Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter

cond-mat Watch Condensed Matter

Thursday 20 November

Materials Science

Synthesis and optical characterization of Mn-doped ZnS nanocrystalline thin films prepared via chemical bath deposition

Himal Pokhrel and Urvashi Verma

Manganese-doped zinc sulfide nanocrystalline thin films were synthesized using a low-temperature chemical bath deposition and deposited on glass substrates for controlled durations using triethanolamine (TEA) as a complexing and capping agent. After deposition, the films were annealed at 200 degrees Celsius and characterized by X-ray diffraction (XRD), SEM, and UV-Vis spectroscopy. XRD patterns confirmed the formation of nanocrystalline cubic zinc blende ZnS with an average crystallite size of approximately 37 nm. Optical measurements revealed strong transparency in the visible region, blue-shifted absorption edges due to quantum confinement, and a band gap value of approximately 3.70 eV. Mn incorporation resulted in a slight red shift of the absorption edge, attributed to particle growth and sp-d exchange interactions. These results demonstrate that Mn doping modifies the optical response of ZnS while preserving its crystalline structure, suggesting its suitability for optoelectronic and photovoltaic applications.
Read the full abstract

Mesoscale and Nanoscale Physics

Ultrafast {\mu}eV-Precision Bandgap Engineering in Low-Dimensional Topological Insulators

Peng Tan, Yuantao Chen, Yuqi Zhang et al. (+14 more)

Precise and ultrafast control of electronic band structures is a central challenge for advancing quantum functional materials and devices. Conventional approaches–such as chemical doping, lattice strain, or external gating–offer robust stability but remain confined to the quasi-static regime, far from the intrinsic femto- to picosecond dynamics that govern many-body interactions. Here, using cryogenic transient reflectance spectroscopy, we realize dynamic bandgap engineering in the anisotropic topological insulator $\alpha$-Bi$_4$Br$_4$ with unprecedented micro-electron-volt ($\mu$eV) precision. The exceptional sensitivity arises from the cooperative action of long-lived topological carriers, stabilized by restricted bulk-to-edge scattering phase space, together with symmetry-resolved coherent phonons that modulate inter-chain hopping. These channels jointly modify Coulomb screening and interband transitions, enabling both gradual and oscillatory control of the electronic structure. Supported by first-principles and tight-binding theory, we further demonstrate a dual-pump coherent control strategy for continuous, mode-selective tuning of electronic energies with $\mu$eV accuracy. This framework paves the way for ultrafast on-demand band-structure engineering, pointing toward new frontiers in quantum optoelectronics, precision measurement in molecular and biological systems, and attosecond control of matter.
Read the full abstract

All authors Peng Tan, Yuantao Chen, Yuqi Zhang, Hanyan Cheng, Guoyu Xian, Ming Cheng, Minghong Sun, Jiaxin Yin, Feifan Wang, Yaxian Wang, Yanjun Liu, Mingyuan Huang, Zhiwei Wang, Yugui Yao, Sheng Meng, Li Huang, Yanan Dai

Mesoscale and Nanoscale Physics

Synthetic Spatiotemporal Plasmonic Vortices On Chip

Qian Chen, Shuoshuo Zhang, Guoyu Xian et al. (+10 more)

Spatiotemporal vortices are polychromatic modes that intertwine orbital angular momentum (OAM) in space and time. Here we introduce a new class of such vortices, spatiotemporal plasmonic vortices (STPVs), carrying nontrivial topological spin textures. They are generated by chronotopic interference of temporally delayed plasmonic eigen-vortices, where a $\pi$-phase dislocation in the space-frequency domain maps into a 2$\pi$ spiraling phase in space-time, with the resulting focus-defocus dynamics emulate U(1) gauge transitions. Using interferometric time-resolved photoemission electron microscopy (ITR-PEEM), we directly image their nanometer-attosecond (nano-atto) evolution and control vortex number and position. Quantum-path analysis of coherent two-photon photoemission (2PP) processes reveals the nonlinear plasmonic polarization fields and angular-momentum conservation, establishing STPVs as a platform for probing spatiotemporally structured quantum matter.
Read the full abstract

All authors Qian Chen, Shuoshuo Zhang, Guoyu Xian, Haoqiang Hu, Xiaohua Wu, Xiaofei Wu, Jer-Shing Huang, Chen-Bin Huang, Jin-Hui Zhong, Yuquan Zhang, Xiaocong Yuan, Changjun Min, Yanan Dai

Mesoscale and Nanoscale Physics

Phonon Dichroisms Revealing Unusual Electronic Quantum Geometry

Ding Li, Guoao Yang, Tao Qin et al. (+2 more)

