Materials Science · Cross-listed from physics.comp-ph
Parallel and GPU accelerated code for phase-field and reaction-diffusion simulations
Steven A. Silber and Mikko Karttunen
We present SymPhas 2.0, a major update of the compile-time symbolic
algebra simulation framework SymPhas for phase-field and reaction-
diffusion models. This release introduces significant expansions and enhancements that enable the definition of a phase-field model directly from the free-energy functional via compile-time evaluated functional differentiation. It also introduces directional derivatives, symbolic summation, tensor-valued expressions, and compile-time derived finite difference stencils of arbitrary order and accuracy. Furthermore, the code has been parallelized for CPUs with MPI, and GPU computing has been added using CUDA (Compute Unified Device Architecture). For the latter, symbolic expressions are compiled into optimized CUDA kernels, allowing large-scale simulations to execute entirely on the GPU. For large systems ($32,768^2$ in 2D and $1,024^3$ in 3D with double precision), speedups up to $\sim \!\!1,000 \times$ were obtained compared to the first version of SymPhas using multi-threaded CPU execution on a single system. These developments establish SymPhas 2.0 as a flexible and scalable framework for efficient implementation of phase-field and reaction-
diffusion models on GPU-based high-performance computing platforms.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Frequency Spectra of Isolated Laser Pulse Envelopes
L. H. Ford and Brian Fu
This paper will deal with isolated
laser pulses, those which last for a finite time interval and whose envelope function is strictly zero outside of this interval. We numerically calculate the
Fourier transform of this function and study its asymptotic behavior at high frequencies. This work is motivated by recent results on the probability distributions of quadratic operators in second quantized systems. An example is the density of a material which is subject to zero point fluctuations in the
phonon vacuum state. These distributions can decrease very slowly, leading to a relatively high probability for large fluctuations. If the operator is measured by a
laser pulse, the rate of decrease of the distribution mirrors the rate of decrease of the pulse envelope
Fourier transform. We describe a model for the creation of isolated pulses in which this
Fourier transform falls as an exponential of a fractional power of frequency and find examples where this fraction is in the range 0.1 to 0.2. The probability distribution for large fluctuation has the same functional form and implies a significant probability for fluctuations very large compared to the variance.
Read the full abstract ▾
Strongly Correlated Electrons
From One to Two Dimensions: Magnetic Phases in Weakly Coupled Spin Ladders
Mateo Cárdenes Wuttig and Andrew J. Millis
A large variety of materials can be approximately described by means of
spin-1/2 Heisenberg ladders. Here, the Density
Matrix Renormalization Group (DMRG)
algorithm together with a previously established numerical self-consistent mean-field approximation is used to investigate the
magnetic properties of
spin ladders coupled in a second dimension. The full ground state phase diagram including
spin-gapped,
antiferromagnetic, ferrimagnetic and fully polarized phases is presented as a function of interladder and intraladder coupling and
magnetic field. Measurement of the dependence of magnetization on applied
magnetic field is shown to enable location of a material on the phase diagram and determination of the
Hamiltonian parameters. These results provide a practical route toward identifying and characterizing
magnetic materials composed of coupled
spin ladders.
Read the full abstract ▾
Quantum Gases
Tuning the Critical Current in Toroidal Superfluids via Controllable Impurities
K. Xhani, G. Del Pace, N. Grani et al. (+4 more)
We combine numerical and experimental approaches to study how
impurities affect the maximum superflow in an annular Bose-Einstein condensate. By tuning the
impurity density, we achieve precise control over the stability of persistent currents which increases with the
impurity number. In the unstable regime, the complex
vortex motion within the
impurity landscape, characterized by pinning and unpinning events, governs the timescale of the current decay and its final value. Our work establishes atomic superfluids as a pristine platform for exploring universal mechanisms of superflow stabilization and decay, paving the way for atomtronic
quantum technologies.
