and substantial uniform magnetic components. These observations agree well with theoretical calculations based on the density matrix renormalization group for a zigzag spin-1/2 model with isotropic Heisenberg interactions and off-diagonal symmetric \(\Gamma\)-type exchange interactions derived from material parameters. The theory elucidates the quantum mechanical nature of the incommensurate magnetism as remnant off-diagonal spin correlations in a nematic dimer-singlet state.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
5 pages, 4 figures
Single-Atom Catalysis: An Opportunity For Surface Science
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Over the past decade, extensive research into single-atom catalysts (SACs) has revealed that the catalytic behavior of metal adatoms is highly dependent on how they interact with their support. A strong dependence on the local coordination environment has led to comparisons with metal-organic complexes, and there is growing excitement about the potential to fine-tune SACs by controlling the adsorption geometry. The rise of computational screening to identify the optimal support-metal combinations underscores the need for rigorous benchmarking of theoretical methods, to validate realistic geometries, mechanisms, and the impact of adsorption on stability and catalytic activity. The surface science approach is particularly well-suited for this task because it allows to precisely determine the geometry of the metal atom and interpret its catalytic behavior. Moreover, the effects of temperature and molecular adsorption on the model catalysts stability can be studied in isolation, and conclusions drawn from UHV studies tested in increasingly common near-ambient pressure and electrochemical setups. This perspective highlights recent breakthroughs and specific systems, including metal oxides, metal-organic frameworks, and carbon nitrides, where insights from surface science experiments can significantly advance understanding in this rapidly evolving field.
Materials Science (cond-mat.mtrl-sci)
Surface Science 754 (2025) 122687
Hallmarks of Spin Textures for High-Harmonic Generation
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
Francesco Gabriele, Carmine Ortix, Mario Cuoco, Filomena Forte
Spin-orbit coupling and quantum geometry are fundamental aspects in modern condensed matter physics, with their primary manifestations in momentum space being spin textures and Berry curvature. In this work, we investigate their interplay with high-harmonic generation (HHG) in two-dimensional non-centrosymmetric materials, with an emphasis on even-order harmonics. Our analysis reveals that the emergence of finite even-order harmonics necessarily requires a broken twofold rotational symmetry in the spin texture, as well as a non-trivial Berry curvature in systems with time-reversal invariance. This symmetry breaking can arise across various degrees of freedom and impact both spin textures and optical response via spin-orbit interactions. These findings underscore the potential of HHG as a powerful tool for exploring electronic phases with broken rotational symmetry, as well as the associated phase transitions in two-dimensional materials. This approach provides novel perspectives for designing symmetry-dependent nonlinear optical phenomena.
Strongly Correlated Electrons (cond-mat.str-el)
6 pages, 2 figures
Solvent-triggered shape change in gradient-based 4D printed bilayers: case study on semi-crystalline polymer networks
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Lorenzo Bonetti, Aron Cobianchi, Daniele Natali, Stefano Pandini, Massimo Messori, Maurizio Toselli, Giulia Scalet
We propose an approach to 4D print solvent-triggered, gradient-based bilayers made of semi-crystalline crosslinked polymer networks. Out-of-plane bending is obtained after immersion in the solvent, exploiting the different swelling degrees of the layers resulting from crosslinking gradients. Lastly, a beam model of the shape transformation is applied and experimentally validated.
Soft Condensed Matter (cond-mat.soft), Materials Science (cond-mat.mtrl-sci)
This work was funded by the European Union ERC CoDe4Bio Grant ID 101039467 under the funding programme Horizon Europe
Soft Matter, 2024, 20, 4544-4547
Phenomenological modeling of the stress-free two-way shape-memory effect in semi-crystalline networks: Formulation, numerical simulation, and experimental validation
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Matteo Arricca, Nicoletta Inverardi, Stefano Pandini, Maurizio Toselli, Massimo Messori, Ferdinando Auricchio, Giulia Scalet
Polymers exhibiting the stress-free two-way shape-memory effect (SME) represent an appealing solution to achieve self-standing reversible actuation that is a fundamental feature required by numerous applications. The present paper proposes a one-dimensional continuum phenomenological framework to model single-component semi-crystalline polymer networks exhibiting both the one-way SME and the two-way SME under stress and stress-free conditions. A comprehensive experimental campaign is first performed on semi-crystalline networks based on poly(\(\varepsilon\)-caprolactone) (PCL) to characterize the mechanical and thermal properties as well as the one-way and two-way shape memory behavior of the material under different thermo-mechanical conditions. The results guide the formulation of the model, elucidating the selection of the control and phase variables and motivating the choice of their evolution laws. Model capabilities are then demonstrated against experimental data. All the phenomena that influence the stress-free two-way SME, including the actuation temperature, heating/cooling rates, applied stress/strain, and the amount of skeleton and actuation phase, are analyzed and discussed, giving new important insight for application development.