The quantum geometry tensor, intrinsic geometric characteristics of electronic states, plays a crucial role in the various nontrivial electromagnetic phenomena in quantum materials. Here, we reveal that quantum geometry significantly modifies phonon dichroisms through electron-phonon interactions in solids that break time-reversal and spatial inversion symmetries. Specifically, the circular phonon dichroism is primarily dominated by the heat magnetic moments, while the linear phonon dichroism depends on the heat Drude weight, a thermal analog of band Drude weight. Furthermore, we establish the f-sum rule for the heat magnetic moment that facilitates its experimental detections. We demonstrate our key findings in an archetypal model system: ferromagnetic two-dimensional electron gases with Rashba spin-orbit coupling. Our work uncovers the quantum-geometric origin of common phonon dichroisms and predicts the detectable signature of the heat magnetic moment of electrons in solids.
Read the full abstract

All authors Ding Li, Guoao Yang, Tao Qin, Jianhui Zhou, Yugui Yao

Materials Science

Coherent high-velocity chiral magnons in the metallic altermagnet CrSb

Ashutosh K. Singh, Niclas Heinsdorf, Abraham A. Mancilla et al. (+8 more)

We report the collective magnetism of the metallic altermagnet CrSb. Magnetic susceptibility and polarized neutron diffraction measurements show that CrSb is a perfectly compensated Ising altermagnet below a Néel temperature of $T_N = 733(4)$ K. Inelastic neutron scattering experiments reveal coherent and highly-dispersive antiferromagnetic spin waves with large group velocities of 61(2) km s$^{-1}$ and 58(2) km s$^{-1}$ along the in-plane and out-of-plane directions, respectively. The observed magnon dispersions along high-symmetry directions of the Brillouin zone are well described by a minimal Heisenberg model up to third nearest neighbors of alternating antiferromagnetic and ferromagnetic character, $J_1 = 23(4)$ meV, $J_2 = -5.4(8)$ meV, $J_3 = 5.2(8)$ meV, and an Ising single-ion anisotropy term $D = 0.15(4)$ meV. We observe clear momentum space signatures of chiral spin splitting along the low-symmetry $\Gamma$-$L$ direction, characteristic of higher-order altermagnetic exchange interactions, the first such observation in a metallic altermagnet. These findings identify CrSb as a singular material: a metallic altermagnet in which coherent spin-split magnons persist well above room temperature, providing a compelling platform for spintronic applications.
Read the full abstract

All authors Ashutosh K. Singh, Niclas Heinsdorf, Abraham A. Mancilla, Jörn Bannies, Avishek Maity, Alexander I. Kolesnikov, Masaaki Matsuda, Matthew B. Stone, Marcel Franz, Jonathan Gaudet, Alannah M. Hallas

Soft Condensed Matter

Emergence of chiral multi-armed spirals in an open system of migrating cells under continuous cell supply

Masayuki Hayakawa, Biplab Bhattacherjee, Hidekazu Kuwayama et al. (+1 more)

Chirality organize living and active matter systems into striking collective states, yet the principles that govern chiral ordering in open systems, where elements are continuously added or removed, remain unclear. A mutant strain of Dictyostelium discoideum deficient in chemotaxis (KI cells) forms centimeter-scale, clockwise multi-armed spirals. Each arm is a traveling band produced by short-range alignment interactions and guided by a polar-ordered rotating core that encircles the cell source. A subtle clockwise bias in the single-cell migration is amplified by collective ordering into tissue-scale chirality. To uncover the minimal ingredients, we developed an open chiral Vicsek model and identified intrinsic chirality and continuous cell supply as the key factors. Our study establishes a general route by which weak microscopic chirality and sustained material flux generate macroscopic chiral order, offering new insight into chiral patterning in multicellular behaviors.
Read the full abstract

All authors Masayuki Hayakawa, Biplab Bhattacherjee, Hidekazu Kuwayama, Tatsuo Shibata

Materials Science

Elucidating the High-Pressure Phases of MAPbBr3 Using a Machine Learning Force Field

Rashid Rafeek V Valappil, Sayan Maity and Varadharajan Srinivasan

High-pressure phases of the hybrid perovskite MAPbBr3 have been investigated in detail using a novel machine learning force field (MLFF). MLFF simulations successfully reproduce the sequence of pressure-induced phase transitions from the $\alpha$ ($Pm\bar{3}m$) to the $\beta$ ($Im\bar{3}$) and finally the $\gamma$ ($Pnma$/$Pmn2_1$) phase. In the $\alpha$ phase, the simulations confirm the triple-well character of the potential energy surface for octahedral tilting shedding light into the local dynamic distortions. In the $\beta$ phase, our simulations reveal MA sublattice doubling yielding both orientationally disordered and ordered MA ions mirroring experimental observation. This mixed-order phase results from locally frustrated host-guest couplings arising from the in-phase octahedral tilt system ($a^+a^+a^+$). In the high-pressure $\gamma$ phase, we confirm the formation of polar and anti-polar domains, with the latter have higher lifetimes and persist for over 50 ps at pressures above 1.5 GPa. By elucidating the behavior of various phases of MAPbBr3, this work provides a fundamental understanding of how host-guest interactions and octahedral tilting govern the material's properties. Further, the importance of time scales and length scales in characterizing these phases is emphasized.
Read the full abstract