Read the full abstract ▾
All authors K. Xhani, G. Del Pace, N. Grani, D. Hernández-Rajkov, B. Donelli, G. Roati, L. Pezzè
Strongly Correlated Electrons
Matías G. Gonzalez and Johannes Reuther
The tetratrillium
lattice has recently been proposed as responsible for the dynamical properties observed in the $S=1$ langbeinite compound K$_2$Ni$_2$(SO$_4$)$_3$. Here, we study in detail the classical
spin liquid properties of this
lattice of tri-coordinated tetrahedra using classical Monte Carlo and large-$N$ theory calculations. In the large-$N$ limit, we find that the system presents a gapped spectrum with flat bottom bands, giving rise to a fragile
spin liquid with exponentially decaying correlations according to the classification of classical
spin liquids. We confirm that this scenario also holds in the more realistic Ising and Heisenberg cases, for which the system does not exhibit any finite-temperature phase transition, and the low-temperature
spin structure factors exhibit excellent quantitative agreement with the large-$N$ theory. We also provide insight into the
quantum $S=1/2$ limit by performing pseudo-Majorana functional renormalization group calculations at finite temperatures, and discuss the possible phases that can arise in the ground state due to
quantum fluctuations.
Read the full abstract ▾
Materials Science
Relaxation approach to quantum-mechanical modeling of ferroelectric and antiferroelectric phase transitions
Nikhilesh Maity, Sergey Lisenkov, Arlies Valdespino et al. (+5 more)
Ferroelectrics and antiferroelectrics are the electric counterparts of ferromagnets and antiferromagnets. These materials undergo temperature- and electric-fieldinduced phase transitions that give rise to their characteristic hysteresis loops. Modeling such hysteresis loops and associated phase transitions enables both a deeper fundamental understanding and reliable property predictions for this important class of materials. To date, modeling has largely relied on classical approaches, often remaining qualitative and/or empirical. Traditional interpretation of these transitions rests on two assumptions: (i) they are activated Arrhenius-type processes and (ii) they occur well within the classical regime. Here, we demonstrate that a model can instead be built on two \orthogonal" assumptions: (i) the phase transitions are relaxational processes and (ii) they require a
quantum mechanical treatment. Applying this model to both antiferroelectrics and ferroelectrics overcomes the limitations of traditional models and enables efficient first-principles simulations of phase transitions. The success of our unconventional approach highlights the significance of
quantum mechanics in transitions long regarded as purely classical. We anticipate that this framework will be applicable to a broad range of phase transitions, including
magnetic, elastic, multiferroic, and electronic, along with modeling of
quantum tunneling, rates of chemical reactions, and others.
Read the full abstract ▾
All authors Nikhilesh Maity, Sergey Lisenkov, Arlies Valdespino, Milan Haddad, Lewys Jones, Amit Kumar, Nazanin Bassiri-Gharb, Inna Ponomareva
Mesoscale and Nanoscale Physics
Broadband nonlinear Hall response and multiple wave mixing in a room temperature altermagnet
Soumya Sankar, Xingkai Cheng, Xinyu Chen et al. (+10 more)
Crystalline
symmetries determine the linear and nonlinear response of materials to external stimuli such as mechanical pressure and electromagnetic fields, governing phenomena such as piezoelectricity, optical activity, and multiple wave mixing with wide ranging technological applications. Altermagnets present a new class of materials with
magnetic crystalline order where specific
crystal symmetry operations connect
antiferromagnetic sublattices, leading to non-relativistic
spin-splitting of the electronic band structure. Hence, the electric material properties of altermagnets should uniquely mirror these underlying
symmetry properties, potentially giving rise to novel phenomena in response to external driving fields. Here, we report the discovery of a broadband third-order nonlinear anomalous
Hall effect in altermagnetic CrSb at room temperature. The comparison of our observations with
symmetry analyses and model calculations shows that this nonlinear
Hall response is induced by the nonlinear electric susceptibility of a Berry
curvature quadrupole, which exists within the
spin-split band structure of CrSb and is characterized by the underlying crystalline and
magnetic symmetries. We then utilize this third-order nonlinear electric susceptibility of CrSb to realize a multiple wave mixing device with pronounced four wave mixing output, which could, in principle, be extended to THz frequencies. Our study discovers that the crystalline
magnetic order of altermagnets determines their nonlinear electric material properties, which could facilitate applications in high-frequency electronics, THz generation, communication networks, and energy harvesting.
