Disordered Systems and Neural Networks
Novel exact solutions of the Duffing equation: stability analysis and application to real non-linear deformation tests
A.D. Berezner, V.A. Fedorov, N.S. Perov et al. (+1 more)
In this study, novel exact solutions of the Duffing equation with their phase portraits have been proposed and reasoned. It is shown that phase trajectories are initially elliptical and become distorted in the unstable area within the growth of the variable parameter. Instability criteria of identified solutions have been determined together with the
Fourier series transformation up to the first and high harmonics in a sense of the physical interpretation. An explicit form for the differential operator, corresponding to considered functions, has been derived with evaluation of its main functional spectrum. Non-isothermal creep tests of different materials were completely described using the Duffing equation via noted solutions up to the fracture as processes with personal deformation response. We successfully examined a relationship between the thermal and
magnetic properties of the
ferromagnetic amorphous
alloy under its non-linear deformation, using the critical exponents. With a high linear correlation between our model and experiments, behaviour of organic and metallic systems is well predicted at the same thermo-mechanical testing conditions on the mesoscale.
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All authors A.D. Berezner, V.A. Fedorov, N.S. Perov, G.V. Grigoriev
Materials Science
Temperature dependence of the spontaneous magnetization of Ni2MnGa and other ferromagnets. The superellipse equation
A. Perevertov
The temperature dependence of the spontaneous magnetization of Ni2MnGa and other ferromagnets can be described in reduced coordinates by the superellipse equation using a single dimensionless parameter. This critical exponent parameter equals 2.4 for Ni2MnGa, 2.7 for nickel and cobalt, 3 for iron and 2.05 for gadolinium. Because reduced magnetization and reduced temperature enter the equation symmetrically, the MS(T) dependence can be measured only in the low-temperature range, from 0 to 0.5TC. The magnetization curve from 0.5TC to TC can then be obtained by interchanging reduced magnetization and temperature in the superellipse equation. In this way, the experimentally challenging task of measuring spontaneous magnetization near TC is avoided, as the behavior near TC is effectively determined from measurements performed near T = 0. The MS(T) dependence in a whole temperature range is fully determined by two parameters - the Curie temperature, TC and the critical exponent, n .
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Soft Condensed Matter
Mobility-induced phase separation in a binary mixture of active Brownian particles
D. Jiménez-Flores, A. Rodríguez-Rivas and J. M. Romero-Enrique
In this paper, we report a Brownian dynamics simulation of the mobility-induced phase separation which occurs in a two-dimensional binary mixture of active soft Brownian particles, whose interactions are modeled by non-additive Weeks-Chandler-Andersen potentials inspired in Lennard-Jones potentials used for glass-forming passive mixtures. The analysis of structural properties, such as the radial distribution functions and the hexatic order parameter, shows that the high-density coexisting state in the binary case is spatially disordered, unlike the solid-like state observed for the monocomponent system. Characterization of the mean-square displacement of the active particles shows that both the low- and high-density coexisting states have diffusive behavior for long times. Thus, the high-density coexisting states are
liquid-like in the binary cases. Moreover, diffusive behavior is also observed in the high-density solid-like state for the monocomponent system, which is driven by the presence of active topological defects.
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Strongly Correlated Electrons
Intriguing Magnetocaloric Effect in Multiferroic Ba3RRu2O9 (R=Ho, Gd, Tb, Nd) with Strong 4d-4f Correlations
Mohit Kumar, Sayan Ghosh, Gourab Roy et al. (+6 more)
Here we demonstrate the magnetocaloric effect (MCE) of a 4d-4f correlated system, namely Ba3RRu2O9 (R= Ho, Gd, Tb, Nd). The compound Ba3HoRu2O9 antiferromagnetically orders at 50 K where both the Ho and Ru-moments order, followed by another phase transition ~ 10 K. Whereas, the compound Ba3GdRu2O9 and Ba3TbRu2O9 orders at 14.5 and 10.5 K respectively, where the ordering of both R and Ru moments are speculated. Our results reveal robust MCE around low-T
magnetic phase transition for all the heavy rare-earth members (Ho, Gd, Tb) in this family. The heavy rare-earth members exhibit an intriguing MCE behavior switching from conventional to non-conventional MCE. Interestingly, the light R-member, Ba3NdRu2O9, orders ferromagnetically below 24 K where Nd-moments order, followed by Ru-ordering below 18 K, exhibits a positive MCE below and above FM-ordering. The compelling MCE are attributed to temperature dependent complex
spin-reorientations for different R-members and anisotropy.