Mesoscale and Nanoscale Physics

Nature of 2D XY antiferromagnetism in a van der Waals monolayer

Cheol-Yeon Cheon, Volodymyr Multian, Kenji Watanabe et al. (+3 more)

Two-dimensional antiferromagnetism has long attracted significant interest in many areas of condensed matter physics, but only recently has experimental exploration become feasible due to the isolation of van der Waals antiferromagnetic monolayers. Probing the magnetic phase diagram of these monolayers remains however challenging because established experimental techniques often lack the required sensitivity. Here, we investigate antiferromagnetism in atomically thin van der Waals magnet NiPS3 using magnetotransport measurements in field-effect transistor devices. Temperature-dependent conductance and magnetoresistance data reveal a distinct magnetic behavior in monolayers as compared to thicker samples. While bilayer and multilayer NiPS3 exhibit a single magnetic phase transition into a zig-zag antiferromagnetic state driven by uniaxial anisotropy, monolayer NiPS3 undergoes two magnetic transitions, with a low-temperature phase governed by in-plane hexagonal magnetic anisotropy. The experimentally constructed phase diagram for monolayer NiPS3 matches theoretical predictions from the six-state clock and 2D-XY models incorporating hexagonal anisotropy.
Read the full abstract

All authors Cheol-Yeon Cheon, Volodymyr Multian, Kenji Watanabe, Takashi Taniguchi, Alberto F. Morpurgo, Dmitry Lebedev

Materials Science

Extending SLUSCHI for Automated Diffusion Calculations

Qi-Jun Hong, Qing Chen, Ligen Wang et al. (+6 more)

We present an extension of the SLUSCHI package (Solid and Liquid in Ultra Small Coexistence with Hovering Interfaces) to enable automated diffusion calculations from first-principles molecular dynamics. While the original SLUSCHI workflow was designed for melting temperature estimation via solid-liquid coexistence, we adapt its input and output handling to isolate the volume search stage and generate one production trajectory suitable for diffusion analysis. Post-processing tools parse VASP outputs, compute mean-square displacements (MSD), and extract tracer diffusivities using the Einstein relation with robust error estimates through block averaging. Diagnostic plots, including MSD curves, running slopes, and velocity autocorrelations, are produced automatically to help identify diffusive regimes. The method has been validated through representative case studies: self- and inter-diffusion in Al-Cu liquid alloys, sublattice melting in Li_7La_3Zr_2O_12 and Er_2O_3, interstitial oxygen transport in bcc and fcc Fe, and oxygen diffusivity in Fe-O liquids with variable Si and Al contents. Viscosity and diffusivity are linked through the Stokes-Einstein relation, with composition dependence assessed via simple linear mixing. This capability broadens SLUSCHI from melting-point predictions to transport property evaluation, enabling high-throughput, fully first-principles datasets of diffusion coefficients and viscosities across metals and oxides.
Read the full abstract

All authors Qi-Jun Hong, Qing Chen, Ligen Wang, Dallin Fisher, Audrey CampBell, Si-Da Xue, Linqin Mu, Noemi Leick, Seetharaman Sridhar

Materials Science

High-Throughput Exploration of Refractory High-Entropy Alloys for Strength and Plasticity

Stephen A. Giles, Hugh Shortt, Peter K. Liaw et al. (+1 more)

Refractory high-entropy alloys (RHEAs) are compositionally complex materials which have been demonstrated to have the potential for exceptional strength at high operating temperatures. However, their composition space is vast, and other property requirements, such as acceptable plasticity at room-temperature, must be met. Here, we leverage recently published, state-of-the-art deep learning models to predict compressive yield strength at 1,000 {\deg}C and room-temperature plasticity of >100,000 RHEAs. Multiple candidate materials were identified which exhibited exceptional balance between strength and plasticity. Upon experimental synthesis, multiple candidates were proven to outperform any previously reported RHEAs for simultaneous strength and plasticity. Our work demonstrates the power of data-driven approaches for rapid materials design, and enables continued multi-property optimization and materials discovery.
Read the full abstract

All authors Stephen A. Giles, Hugh Shortt, Peter K. Liaw, Debasis Sengupta

Mesoscale and Nanoscale Physics

A simple quantum dot: numerical and variational solutions

Connor Walsh, Ian MacPherson, Davidson Joseph et al. (+4 more)