Read the full abstract ▾
All authors Soumya Sankar, Xingkai Cheng, Xinyu Chen, Xizhi Fu, Takahiro Urata Wataru Hattori, Wenlong Lu, Zihan Lin, Dong Chen, Claudia Felser, Hiroshi Ikuta, Junzhang Ma, Junwei Liu, Berthold Jäck
Mesoscale and Nanoscale Physics
Elastic Dislocation-based Skyrmion Traps: Fundamentals and Applications
Martín Latorre, Joaquín Barra, Juan Pablo Vera et al. (+4 more)
Topologically secure
spin configurations, such as skyrmions and bimerons, offer a compelling alternative to conventional
magnetic domains, potentially enabling high-density, low-power spintronic devices. These pseudo-particles, characterized by their swirling
spin textures and nontrivial topological charges, are prevalent and notably influence their electronic,
magnetic, and mechanical traits. This paper provides an in-depth overview of the interaction between a screw dislocation within a distorted
magnetic lattice, exploring possible coupling mechanisms and establishing a promising link between two disparate topics in materials science: topological magnetism and topological elasticity. We first provide a classical analysis of skyrmion motion that reveals the dislocations as shallow traps on the
magnetic texture. Afterwards, we provide an analysis of the quantized motion of the skyrmion and identify its
quantum states. We conclude by illustrating how the ideas in our paper can be implemented in simple yet compelling devices based on the shallow traps from an array of dislocations acting as frets in a race-track, controlling the motion with a low current activation mechanism.
Read the full abstract ▾
All authors Martín Latorre, Joaquín Barra, Juan Pablo Vera, Joaquín Martinez, Mario Castro, Sebastián Allende, Alvaro S. Nunez
Materials Science
Time-resolved observation of magnon splitting into vortex gyration and Floquet spin waves
T. Devolder, R. Lopes Seeger, C. Heins et al. (+9 more)
Forced excitations at frequencies in the range of the first order azimuthal
spin waves of a
magnetic disk in the
vortex state are known to scatter into the
vortex gyration mode, thereby allowing the growth of Floquet
spin waves forming a frequency comb. We study the temporal emergence of this dynamical state using time-resolved microwave electrical measurements. The most intense Floquet mode emerges synchronously with the gyration mode after a common incubation delay which diverges at the scattering threshold. This delay is minimal when the drive is resonant with one of the first order azimuthal
spin waves. It can be as short as 3 ns for the maximum investigated power. We conclude that the first-to-occur scattering mechanism is the three-wave splitting of a regular azimuthal eigenmode into a coherent pair formed by a gyration
magnon and a Floquet
spin wave.
Read the full abstract ▾
All authors T. Devolder, R. Lopes Seeger, C. Heins, A. Jenkins, L. C. Benetti, A. Schulman, R. Ferreira, G. Philippe, C. Chappert, H. Schultheiss, K. Schultheiss, J.-V. Kim
Mesoscale and Nanoscale Physics · Cross-listed from math-ph
Splitting obstructions and $\mathbb{Z}_2$ invariants in time-reversal symmetric topological insulators
Alessandro Ferreri, Domenico Monaco and Gabriele Peluso
The Fu-Kane-Mele $\mathbb{Z}_2$ index characterizes two-dimensional time-reversal symmetric topological phases of matter. We shed some light on some features of this index by investigating projection-valued maps endowed with a fermionic time-reversal
symmetry. Our main contributions are threefold. First, we establish a decomposition
theorem, proving that any such projection-valued map admits a splitting into two projection-valued maps that are related to each other via time-reversal
symmetry. Second, we provide a complete homotopy classification
theorem for these maps, thereby clarifying their topological structure. Third, by means of the previous analysis, we connect the Fu-Kane-Mele index to the Chern number of one of the factors in the previously-mentioned decomposition, which in turn allows to exhibit how the $\mathbb{Z}_2$-valued topological obstruction to constructing a periodic and smooth Bloch frame for the projection-valued map, measured by the Fu-Kane-Mele index, can be concentrated in a single pseudo-periodic Kramers pair.
Read the full abstract ▾
Superconductivity
In-Plane Differentiation and Out-of-Plane Coherence in Superconducting K$_{2-x}$Fe$_{4+y}$Se$_5$
Chih-Han Wang, Wu Phillip M, Gwo-Tzong Huang et al. (+2 more)
The structural link between superconductivity and anomalous $d_2$ diffraction signatures in K$_{2-x}$Fe$_{4+y}$Se$_5$ remains unresolved. Their appearance is accompanied by pronounced host-
lattice evolution rather than a static structural background. Using high-resolution synchrotron X-ray diffraction, we show that excess Fe alters the vacancy-ordered host
lattice, with structural differences between superconducting and nonsuperconducting states emerging before the $d_2$ features appear. All observed $d_2$ reflections can be described using two characteristic in-plane spacings and a nearly common low-temperature $c$ parameter. Temperature-dependent measurements reveal that superconductivity is associated with persistent in-plane differentiation and enhanced Fe-layer coherence along the $c$ axis. These results establish host-
lattice evolution as the common structural origin linking the $d_2$ family and superconductivity, and suggest that the host-
lattice differentiation identified here represents a structural analogue of the
symmetry redistribution in FeSe.