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All authors Mohit Kumar, Sayan Ghosh, Gourab Roy, Ekta Kushwaha, Vincent Caignaert, Wilfrid Prellier, Subham Majumdar, Vincent Hardy, Tathamay Basu
Materials Science
Essential Principles and Practices in X-ray Photoelectron Spectroscopy
Jan Čechal
X-ray photoelectron spectroscopy (XPS) is a widely used technique for chemical analysis of solid surfaces, sensitive to the chemical environments of atoms via core-level binding energy shifts. While modern instruments allow experimental data to be acquired with ease, their evaluation and interpretation remain challenging for newcomers to the field, as a profound knowledge of the method is required for correct analysis. Here we present a concise yet comprehensive overview of the fundamental principles and methodologies of XPS, covering photoemission processes, chemical shifts, charge referencing, peak fitting, and quantification strategies. This overview aims to bridge the gap between data collection and reliable analysis, providing essential knowledge for correct interpretation. By clarifying key concepts and common practices, this work supports improved accuracy in surface chemical characterization using XPS.
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Mesoscale and Nanoscale Physics
A Quantum Framework for Negative Magnetoresistance in Multi-Weyl Semimetals
Arka Ghosh, Sushmita Saha and Alestin Mawrie
We develop a fully
quantum-mechanical theory of negative magnetoresistance in multi-Weyl semimetals in the ${\bf E}\parallel{\bf B}$ configuration, where the
chiral anomaly is activated. The magnetotransport response is governed by Landau quantization and the emergence of multiple
chiral Landau levels associated with higher-order Weyl nodes. These anomaly-active modes have unidirectional dispersion fixed by the node's monopole charge and dominate charge transport. As the
magnetic field increases, individual
chiral branches successively cross the
Fermi energy, producing discrete slope changes in the longitudinal conductivity and a step-like negative magnetoresistance. This quantized
evolution provides a direct experimental signature of multi-Weyl
topology. Bulk Landau levels contribute only at very low fields due to strong disorder scattering and do not affect the anomaly-driven regime. Our results establish a unified, fully
quantum-mechanical framework in which negative magnetoresistance arises from the discrete Landau-quantized spectrum and microscopic
impurity scattering, beyond semiclassical anomaly descriptions.
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Mesoscale and Nanoscale Physics
Supercurrent from the imaginary part of the Andreev levels in non-Hermitian Josephson junctions
Roberto Capecelatro, Marco Marciani, Gabriele Campagnano et al. (+2 more)
We investigate the electronic transport properties of a
superconductor-
quantum dot-
superconductor Josephson junction coupled to a
ferromagnetic metal reservoir in the presence of an external
magnetic field. The device is described by an effective non-Hermitian
Hamiltonian, whose complex
eigenvalues encode the energy (real part) and the broadening (imaginary part) of the Andreev quasi-bound states. When extending the Andreev current formula to the non-Hermitian case, a novel contribution arises that is proportional to the phase derivative of the levels broadening. This term becomes particularly relevant in the presence of exceptional points (EPs) in the spectrum, but its experimental detection is not straightforward. We identify optimal Andreev spectrum configurations where this novel current contribution can be clearly highlighted, and we outline an experimental protocol for its detection. We point out that the phase dependence in the levels imaginary part originates from the breaking of a time-reversal-like
symmetry. In particular, spectral configurations in the broken phase of the
symmetry and without EPs can be obtained, where this novel contribution can be easily resolved. The proposed protocol would allow to probe for the first time a fingerprint of non-Hermiticity in open junctions that is not strictly related to the presence of EPs.