We describe a simple quantum dot that consists of two crossed two-dimensional troughs. As such there is no potential well; nonetheless, this geometry gives rise to a bound state, centred on the point at which these troughs cross one another. This problem is interesting both because the existence of a bound state may surprise students and because it can be solved using a variety of computational techniques, including matrix mechanics, finite differences, and mode matching. We present these methods and show how the mode-matching method in this case provides the most accurate solution to the problem. Additionally, the mode-matching method can be used to generate a simple wave function that yields the lowest energy known to date to arise out of an analytical variational solution for this problem.
Read the full abstract

All authors Connor Walsh, Ian MacPherson, Davidson Joseph, Suyash Kabra, Ripanjeet Singh Toor, Mason Protter, Frank Marsiglio

Mesoscale and Nanoscale Physics · Cross-listed from physics.optics

Single-mode magnon-polariton lasing and amplification controlled by dissipative coupling

Zi-Qi Wang, Zi-Yuan Wang, Yi-Pu Wang et al. (+1 more)

We demonstrate single-mode lasing of magnon polaritons in a cavity magnonic system enabled by dissipative coupling between two passive modes, microwave cavity mode and magnon mode in a ferrimagnetic spin ensemble. The cavity mode is partially compensated through a feedback circuit, which reduces its linewidth but retains its dissipative nature. By tuning the compensation strength and dissipative coupling strength, we reach a system cooperativity of unity, marking the lasing threshold and the formation of a zero-linewidth polariton mode. This mode also corresponds to a perfect Friedrich-Wintgen bound state in the continuum. Further increase of the cooperativity drives the system into the strong dissipative coupling regime, where magnon polariton amplification arises between two real frequency scattering poles. These results reveal that dissipative coupling cooperativity carries a clear physical meaning and serves as a key parameter for controlling phase transitions. Dissipative coupling offers an alternative paradigm for tailoring light matter interactions, paving the way for advances in both information processing and quantum technologies.
Read the full abstract

All authors Zi-Qi Wang, Zi-Yuan Wang, Yi-Pu Wang, J. Q. You

Materials Science

Quantum Reorientational Excitations in the Raman Spectrum of Hydrogen

Philip Dalladay-Simpson, Eric Edmund, Huixin Hu et al. (+2 more)

Low-frequency Raman peaks, below 250 cm-1, are observed in hydrogen between 2-174 GPa and 13-300 K. The origin of these features is attributed to reorientational transitions (DeltaJ = 0; Q0-branch), which shift from the Rayleigh line as anisotropic intermolecular interactions lift the mJ degeneracy. This family of excitations closely follows the behavior of the S0-branches, sharing their dependence on pressure, temperature, and ortho-H2 concentration. Above 65 K, spectra corrected by the Bose-Einstein population factor reveal a broad continuum arising from populated higher J-states and increased ortho-para disorder. Upon entering phase III, where molecular rotation is inhibited, this continuum is quenched, giving way to well-established optical phonons. Below 25 K, equilibrated samples demonstrate a fine structure from isolated and pair excitations from impurity ortho-H2 molecules in a parahydrogen lattice, the latter a sensitive probe to anisotropic intermolecular interactions relevant to the quantum modeling of solid H2.
Read the full abstract

All authors Philip Dalladay-Simpson, Eric Edmund, Huixin Hu, Mario Santoro, Federico Aiace Gorelli

Mesoscale and Nanoscale Physics

Skyrmionium meta-matter: a topologically heterogeneous magnetic crystal with emergent hybrid dynamics

Andrey O. Leonov and Kaito Nakamura

We introduce and systematically investigate a new class of topological magnetic textures, skyrmionium meta-matter, composed of skyrmioniums (Skm, $Q=0$) and skyrmions (Sk, $Q=-1$) arranged in periodic lattices mimicking the richness of atomic materials. Pure skyrmionium lattices are unstable against elongation distortions and relax into the spiral phase, but even a small fraction of skyrmions acts as topological "pins" that stabilize diverse mixed Skm–Sk crystals. We classify these states by topological stoichiometry (Skm$_n$Sk$_m$) and show that each composition hosts multiple metastable polymorphs with distinct plane-group symmetries. Structural transformations between polymorphs are achieved by varying the lattice spacing, suggesting experimental control via pressure or strain. The collective spin dynamics is explored for both in-plane and out-of-plane AC magnetic fields. The resulting absorption spectra show resonant modes beyond the two rotational and one breathing mode of conventional skyrmion lattices. We identify hybrid excitations unique to Skm–Sk crystals, including (i) deformation-assisted rotations, where skyrmions acquire polygonal shapes and rotate, and (ii) orbital modes, where breathing skyrmioniums induce circular motion of confined skyrmions without changing their size. Mode frequencies span sub-GHz to above 10 GHz, consistent with exchange and DMI energy scales. Our results establish skyrmionium-based meta-matter as a versatile platform for tunable, topologically heterogeneous magnetic lattices with rich structural and dynamical properties, paving the way for reconfigurable magnonic and spintronic applications.
Read the full abstract