Read the full abstract ▾
All authors Chih-Han Wang, Wu Phillip M, Gwo-Tzong Huang, Ming-Jye Wang, Maw-Kuen Wu
Mesoscale and Nanoscale Physics
Exploring the Role of Interfacial Dzyaloshinskii-Moriya Interaction in Write Error Rate Anomalies of Spin-Transfer Torque Magnetic Tunnel Junctions
Prosenjit Das, Md Mahadi Rajib and Jayasimha Atulasimha
The performance and reliability of
spin-transfer torque
magnetic random-access
memory (STT-MRAM) can be compromised by anomalous switching behavior, especially during high-speed operations. One such anomaly, known as the "ballooning effect" is characterized by an unexpected non-monotonic increase in the write error rate (WER) with increase in STT current at specific current pulse durations. In this study, we systematically investigate the role of the interfacial Dzyaloshinskii-Moriya interaction (DMI) on such WER anomaly using micromagnetic simulations of 20 nm and 50 nm
magnetic tunnel junctions (MTJs). We show that DMI promotes incoherent magnetization reversal, prolongs the switching time and creates intermediate multidomain states that result in incomplete reversal. At high DMI values, these states persist even under large switching current densities, reproducing ballooning-like anomalies reported experimentally. In contrast, longer pulses overcome these effects by allowing the system sufficient time to reach a stable state. Our findings show that interfacial DMI can play a role in the ballooning effect and point to interfacial engineering as a practical strategy for improving the reliability of next-generation STT-MRAM.
Read the full abstract ▾
Soft Condensed Matter
Routes to the density profile and structural inconsistency
S. M. Tschopp, H. Vahid and J. M. Brader
Classical density functional theory (DFT) is the primary method for investigations of inhomogeneous fluids in external fields. It requires the excess Helmholtz free energy functional as input to an Euler-Lagrange equation for the one-body density. A variant of this methodology, the force-DFT, uses instead the Yvon-Born-Green equation to generate density profiles. It is known that the latter are consistent with the virial route to the thermodynamics, while DFT is consistent with the compressibility route. In this work we will show an alternative DFT scheme using the Lovett-Mou-Buff-Wertheim (LMBW) equation to obtain density profiles, that are shown to be also consistent with the compressibility route. However, force-DFT and LMBW DFT can both be implemented using a closure relation on the level of the two-body correlation functions. This is proven to be an advantageous feature, opening the possibility of an optimisation scheme in which the structural inconsistency between different routes to the density profile is minimized. (Structural inconsistency is a generalization of the notion of thermodynamic inconsistency, familiar from bulk integral equation studies.) Numerical results are given for the density profiles of two-dimensional systems of hard-core Yukawa particles with a repulsive or an attractive tail, in planar geometry.