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All authors Roberto Capecelatro, Marco Marciani, Gabriele Campagnano, Roberta Citro, Procolo Lucignano
Disordered Systems and Neural Networks
The disordered Su-Schrieffer-Heeger model
Michael Hilke
Quantum topology categorizes physical systems in integer invariants, which are robust to some deformations and certain types of disorder. A
prime example is the Su-Schrieffer-Heeger (SSH) model, which has two distinct topological phases, the trivial phase with no edge states and the non-trivial phase with zero-energy edge states. The energy dispersion of the SSH model is dominated by a gap around zero energy, which suppresses the transmission. This exponential suppression of the transmission with system length is determined by the Lyapounov exponent. Here we find an analytical expression of the Lyapounov as a function of energy in the presence of both diagonal and off-diagonal disorder. We obtain this result by finding a recurrence relation for the local density, which can be averaged over different disorder configurations. There is excellent agreement between our analytical expression and the numerical results over a wide range of disorder strengths and disorder types. The real space winding number is evaluated as a function of off-diagonal and on-site disorder for possible applications of
quantum topology.
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Statistical Mechanics
Phase transitions in time complexity of Brownian circuits
Kota Okajima and Koji Hukushima
Brownian
circuits perform computations using
stochastic transitions driven by thermal fluctuations. While the energetic costs of such fluctuation-driven computation have been extensively studied within
stochastic thermodynamics, much less is known about its computational complexity, in particular, how computation time scales with
circuit size. In this work, the computation time for explicitly designed Brownian
circuits is numerically investigated via the first-passage time to a completed state. For arithmetic
circuits such as adders, varying the forward transition rate induces a sharp change in the scaling behavior of the mean computation time with
circuit size, from linear to exponential. This change can be interpreted as an easy-hard transition in computational time complexity. The transition suggests that, for meaningful computational tasks, achieving efficient
polynomial-time computation generally requires a finite forward bias corresponding to a nonzero energy input. As a counterexample, we show that arbitrary logical operations can be reduced to an effective one-dimensional
stochastic process in which the zero-bias limit lies within the computationally efficient (easy) regime. However, achieving such a one-dimensional normal form unavoidably leads to an exponential increase in
circuit size. These results reveal a fundamental trade-off between computation time,
circuit size, and energy input in Brownian
circuits and demonstrate that phase transitions in time complexity provide a natural framework for characterizing the cost of fluctuation-driven computation.
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Strongly Correlated Electrons
Fragile Topological Phases and Topological Order of 2D Crystalline Chern Insulators
Hisham Sati and Urs Schreiber
We apply methods of equivariant homotopy theory, which may not previously have found due
attention in condensed matter physics, to classify first the fragile/unstable topological phases of 2D crystalline Chern
insulator materials, and second the possible topological order of their fractional cousins. We highlight that the phases are given by the equivariant 2-Cohomotopy of the Brillouin
torus of
crystal momenta (with respect to wallpaper point group actions) – which, despite the
attention devoted to crystalline Chern
insulators, seems not to have been considered before. Arguing then that any topological order must be reflected in the adiabatic monodromy of gapped
quantum ground states over the covariantized space of these band
topologies, we compute the latter in examples where this group is non-abelian, showing that any potential FQAH anyons must be localized in momentum space. We close with an outlook on the relevance for the search for topological
quantum computing hardware. Mathematical details are spelled out in a supplement.
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Mesoscale and Nanoscale Physics
Modulation of quantum geometry and its coupling to pseudo-electric field by dynamic strain
Surat Layek, Mahesh A. Hingankar, Ayshi Mukherjee et al. (+11 more)
Two-dimensional materials are a fertile ground for exploring
quantum geometric phenomena, with Berry
curvature and its first moment, the Berry
curvature dipole, playing a central role in their electronic response. These
geometric properties influence electronic transport and result in the anomalous and nonlinear
Hall effects, and are typically controlled using static electric fields or strain. However, the possibility of modulating
quantum geometric quantities in real-time remains unexplored. Here, we demonstrate the dynamic modulation of Berry
curvature and its moments, as well as the generation of a pseudo-electric field using time-dependent strain. By placing
heterostructures on a membrane, we introduce oscillatory strain together with an in-plane AC electric field and measure
Hall signals that are modulated at linear combinations of the frequencies of strain and electric field. Our measurements reveal modulation of Berry
curvature and its first moment. Notably, we provide direct experimental evidence of pseudo-electric field that results in an unusual dynamic strain-induced
Hall response. This approach opens up a new pathway for controlling
quantum geometry on demand, moving beyond conventional static perturbations. The pseudo-electric field provides a framework for external electric field-free anomalous
Hall response and opens new avenues for probing the topological properties.