Mesoscale and Nanoscale Physics

Nonreciprocal spin wave in room-temperature van der Waals ferromagnet $(\rm Fe_{0.78}Co_{0.22})_{5}GeTe_{2}$

Guofu Xu, Feihao Pan, Jiyang Ou et al. (+7 more)

Here, we investigate the spin waves in room-temperature van der Waals ferromagnet $(\rm Fe_{0.78}Co_{0.22})_{5}GeTe_{2}$ by utilizing Brillouin light scattering technique. The spin wave dispersion in flakes of different thicknesses shows the key role of dipolar interaction in the spin waves of vdW ferromagnets, and the non-reciprocity of spin wave in thick flakes is observed, which is attributed to the bulk Dzyaloshinskii-Moriya interaction after excluding the influence of dynamic dipolar interaction. The measured bulk DMI parameter D is 0.08 $\rm mJ/m^2$, which is double that of pure $\rm Fe_5GeTe_2$. Our work shows that Co-doped $\rm Fe_5GeTe_2$ is a promising platform for investigating propagating spin wave and topological spin textures at room temperature.
Read the full abstract

All authors Guofu Xu, Feihao Pan, Jiyang Ou, Wenjun Ma, Xu Zhang, Xiling Li, Guoqiang Yu, Peng Cheng, Hongjun Xu, Guozhi Chai

Statistical Mechanics · Cross-listed from quant-ph

Universal work statistics in quenched gapless quantum systems

Donny Dwiputra, Mir Faizal, Francesco Marino et al. (+1 more)

We study the universality of work statistics performed during a quench in gapless quantum systems. We show that the cumulants of work scale separately in the fast and slow quench regimes, following a power law analogous to the universal scaling in the Kibble-Zurek mechanism for topological defect formation in phase transition. As an example, we analyze the nonequilibrium dynamics of a quenched Heisenberg XXZ chain at its critical gapless state using the bosonization picture, resulting in a Tomonaga-Luttinger liquid. The analytical scaling is in agreement with the exact numerical calculation for the fast and slow quench regimes. In finite systems, the characteristic function display an oscillatory pattern which disappears in the thermodynamic limit. This study is particularly useful for understanding the thermodynamics of adiabatic quantum computation.
Read the full abstract

All authors Donny Dwiputra, Mir Faizal, Francesco Marino, Freddy P. Zen

Superconductivity

Conventional superconductivity in single-crystalline BiPt

S. Sharma, M. Pula, Sajilesh K. P. et al. (+10 more)

Binary Bi-Pd/Pt systems have attracted a lot of interest because of their topologically non-trivial nature along with superconductivity. We report the structural and superconducting properties of high-quality single-crystalline BiPt using a comprehensive range of experimental techniques, including X-ray diffraction, electron microscopy, muon spin rotation/relaxation ({\mu}SR), magnetization, resistivity, and heat capacity. Our findings establish that BiPt is a weak type-II superconductor with a transition temperature (Tc) of 1.2 K which exhibits pronounced anisotropic superconducting characteristics attributed to its hexagonal crystal structure. Magnetization and electronic transport studies reveal that BiPt lies within the dirty limit, while {\mu}SR and heat capacity data indicate conventional s-wave superconductivity that maintains time-reversal symmetry. This work provides valuable insights into the pairing symmetry and superconducting mechanism of topologically trivial BiPt, a sound comparison system for other Bi-based topologically nontrivial superconductors.
Read the full abstract

All authors S. Sharma, M. Pula, Sajilesh K. P., J. Gautreau, B. S. Agboola, J. P. Clancy, J. E. Sonier, A. Ghara, S. R. Dunsiger, M. Greven, M. J. Lagos, A. Kanigel, G. M. Luke

Disordered Systems and Neural Networks

Noise-induced resonant acceleration of a charge in an intermittent magnetic field: an exact solution for ergodic and non-ergodic fluctuations

Gerardo Aquino and Mauro Bologna

We study the diffusion of a charged particle in a magnetic field subject to stochastic dichotomous fluctuations. The associated induced electric field gives rise to non-trivial dynamical regimes. In particular, when the mean magnetic field vanishes, the particle remains confined within a finite radius, regardless of the fluctuation statistics. For a non-zero mean field, we show, using a density approach for Poissonian fluctuations, that the particle undergoes an exponential regime of accelerated diffusion. Crucially and more generally, adopting a trajectory-based formalism, we derive an exact analytical solution valid for arbitrary waiting-time distributions, including non-Poissonian and non-ergodic cases. Even rare, abrupt field reversal are shown to trigger exponential acceleration of the particle's diffusion. We demonstrate that this behaviour stems from noise exciting resonance bands present for periodic fluctuations, and we propose noise-induced resonant acceleration as a robust and efficient charge acceleration mechanism, potentially more effective than Fermi's classic model for cosmic acceleration.
Read the full abstract