Soft Condensed Matter (cond-mat.soft)
This work was funded by the European Union ERC CoDe4Bio Grant ID 101039467 under the funding programme Horizon Europe
European Journal of Mechanics - A/Solids, Volume 105, May-June 2024, 105245
The importance of being discrete -- An agent-based model for active nematics and more
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Mathieu Dedenon, Carles Blanch-Mercader, Karsten Kruse, Jens Elgeti
Living systems are composed of discrete units, assembled through a hierarchy of structures, and active, by locally extracting energy from their environment to produce mechanical work. Hydrodynamic theories have been successfully applied to describe the large scale dynamics of active materials. Yet, the hydrodynamic limit requires a separation of scales which is not necessarily fulfilled among living systems. In this work, we propose a novel agent-based model of flexible rods exchanging active force dipoles with nematic symmetry, allowing us to explore their behavior down to the sub-agent scale. We obtain spontaneous flows and self-propulsion of \(+1/2\) topological defects, hallmarks of the hydrodynamic theory of active nematics, even on scales smaller than the individual agent! Moreover, our results go beyond the hydrodynamic framework, identifying novel correlations between orientation and flows or strong asymmetries between contractile and extensile activity. Finally, we show the versatility of our agent-based model by presenting spontaneous flows in three dimensions and nematic tissue growth. Because living systems like cell tissues often exhibit several sources of activity, our framework opens the way for more integrated descriptions of living materials.
Soft Condensed Matter (cond-mat.soft), Biological Physics (physics.bio-ph)
Designing Guidance for Multiple Valley-based Topological States Driven by Magnetic Substrates: Potential Applications at High Temperatures
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Valley-based topological phases offer a wealth of exotic quantum states with tunable functionalities, driven by the valley degree of freedom. In this work, by constructing heterostructures of germanene (silicene, stanene) on various magnetic substrates, we address key tuning factors such as the spin-orbit coupling (SOC) strength of the substrate, magnetic orientations, and stacking orders, all of which govern multiple valley-based topological features. We present a comprehensive guiding principle for the efficient manipulation of these features, achieved simply by designing and modulating the magnetic properties of the underlying substrates. Specifically, increasing the SOC strength of the magnetic substrate acilitates a range of topological phase transitions characterized by different Chern numbers, with many systems exhibiting a transition from quantum valley Hall to quantum anomalous Hall (QAH) states. Additionally, rotating the in-plane magnetic orientation of the substrate enables tunability of the Chern number and chirality, within a moderate range of SOC strength. Furthermore, the antiferromagnetic coupling of the magnetic substrate can induce valley-based QAH states with substantial valley gaps, leveraging its high Curie temperature (TC) to enable the realization of multiple tunable magnetic topologies at elevated temperatures. Our findings provide a straightforward strategy for the design and manipulation of spintronic and valleytronic devices that can potentially operate under high-temperature conditions.
Materials Science (cond-mat.mtrl-sci)
Accelerated Discovery of Vanadium Oxide Compositions: A WGAN-VAE Framework for Materials Design
New Submission | Materials Science (cond-mat.mtrl-sci) | 2025-01-09 20:00 EST
Danial Ebrahimzadeh, Sarah S. Sharif, Yaser M. Banad
The discovery of novel materials with tailored electronic properties is crucial for advancing modern device technologies, yet traditional approaches rely on time-consuming empirical methods. We present an inverse design framework combining enhanced Wasserstein Generative Adversarial Network (WGAN) with specialized Variational Autoencoder (VAE) to accelerate stable vanadium oxide (V-O) discovery for electronic applications. Our framework introduces a WGAN architecture with integrated stability constraints and formation energy predictions, plus a refined VAE utilizing voxel-based representation that captures atomic positions and lattice parameters while maintaining chemical validity. Applying this framework, we generated 451 unique V-O compositions, with 91 structures identified as stable and 44 as metastable under rigorous thermodynamic criteria, including novel V2O3 configurations below the Materials Project convex hull. Electronic structure analysis using spin-polarized DFT+U calculations revealed distinct electronic behaviors, including promising half-metallic characteristics for spintronics and quantum computing applications. Our approach achieves approximately 20% stability rate under strict criteria compared to previous benchmarks, demonstrating its effectiveness for accelerated materials discovery.