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All authors Surat Layek, Mahesh A. Hingankar, Ayshi Mukherjee, Atasi Chakraborty, Digambar A. Jangade, Anil Kumar, L. D. Varma Sangani, Amit Basu, R Bhuvaneswari, Kenji Watanabe, Takashi Taniguchi, Amit Agarwal, Umesh V. Waghmare, Mandar M. Deshmukh
Superconductivity
Observing unconventional superconductivity via kinetic inductance in Weyl semimetal MoTe$_2$
Mary Kreidel, Julian Ingham, Xuanjing Chu et al. (+10 more)
Identifying the pairing
symmetry of unconventional
superconductors plays an essential role in the ongoing quest to understand correlated electronic matter. A long-standing approach is to study the temperature dependence of the London penetration depth $\lambda$ for evidence of nodal points where the superconducting gap vanishes. However, experimental reports can be ambiguous due to the requisite low-temperature resolution, and the similarity in signatures of nodal quasiparticles and
impurity states. Here we study the pairing
symmetry of Weyl semimetal $T_d$-MoTe$_2$, where previous measurements of $\lambda$ have yielded conflicting results. We utilize a novel technique based on a microwave resontor to measure the kinetic inductance of MoTe$_2$, which is directly related to $\lambda$. The high precision of this technique allows us to observe power-law temperature dependence of $\lambda$, and to measure the anomalous nonlinear Meissner effect – the current dependence of $\lambda$ arising from nodal quasiparticles. Together, these measurements provide smoking gun signatures of nodal superconductivity.
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All authors Mary Kreidel, Julian Ingham, Xuanjing Chu, Jesse Balgley, Ted S. Chung, Abhinandan Antony, Nishchhal Verma, Luke N. Holtzman, Katayun Barmak, Raquel Queiroz, James Hone, Robert M. Westervelt, Kin Chung Fong
Strongly Correlated Electrons
Disentangle Intertwined Interactions in Correlated Charge Density Wave with Magnetic Impurities
J. W. Park, H. Kim and H. W. Yeom
Magnetic impurities in strongly correlated electronic systems serve as sensitive probes to a wide range of many-body
quantum phenomena. Broken
symmetries in such a system can lead to inequivalent
lattice sites, and
magnetic impurities may interact selectively with particular orbitals or sublattices. However, the microscopic mechanisms behind such site-specific interactions have been poorly understood. Here, we explore the behavior of individual Fe adatoms on a cluster-Mott charge-density-wave (CDW) system of 1T-TaS2 utilizing scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Our measurements uncover pronounced site-dependent electronic states of CDW clusters with Fe adatoms, indicating distinct local coupling to cluster-Mott states. DFT calculations identify three distinct types of interactions; hybridization with localized correlated electrons, distorting the CDW cluster, and charge transfer. In particular, the hybridization of Fe 3d and half-filled Ta 5dz2 orbitals suppresses the Mott insulating state for an adatom at the center of a CDW cluster. While the results underscore a crucial role of the direct orbital hybridization and the limitation of the prevailing single-site Kondo
impurity model, they suggest the possibility of controlling entangled interactions separately in a cluster Mott
insulator.
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Statistical Mechanics
Quantum Computing Inspired Approach for Self-Avoiding Walk (SAWs): 2D lattice and 3D lattice SAWs for single chain enumeration
Hemant Mishra, Shubham Singh, Rajeev Singh et al. (+1 more)
We investigate the application of
quantum computing
algorithms to enhance the efficiency of enumerating self-avoiding walks (SAWs), utilizing
quantum properties such as superposition and interference. A
Quantum Amplitude Estimation (QAE)-based
algorithm is developed to enumerate SAWs on both 2D and 3D
lattices. In case of 2D square
lattice, SAWs up to N=71 steps are successfully enumerated within 26.9 minutes - significantly improving upon the classical
algorithm, which required approximately 231 hours(Jensen et al., 2012, J. Phys. A: Math. Theor. 45, 115202). The
algorithm is further extended to 3D cubic
lattices, where SAWs up to N=40 steps are enumerated in 13.06 minutes, compared to the classical result of N=36 in 250 hours (Schram et al., 2011, J. Stat. Mech. P06019). These results demonstrate a substantial reduction in computational time, highlighting the potential of
quantum computing for combinatorial enumeration problems.