Quantum Gases

A low-energy effective Hamiltonian for Landau quasiparticles: I. A unified theory of transport and superfluidity in Fermi liquids

Pierre-Louis Taillat and Hadrien Kurkjian

We introduce a new renormalisation scheme to construct the Landau quasiparticles of Fermi fluids. The scheme introduces an energy cutoff $\Lambda$ to remove the resonant couplings, enabling the dressing of the particles into quasiparticles via a unitary transformation. The dynamics of the quasiparticles is then restricted to low-energy transitions and is fully determined by an effective Hamiltonian which unifies the Landau function $f$, the pair interaction $g$ responsible for superfluidity, and the collision amplitude $\mathcal{A}$ responsible for transport and equilibration. Studying the flow equation that results from infinitesimal variations of the cutoff, we recover the Bethe-Salpeter relation between $f$ and the forward limit of $\mathcal{A}$, and we demonstrate an analogue relation between $g$ and the frontal limit of $\mathcal{A}$. We show that our effective theory captures all the low-energy phenomena of Fermi liquids, from the equation of state to the transport properties, both in the normal and in the superfluid phase. We apply it to the calculation of non-Fermi liquid corrections to the quasiparticle lifetime. This publication is continued by arXiv:2607.07041 where we apply the effective theory to a Fermi fluid of ultracold atoms.
Read the full abstract

Wednesday 19 November

Statistical Mechanics · Cross-listed from q-bio.PE

Thermodynamics + Natural Selection = Bayesian Inference

Seth Lloyd

Consider a population of organisms that harvest free energy from their environment to reproduce. This paper shows that if the organisms' reproductive rates are proportional to the amount of physical free energy that they can convert into reproductive work, then the implicit probabilities that the organisms assign to environmental states are updated according to Bayes' rule.
Read the full abstract

Mesoscale and Nanoscale Physics · Cross-listed from quant-ph

Generation of spin-squeezed states using dipole-coupled spins

Yifan Song, Nabiha Hasan and Susumu Takahashi

Spins in solids and molecules are promising for applications of quantum sensing technology. The sensitivity of the quantum sensing depends on how precisely spin observables can be determined in the measurement, and is intrinsically limited by the uncertainties of the observables. The use of a spin-squeezed state in a quantum sensor can reduce the uncertainty below the standard quantum limit when combined with an appropriate measurement procedure. Here, we discuss the simulation study of the generation of a squeezed state in an interacting spin system. We show that a spin system coupled by the magnetic dipole interaction can create a squeezed state. Model systems to realize the spin squeezing experimentally are also discussed. In addition, we find that a squeezed state is a type of entangled state. The present work paves the way to realize a squeezed state using a spin system to build a quantum sensor network with improved sensitivity, and to use it for the detection of quantum entanglement.
Read the full abstract

Mesoscale and Nanoscale Physics

Nonlocal Transport in Cr-doped (Bi,Sb)2Te3: Absence of Nonchiral Edge States

Valery Ortiz Jimenez, Paul M. Haney, Farzad Mahfouzi et al. (+3 more)

The quantum anomalous Hall effect shows great promise for realization of the ohm without the need for an external magnetic field. The most mature material platform is magnetically doped topological insulators. In these materials, precise quantization is limited to low temperatures, with the activation energy for dissipative transport typically in the range of 1 K. One potential source of dissipative transport is non-chiral edge states. These states are expected to be present in sufficiently thick samples. In this work, we perform extensive Hall and non-local resistance measurements in a Hall bar geometry at 2 K. By comparing 15 independent transport measurements to different transport models, we find that the system behavior is well-described by a simple continuum Ohm's law model. The addition of non-chiral edge states into the model does not significantly improve the fitting, and we conclude that there is not strong evidence for these states. We discuss the implications of our results for the prospect of high temperature quantized anomalous Hall effect in these materials.
Read the full abstract

All authors Valery Ortiz Jimenez, Paul M. Haney, Farzad Mahfouzi, Ngoch Thanh Mai Tran, Albert F. Rigosi, Curt A. Richter

Mesoscale and Nanoscale Physics

Selective Shuttling of Electrons on Helium Using a CMOS Control Platform

K. E. Castoria, H. Byeon, N. R. Beysengulov et al. (+5 more)

Electrons bound to the surface of liquid helium are an emerging quantum computing platform, offering the potential for highly mobile spin qubits that can be manipulated using CMOS-fabricated devices. Here, as a step toward realizing this technology, we demonstrate selective two-dimensional shuttling of electrons across a helium film condensed on the surface of a CMOS control chip. The electrons are moved in packets containing, on average, several tens down to single electrons. We perform CCD-style electron shuttling in any of 128 transport microchannels, each of which links electron storage zones and sensing zones in the 2D plane. Shuttling sequences can be repeated at least 10$^9$ times with no detectable electron loss. The device serves as a prototype quantum information processing platform that is readily scalable to control large monolithically integrated arrays of single electron spins.
Read the full abstract