Materials Science (cond-mat.mtrl-sci), Disordered Systems and Neural Networks (cond-mat.dis-nn)
11 Figures
Eliminating the confined dark-exciton qubit precession using an externally applied magnetic field
New Submission | Mesoscale and Nanoscale Physics (cond-mat.mes-hall) | 2025-01-09 20:00 EST
Zu-En Su, Dan Cogan, Ido Schwartz, Ayal Beck, David Gershoni
We investigate experimentally and theoretically the behavior of the confined dark exciton in an InAs/GaAs semiconductor quantum dot, under the application of an external magnetic field in Voigt configuration. We show that by varying the magnitude and direction of the external field one can accurately control the dark-exciton fine-structure splitting. In addition, we show that the dark-exciton spin state is approximately polarized along the cubic crystallographic directions [100] or equivalents. By comparing our experimental results with a model for the exchange and Zeeman interactions, we find the conditions for nullifying the fine-structure splitting between the two eigenstates of the dark exciton, thereby stopping its qubit precession.
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Quantum Physics (quant-ph)
6 pages, 4 figures, 1 table
Bundling architecture in elastic filaments with applied twist
New Submission | Soft Condensed Matter (cond-mat.soft) | 2025-01-09 20:00 EST
Amit Dawadi, Animesh Biswas, Julien Chopin, Arshad Kudrolli
We investigate the formation of helical multifilament bundles and the torque required to achieve them as a function of applied twist. Hyperelastic filaments with circular cross sections are mounted parallel in a uniform circle onto end-clamps that can move along the twist axis depending on the applied axial load. With increasing twist, the filaments describe a hyperbolic hyperboloid surface before coming into contact in a circle, and then packing in a tight helical bundle in the center with increasing twist. While the bundle appears ordered for sufficiently small number of filaments, they are disordered for large enough number of filaments and applied twist. We reveal with x-ray tomography, that the packing of the filaments becomes disordered following a radial-instability which leads to a decrease in bundle radius, and migration of filaments relative to each other in the bundle. Nonetheless, the helical angle of the filaments in the bundle are found to be essentially constant, resulting in inclination angles which increase with distance from axis of rotation. We develop energy minimization analysis to capture the observed variations in bundle length and torque as a function of number of filaments considering the neo-Hookean nature of the filaments. We show that the bundle geometry and the applied load can be used to describe the non-linear torque profile measured as a function of twist angle.
Soft Condensed Matter (cond-mat.soft)
Three-dimensional spin liquid state in the frustrated \(\mathbf{S = 1/2}\) Heisenberg garnet NaCa\(_{\mathbf{2}}\)Cu\(_{\mathbf{2}}\)(VO\(_{\mathbf{4}}\))\(_{\mathbf{3}}\)
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
Y. Alexanian, R. Kumar, H. Zeroual, B. Bernu, L. Mangin-Thro, R. S. Stewart, J. M. Wilkinson, P. L. Paulose, F. Bert, P. Mendels, B. Fåk, E. Kermarrec
Three-dimensional quantum spin liquids have remained elusive, hindered by reduced quantum fluctuations from larger lattice connectivity inherent to high-dimensional systems. Here, we investigate the remarkable persistence of dynamical short-range magnetic correlations in the nearly body-centered cubic garnet NaCa\(_2\)Cu\(_2\)(VO\(_4\))\(_3\) down to \(T = 50\) mK, two orders of magnitude below its Curie-Weiss temperature. Using a combination of neutron and muon spectroscopies plus numerical simulations, we demonstrate that a spin-liquid phase emerges from the interplay of strongly frustrated exchange interactions and subtle temperature-dependent Jahn-Teller spin-lattice effects.
Strongly Correlated Electrons (cond-mat.str-el), Materials Science (cond-mat.mtrl-sci)
9 pages, 4 figures. Supplementary Information: 3 pages, 4 figures
Learning by Confusion: The Phase Diagram of the Holstein Model
New Submission | Strongly Correlated Electrons (cond-mat.str-el) | 2025-01-09 20:00 EST
George Issa, Owen Bradley, Ehsan Khatami, Richard Scalettar
We employ the "learning by confusion" technique, an unsupervised machine learning approach for detecting phase transitions, to analyze quantum Monte Carlo simulations of the two-dimensional Holstein model--a fundamental model for electron-phonon interactions on a lattice. Utilizing a convolutional neural network, we conduct a series of binary classification tasks to identify Holstein critical points based on the neural network's learning accuracy. We further evaluate the effectiveness of various training datasets, including snapshots of phonon fields and other measurements resolved in imaginary time, for predicting distinct phase transitions and crossovers. Our results culminate in the construction of the finite-temperature phase diagram of the Holstein model.
Strongly Correlated Electrons (cond-mat.str-el), Disordered Systems and Neural Networks (cond-mat.dis-nn)
11 pages, 7 figures