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All authors Hemant Mishra, Shubham Singh, Rajeev Singh, Amit Raj Singh
Materials Science
Vapor-solid-solid growth of single-walled carbon nanotubes
Daniel Hedman
Single-walled carbon nanotubes (SWCNTs) are promising for nanoscale electronics and photonics, but practical deployment requires chirality control. Most catalytic chemical vapor deposition (CCVD) growth of SWCNTs proceeds on
liquid metal nanoparticles via a vapor-
liquid-solid (VLS) mechanism and yields broad chirality distributions, whereas improved selectivity has been reported for high-melting-point crystalline catalysts, suggesting vapor-solid-solid (VSS) growth. However, the atomistic mechanism and kinetic of VSS SWCNT growth remain unclear. Here it is shown, using machine-learning interatomic potential-driven molecular dynamics on rhenium nanoparticles, that VSS growth is
diffusion-limited and governed by facet-dependent surface carbon transport coupled to carbon-driven facet reconfiguration without catalyst melting. Surface
diffusion is up to $\sim 50\times$ slower than carbon
diffusion in
liquid iron, imposing a strict upper bound on sustainable carbon supply and producing a narrow growth window: insufficient transport drives carbon accumulation and multiple nucleation, whereas higher temperatures favor graphitic encapsulation. In contrast to defect-free VLS growth, defects persist, indicating slow defect healing, and
equilibrium simulations reveal suppressed edge configurational
entropy with stabilization of zigzag-rich, Klein-decorated edges. Together, these results establish facet
evolution and surface
diffusion as joint regulators of
diffusion-limited VSS growth and motivate stringent control of temperature and carbon supply.
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Other Condensed Matter
Dynamical Phase Transitions in Periodically Driving 1D Ising Model
Yuanyuan Cheng, Yuxia Zhang, Tianhui Qiu et al. (+2 more)
This work investigates dynamical
quantum phase transitions (DQPTs) in a one-dimensional Ising model subjected to a periodically modulated transverse field. In contrast to sudden quenches, we demonstrate that a DQPT can be induced in two distinct ways. First, when the system remains within a given phase–
ferromagnetic (FM) or paramagnetic (PM), a resonant periodic drive can trigger a DQPTs when its frequency matches the energy-level transition of the system. This DQPT is intimately connected to the emergence of Floquet topological phases. The timescale for the transition is governed by the perturbation strength $\lambda'$, the critical mode $k_c$, and its energy gap $\Delta_{k_c}$, following the scaling relation $\tau\propto\Delta_{k_c}\lambda'^{-1}\csc k_c$. Second, for drives across the critical point between the FM and PM phases, low frequencies can always induce DQPT, regardless of resonance. This behavior stems from the degeneracy of the energy-level at the critical point, which ensures that any drive with a frequency lower than the system's intrinsic transition frequency will inevitably excite the system. However, in the high-frequency regime, such excitation will be strongly suppressed, thereby inhibiting the occurrence of DQPTs. This study provides deeper insight into the nonequilibrium dynamics of
quantum spin chains.
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All authors Yuanyuan Cheng, Yuxia Zhang, Tianhui Qiu, Peipei Xin, Bao-Ming Xu
Strongly Correlated Electrons · Cross-listed from quant-ph
Hidden rotation symmetry of the Jordan-Wigner transformation and its application to measurement in quantum computation
Grant Davis and James K. Freericks
Using a global rotation by theta about the z-axis in the
spin sector of the Jordan-Wigner transformation rotates Pauli
matrices X and Y in the x-y-plane, while it adds a global complex phase to fermionic
quantum states that have a fixed number of particles. With the right choice of angles, this relates expectation values of Pauli strings containing products of X and Y to different products, which can be employed to reduce the number of measurements needed when simulating fermionic systems on a
quantum computer. Here, we derive this
symmetry and show how it can be applied to systems in Physics and Chemistry that involve
Hamiltonians with only single-particle (hopping) and two-particle (interaction) terms. We also discuss the consequences of this for finding efficient measurement
circuits in variational ground state preparation.