All authors K. E. Castoria, H. Byeon, N. R. Beysengulov, E. O. Glen, M. Sammon, J. Pollanen, D. G. Rees, S. A. Lyon

Statistical Mechanics

Boltzmann-Kolmogorov equation

Mário J. de Oliveira

We investigate the properties of a Kolmogorov equation governing the time evolution of the probability distribution defined in phase space. Energy is strictly conserved along a trajectory in phase space, meaning the equation is appropriate to describe an isolated system, and the stationary state is the Gibbs microcanonical distribution. The equation predicts the increase in entropy in agreement with thermodynamics, and in contrast with the Liouville equation, which conserves entropy. Using an approximation in which the distribution is a product of one-particle distributions, we derive the Boltzmann equation of kinetic theory. We also consider a Kolmogorov equation to describe an open system in contact with the external environment. In this case the equation describes not only the situation in which the system is found in thermodynamic equilibrium with a Gibbs canonical distribution in the stationary state, but also the nonequilibrium steady state with a continuous production of entropy.
Read the full abstract

Statistical Mechanics · Cross-listed from math.QA

Universal TT- and TQ-relations via centrally extended q-Onsager algebra

Pascal Baseilhac, Azat M. Gainutdinov and Guillaume Lemarthe

Let $A_q$ be the alternating central extension of the q-Onsager algebra, a comodule algebra over the quantum loop algebra of $sl_2$. We classify one-dimensional representations of $A_q$, and show that spin-j K-operators constructed in arXiv:2301.00781 act as K-matrices previously obtained in the literature. Using these K-operators and K-matrices, we construct universal spin-j transfer matrices generating commutative subalgebras in $A_q$. Within a technical conjecture, we derive their fusion hierarchy, the so-called universal TT-relations. On spin-chain representations of $A_q$, we show how the universal transfer matrices evaluate to spin-chain transfer matrices, and as a result we get explicit TT-relations for all values of spins for auxiliary and quantum spaces, any inhomogeneities, and general integrable boundary conditions. In particular, we derive previously conjectured TT-relations. Using the TT-relations, we show that n-th local conserved quantities of the spin-j chains of length N are polynomials of total degree 4Njn in two non-local operators of the q-Onsager algebra. As a result, we give an algorithm of explicit calculation of all local conserved quantities in terms of spin operators. Furthermore, using the universal TT-relations we derive exchange relations between spin-j Hamiltonians and the two non-local operators showing non-trivial symmetries for special boundary conditions, that they commute with all Hamiltonian densities. As another application of our universal TT-relations we propose universal T-system, Y-system and universal TQ-relations for $A_q$, and as a result, universal TQ for the q-Onsager algebra. For diagonal boundary conditions, we also obtain universal TT- and TQ-relations for a degenerate version of $A_q$ known as centrally extended augmented q-Onsager algebra. We finally discuss implications of our results for generalized Gibbs ensemble construction.
Read the full abstract

Statistical Mechanics

Effects of Non-reciprocity on Coupled Kuramoto Oscillators

Shaon Mandal Chakraborty, Bibhut Sahoo, Peter Sollich et al. (+1 more)

All the fundamental interactions (such as gravity or electromagnetic interactions) are reciprocal in nature. However, in the macroscopic world, in particular outside equilibrium, non-reciprocal or non-mutual interactions are quite ubiquitous. Understanding the impact of such non-reciprocal interactions has drawn a significant amount of interest in physics and other fields of sciences in recent years. We explore a non-reciprocal version of coupled oscillators (known as the Kuramoto model) with the aim of understanding the role of non-reciprocity, particularly in relation to chimera states, where oscillators spontaneously break into mutually synchronous and asynchronous groups. Our findings suggest that non-reciprocity not only alters the state diagram of the chimera state significantly but can also lead to new dynamical states, such as traveling chimera, run-and-chase and coexistence phases.
Read the full abstract

All authors Shaon Mandal Chakraborty, Bibhut Sahoo, Peter Sollich, Rituparno Mandal

Mesoscale and Nanoscale Physics

Effects of high-order Van Hove singularities on exciton and trion energy dispersions