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Mesoscale and Nanoscale Physics
Open quantum theory of magnetoresistance in mesoscopic magnetic materials
Xian-Peng Zhang, Xiangrong Wang and Yugui Yao
Magnetoresistance (MR) in
magnetic materials arises from
spin-exchange coupling between local moments and itinerant electrons, representing a challenging many-body open-
quantum problem. Here we develop a comprehensive microscopic theory of MR within an open-
quantum-system framework by solving the Liouville-von Neumann equation for a hybrid system of free electrons and local moments using the time-convolutionless projection operator method. Our approach reveals both
ferromagnetic and
antiferromagnetic MR as consequences of temperature- and field-dependent
spin decoherence, encompassing
spin relaxation and dephasing. In particular, the resistance associated with
spin decoherence is governed by the order parameters of
magnetic materials, such as the magnetization in ferromagnets and the Néel vector in antiferromagnets. This theory deepens the fundamental understanding of MR and offers guidance for interpreting and designing experiments on
magnetic materials.
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Superconductivity
Origins of spontaneous magnetic fields in Sr$_2$RuO$_4$
Yongwei Li, Rustem Khasanov, Stephen P. Cottrell et al. (+5 more)
The nature of the broken time reversal
symmetry (BTRS) state in Sr$_2$RuO$_4$ remains elusive, and its relation to superconductivity remains controversial. There are various universal predictions for the BTRS state when it is associated with a multicomponent superconducting order parameter. In particular, in the BTRS superconducting state, spontaneous fields appear around crystalline defects,
impurities, superconducting domain walls and sample surfaces. However, this phenomenon has not yet been experimentally demonstrated for any BTRS
superconductor. Here, we aimed to verify these predictions for Sr$_2$RuO$_4$ by performing
muon spin relaxation ($\mu$SR) measurements on Sr$_{2-y}$La$_{y}$RuO$_4$ single
crystals at ambient pressure and stoichiometric Sr$_2$RuO$_4$ under hydrostatic pressure. The study allowed us to conclude that spontaneous fields in the BTRS superconducting state of Sr$_2$RuO$_4$ appear around non-
magnetic inhomogeneities and, at the same time, decrease with the suppression of $T_{\rm c}$. The observed behaviour is consistent with the prediction for multicomponent BTRS superconductivity in Sr$_2$RuO$_4$. The results of the work are relevant to understanding BTRS superconductivity in general, as they demonstrate, for the first time, the relationship among the superconducting order parameter, the BTRS transition, and
crystal-structure inhomogeneities.
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All authors Yongwei Li, Rustem Khasanov, Stephen P. Cottrell, Naoki Kikugawa, Yoshiteru Maeno, Binru Zhao, Jie Ma, Vadim Grinenko
Materials Science
Matter with apparent and hidden spin physics
Jia-Xin Xiong, Xiuwen Zhang, Lin-Ding Yuan et al. (+1 more)
Materials with interesting physical properties are often designed based on our understanding of the target physical effects. The physical properties can be either explicitly observed ("apparent") or concealed by the perceived
symmetry ("hidden") but still exist. Both are enabled by specific
symmetries and induced by certain physical interactions. Using the underlying approach of condensed matter theory of real materials (rather than schematic model
Hamiltonians), we discuss apparent and hidden physics in real materials focusing on the properties of
spin splitting and
spin polarization. Depending on the enabling
symmetries and underlying physical interactions, we classify
spin effects into four categories with each having two subtypes; representative materials are pointed out. We then discuss the electric tunability and switch of apparent and hidden
spin splitting and polarization in antiferromagnets. Finally, we extend "hidden effects" to views that are farsighted in the sense of resolving the correct atomistic and reciprocal
symmetry and replaced by the incorrect higher
symmetry. This framework could guide and enable systematic discovery of such intriguing effects.
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All authors Jia-Xin Xiong, Xiuwen Zhang, Lin-Ding Yuan, Alex Zunger
Soft Condensed Matter
Dynamics of Interfacial Diffusion Control in Amphiphilic Lipid-Coated Micro-Particles for Stochastic Release Systems
Joonggwon Kim and Dogyun Byeon
The release of hydrophilic solutes from micron scale particulate formulations can be understood as an interfacial transport problem in which
diffusion across a heterogeneous amphiphilic coating competes with dissolution and convective removal in the surrounding medium. Here we reinterpret a glycerin fatty acid ester (GFAE) coated thiamine (vitamin B1) micro particle formulation as a condensed matter system: a soft matter core shell geometry whose effective permeability is set by the nanoscale organization of amphiphilic lipids at the interface. Using in vivo time course serum measurements in mice as a proxy for a
stochastic sink, we compare the coated formulation (UTEV) with a composition matched uncoated comparator (UMFG). Early time systemic appearance is similar, whereas late time levels are enhanced for the coated particles, implying a reduced effective interfacial diffusivity and a broadened release-time distribution. We discuss the results in terms of
diffusion barrier physics, heterogeneous interfacial energetics, and coarse grained transport models that map microstructural coating parameters to macroscopic persistence (AUC).
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Probabilistic Computers for Neural Quantum States
Shuvro Chowdhury, Jasper Pieterse, Navid Anjum Aadit et al. (+3 more)
Neural
quantum states efficiently represent many-body wavefunctions with neural networks, but the cost of Monte Carlo sampling limits their scaling to large system sizes. Here we address this challenge by combining sparse Boltzmann machine architectures with probabilistic computing hardware. We implement a probabilistic computer on field-programmable gate arrays (FPGAs) and use it as a fast sampler for energy-based neural
quantum states. For the two-dimensional transverse-field Ising model at criticality, we obtain accurate ground-state energies for
lattices up to 80$\times$80 (6400
spins) using a custom multi-FPGA cluster. Furthermore, we introduce a dual-sampling
algorithm to train deep Boltzmann machines, replacing intractable marginalization with conditional sampling over auxiliary layers. This enables the training of sparse deep models and improves parameter efficiency relative to shallow networks. We further implement this
algorithm on a single FPGA, demonstrating the training of deep Boltzmann machines for systems as large as $30 \times 30$ (900
spins). Together, these results demonstrate that probabilistic hardware can overcome the sampling bottleneck in variational simulation of
quantum many-body systems, opening a path to larger system sizes and deeper variational architectures.
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All authors Shuvro Chowdhury, Jasper Pieterse, Navid Anjum Aadit, Shaila Niazi, Johan H. Mentink, Kerem Y. Camsari
Quantum Gases
Higgs and Nambu-Goldstone modes in a spin-1 $XY$ model with long-range interactions
Daiki Kawasaki and Ippei Danshita
We theoretically study the collective excitations in a
spin-1 $XY$ model with a quadratic Zeeman term and a long-range interaction that decays algebraically with the distance. Using the
quantum-field theory based on the finite-temperature Green's function formalism, we analyze properties of the Nambu-Goldstone (NG) and
Higgs modes in order to analytically evaluate the damping rate of the
Higgs mode in the $XY$
ferromagnetic ordered phase near the
quantum phase transition to the disordered phase. When the power of the algebraic decay is 3 as in the case of dipole-dipole interactions in Rydberg-atom systems, we show that at two dimensions the excitation energy of the
Higgs mode exhibits a linear dispersion whereas the dispersion of the NG mode becomes proportional to the square root of the momentum. We find that the damping of the
Higgs mode is significantly suppressed by the long-range interaction. We also propose how to excite and probe the
Higgs mode in Rydberg-atom experiments.
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Materials Science
From Berry curvature to quantum metric: a new era of quantum geometry metrology for Bloch electrons in solids
Bohm-Jung Yang
For decades, “geometry" in band theory has largely meant Berry phase and Berry
curvature-quantities that reshape semiclassical dynamics and underpin modern topological matter. Yet the full
geometric content of a Bloch band is richer and encoded in the
quantum geometric tensor (QGT), whose imaginary part is the Berry
curvature and whose real part is the
quantum metric. Here, we briefly review the recent progress in direct experimental access to the QGT in real crystalline solids using the polarization- and
spin-resolved angle-resolved photoemission spectroscopy (ARPES). The extraction of the QGT in momentum space was successfully addressed by two different approaches: One is by introducing quasi-QGT that faithfully represents the QGT and is directly measurable by ARPES. The other is through pseudospin
tomography in a material with simple low energy band structure, which successfully retrieved all
matrix components of the
quantum metric. We discuss the physical meaning of these two recent progresses, their implication/limitation, and open directions.