Lewis J. Burke, Mark T. Greenaway and Joseph J. Betouras

We investigate the effects of Van Hove singularities in the electronic band structure of two-dimensional semiconductors on the energy dispersion of excitons and positive trions. In particular, we study valence band energy dispersions which possess (i) a typical logarithmic Van Hove singularity, (ii) a line high-order Van Hove singularity (HOVHS) from a Mexican-hat dispersion or (iii) a point HOVHS such as a monkey saddle. We find that the density of states (DOS) of excitons and trions containing such singularities is dramatically enhanced and shows, in general, how the HOVHS in the valence band can strongly affect and be mirrored in the DOS of excitons and trions. This leads to new states that govern the optical properties of the system. In addition, we study a set of materials, InSe, GaSe and $\alpha$-SnAs, from a class of materials in which the topmost valence band has an inverted Mexican-hat shape. The most favourable exciton occurs when the singularity is at the $\Gamma$-point, as in the example of monolayer $\alpha$-SnAs, which hosts a HOVHS. Our work thus provides a pathway to engineer specific bound states in two-dimensional materials that host such singularities, thereby opening new avenues for potential applications.
Read the full abstract

Strongly Correlated Electrons

Magnetostriction in the $J$-$K$-$\Gamma$ model: Application of the numerical linked cluster expansion

Alexander Schwenke and Wolfram Brenig

We apply the numerical linked cluster expansion (NLCE) to study thermodynamic properties of the proximate Kitaev magnet $\alpha$-RuCl$_3$ on the honeycomb lattice in the presence of a magnetic field. Using the extended spin-1/2 $J$-$K$-$\Gamma$ model and based on documented exchange and magnetoelastic coupling parameters, we present results for the internal energy, the specific heat, and the magnetization. Moreover, the linear magnetostriction coefficient perpendicular to the plane is calculated, which is sensitive to changes of the in-plane spin-spin correlations. We find the magnetostriction to display a dip-like feature, in line with the temperature dependent and field-driven suppression of magnetic order in $\alpha$-RuCl$_3$. Our results are consistent with previous findings, establishing NLCE also as a tool to study magnetoelastic features of quantum magnets.
Read the full abstract

Quantum Gases · Cross-listed from quant-ph

Engineering multi-mode bosonic squeezed states using Monte-Carlo optimization

Jieqiu Shao, Diego A. R. Dalvit, Lukasz Cincio et al. (+1 more)

Bosonic systems, such as photons and ultracold atoms, have played a central role in demonstrating quantum-enhanced sensing. Quantum entanglement, through squeezed and GHZ states, enables sensing beyond classical limits. However, such a quantum advantage has so far been confined to two-mode bosonic systems, as analogous multi-mode squeezed states are non-trivial to prepare. Here, we develop a Monte-Carlo based optimization technique which can be used to efficiently engineer a Hamiltonian control-sequence for multi-mode bosonic systems to prepare multi-mode squeezed states. Specifically, we consider a Bose-Einstein condensate in an optical lattice, relevant for applications in gravimetry and gradiometry, and demonstrate that metrologically useful squeezed states can be generated using the Bose-Hubbard Hamiltonian which includes on-site atomic interactions, tunable via Feshbach resonances. By analyzing the distribution (density) of the quantum Fisher information (QFI) over the Hilbert space, we identify a characteristic intermediate scaling of the QFI: $\mathcal{O}(N^2 L+L^2 N)$, which lies between the standard quantum limit (SQL) and the Heisenberg limit (HL) for $N$ atoms in $L$ modes. We show that in general, within the Hilbert space there is a finite, $\mathcal{O}(1)$ measure subset of Hilbert space with an intermediate QFI scaling. Therefore, one can find a Hamiltonian control sequence using a Monte Carlo optimization over random control sequences, that produces a state with intermediate scaling of the QFI. We assume an experimentally accessible range of the control parameters in the Hamiltonian resources and show that the intermediate scaling can be readily achieved. Our results indicate that the HL can be approached in quantum gravimetry using realistic experimental parameters for systems with $L=\mathcal{O}(1)$ and $N\gg L$.
Read the full abstract

All authors Jieqiu Shao, Diego A. R. Dalvit, Lukasz Cincio, Bharath Hebbe Madhusudhana

Mesoscale and Nanoscale Physics

Floquet Bosonic Kitaev Chain

Raditya Weda Bomantara

We propose a class of periodically driven (Hermitian) modified bosonic Kitaev chains that effectively hosts rich nonHermitian Floquet topological phenomena. Two particular models are investigated in details as case studies. The first of these represents a minimal topologically nontrivial model in which nonHermitian skin effect, topological zero modes, and topological $\pi$ modes coexist. The other displays a more sophisticated model that supports multiple topological zero modes and topological $\pi$ modes in a tunable manner. By subjecting both models to perturbations such as a finite onsite bosonic frequency and spatial disorder, these features exhibit distinct responses. In particular, while generally all topological edge modes are robust against such perturbations, the nonHermitian skin effect is easily suppressed and revived by, respectively, the onsite bosonic frequency and spatial disorder in the first model, but it could be insensitive to both perturbations in the second model. Our studies thus demonstrate the prospect of a periodically driven bosonic Kitaev chain as a starting point in exploring various nonHermitian Floquet topological phases through the lens of a Hermitian system.
Read the full abstract