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Materials Science · Cross-listed from physics.chem-ph
Imaging nanoscale photocarrier traps in solar water-splitting catalysts
Levi D. Palmer, Wonseok Lee, Pushp Raj Prasad et al. (+12 more)
Defects trap photocarriers and hinder
solar water splitting. The nanoscale photocarrier transport, trapping, and recombination mechanisms are usually inferred from ensemble-averaged measurements and remain elusive. Because an individual high-performing nanoparticle photocatalyst may outperform the ensemble average, design rules that would otherwise enhance catalytic efficiency remain unclear. Here, we introduce photomodulated electron energy-loss spectroscopy (EELS) in an optically coupled scanning transmission electron microscope (STEM) to map photocarrier localization. Using rhodium-doped strontium titanate (SrTiO3:Rh)
solar water-splitting nanoparticles, we directly image the carrier densities concentrated at oxygen-vacancy surface trap states. This is achieved by separating photothermal heating from photocarrier populations through experimental and computational analyses of low-loss spectra. Photomodulated STEM-EELS enables angstrom-scale imaging of defect-induced photocarrier traps and their impact on photocatalytic efficiency.
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All authors Levi D. Palmer, Wonseok Lee, Pushp Raj Prasad, Bradley W. Layne, Han-Hsuan Wu, Zejie Chen, Jianguo Wen, Yuzi Liu, Xiaoqing Pan, A. Alec Talin, Akihiko Kudo, Shane Ardo, Joseph P. Patterson, Thomas E. Gage, Scott K. Cushing
Statistical Mechanics
Higher-order response theory in optimal stochastic thermodynamics
Samuel. H. DAmbrosia, Adrianne Zhong and Michael R. DeWeese
Linear response theory has found many applications in statistical physics. One of these is to compute minimal-work protocols that drive nonequilibrium systems between different thermodynamic states, which are useful for designing engineered nanoscale systems and understanding biomolecular machines. We clarify the relationships between linear-response-based approximations used to study optimal protocols in different driving regimes by demonstrating how they arise from a truncation of a causal response, or Volterra, series expansion. We then construct higher-order response terms and discuss the utility and drawbacks of their inclusion in the determination of work-minimizing protocols. We focus on the cases of an overdamped particle in a harmonic trap, and a double well system modeled as a two-state discrete system, ultimately showing that while the inclusion of higher-order response in work approximations can improve predictions of excess work and modestly improve the resulting higher-order optimal protocols, a significant computational expense is incurred while introducing the possibility of predicting arbitrarily low and unphysical negative excess work.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
TLS-induced thermal nonlinearity in a micro-mechanical resonator
Cyril Metzger, Alec L. Emser, Brendon C. Rose et al. (+1 more)
We present experimental evidence of a thermally-driven amplitude-frequency nonlinearity in a thin-film quartz phononic
crystal resonator at millikelvin temperatures. The nonlinear response arises from the coupling of the mechanical mode to an ensemble of microscopic two-level system defects driven out of
equilibrium by a microwave drive. In contrast to the conventional Duffing oscillator, the observed nonlinearity exhibits a mixed reactive-dissipative character. Notably, the reactive effect can manifest as either a softening or hardening of the mechanical resonance, depending on the ratio of thermal to
phonon energy. By combining the standard TLS theory with a thermal conductance model, the measured power-dependent response is quantitatively reproduced and readout-enhanced relaxation damping from off-resonant TLSs is identified as the primary mechanism limiting mechanical coherence. Within this framework, we delineate the conditions under which similar systems will realize this nonlinearity.
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All authors Cyril Metzger, Alec L. Emser, Brendon C. Rose, Konrad W. Lehnert
Strongly Correlated Electrons
Detection of a Rényi Index Dependent Transition in Entanglement Entropy Scaling
Hatem Barghathi and Adrian Del Maestro
The scaling of
entanglement with subsystem size encodes key information about phases and criticality, but the von Neumann
entropy is costly to access in experiments and simulations, often requiring full state
tomography. The second Rényi
entropy is readily measured using two-copy protocols and is often used as a proxy for the von Neumann
entanglement entropy, where it is assumed to track its asymptotic scaling. Sugino and Korepiny (Int. J. Mod. Phys. B 32, 1850306 (2018)) revealed that in the ground state of some highly constrained
spin models, the scaling of the von Neumann and Rényi
entropies can differ, varying from power law to logarithmic scaling as a function of the Rényi index. Here, we construct a number-conserving many-body state that demonstrates a Rényi-index-dependent change in the leading
entanglement scaling, generalizing previous results to the case of interacting
fermions. We introduce a
symmetry-aware lower bound on the von Neumann
entropy built from charge-resolved Rényi
entropies that can provide a protocol for diagnosing anomalous
entanglement scaling from experimentally accessible data.
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