Read the full abstract ▾
Statistical Mechanics
Chromatic Zeros on the Limit $G^{(p,\ell)}_\infty$ of the Family $G^{(p,\ell)}_m$ of Hierarchical Graphs
Shu-Chiuan Chang and Robert Shrock
We calculate the continuous accumulation set ${\cal B}_q(p,\ell)$ of zeros of the chromatic
polynomial $P(G^{(p,\ell)}_m,q)$ in the limit $m \to \infty$, on a family of graphs $G^{(p,\ell)}_m$ defined such that $G^{(p,\ell)}_m$ is obtained from $G^{(p,\ell)}_{m-1}$ by replacing each edge (i.e., bond) on $G^{(p,\ell)}_m$ by $p$ paths each of length $\ell$ edges, starting with the tree graph $T_2$. Our method uses the property that the chromatic
polynomial $P(G,q)$ of a graph $G$ is equal to the $v=-1$ evaluation of the partition function of the $q$-state Potts model, together with (i) the property that $Z(G^{(p,\ell)}_m,q,v)$ can be expressed via an exact closed-form real-space renormalization (RG) group transformation in terms of $Z(G^{(p,\ell)}_{m-1},q,v')$, where $v'=F_{(p,\ell),q}(v)$ is a rational function of $v$ and $q$ and (ii) ${\cal B}_q(p,\ell)(v)$ is the locus in the complex $q$-plane that separates regions of different asymptotic behavior of the $m$-fold iterated RG transformation $F_{(p,\ell),q}(v)$ in the $m \to \infty$ limit. Thus, our results involve calculations of region diagrams in the complex $q$-plane showing the type of behavior that occurs in the $m \to \infty$ limit of the $m$-fold iterated RG transformation mapping $F_{(p,\ell),q}(v)$ starting with the initial value $v=v_0=-1$. Calculations are presented of the maximal point $q_c(G^{(p,\ell)}_\infty)$ at which the locus ${\cal B}_q$ crosses the real-$q$ axis, as well as several other points at which, depending on $p$ and $\ell$, the locus ${\cal B}_q$ crosses this axis. We give explicit results for a variety of $(p,\ell)$ cases and observe a number of interesting features. Calculations of the ground-state degeneracy of the Potts antiferromagnet at $q_c(G^{(p,\ell)}_\infty)$ are presented. This work extends a previous study with R. Roeder of the $(p,\ell)=(2,2)$ case to higher $p$ and $\ell$ values.
Read the full abstract ▾
Materials Science
Spin and lattice dynamics at the spin-reorientation transitions in the rare-earth orthoferrite Sm$_{0.55}$Tb$_{0.45}$FeO$_{3}$
R.M. Dubrovin, A.I. Brulev, N.R. Vovk et al. (+10 more)
Linear and non-linear couplings of
magnetic and
lattice excitations are at the heart of many fascinating magnetophononic phenomena observed in rare-earth orthoferrites, the distinctive feature of which is the tendency to
spin-reorientation transitions. Here we report the results of the experimental study of the
spin and
lattice dynamics in the Brillouin zone center of the rare-earth orthoferrite Sm$_{0.55}$Tb$_{0.45}$FeO$_{3}$ by using polarized infrared reflectivity and Raman scattering spectroscopic techniques. The obtained results were supported by the first-principles calculations, which allowed us to reliably identify the parameters of most infrared- and Raman-active
phonons. We reveal the
spin-reorientation transitions $\Gamma_{4}(G_{a}F_{c}) \overset{T_{1}}\longleftrightarrow \Gamma_{24}(G_{ac}F_{ac}) \overset{T_{2}}\longleftrightarrow \Gamma_{2}(G_{c}F_{a})$ at $T_{1} \simeq 220$ K and $T_{2} \simeq 130$ K and carefully studied the following
evolution of Raman scattering on
magnetic excitations at these transitions. Notably, the intermediate
magnetic structure $\Gamma_{24}$ displays an exceptionally broad temperature range $\Delta{T} = T_{1} - T_{2} \simeq 90$ K in mixed Sm$_{0.55}$Tb$_{0.45}$FeO$_{3}$ compared to pure rare-earth orthoferrites. We attribute this broadening of the intermediate phase to the modification of the magnetocrystalline anisotropy as a result of the inhomogeneous
magnetic structure caused by the random distribution of rare-earth $\mathrm{Sm}^{3+}$ and $\mathrm{Tb}^{3+}$ ions. We found neither change in the parameters of Raman-active $B_{1g}$
phonons nor the appearance of new
phonons induced by
spin-reorientation transitions, which have been reported in $\mathrm{SmFeO}_{3}$. We assume that our results provide a solid basis for more deeper understanding of magnetophononic phenomena in rare-earth orthoferrites.
Read the full abstract ▾
All authors R.M. Dubrovin, A.I. Brulev, N.R. Vovk, I.A. Eliseyev, N.N. Novikova, V.A. Chernyshev, A.N. Smirnov, V.Yu. Davydov, Anhua Wu, Liangbi Su, R.V. Mikhaylovskiy, A.M. Kalashnikova, R.V. Pisarev
Statistical Mechanics
Backbone three-point correlation function in the two-dimensional Potts model
Ming Li, Youjin Deng, Jesper Lykke Jacobsen et al. (+1 more)
We study the three-point correlation function of the backbone in the two-dimensional $Q$-state Potts model using the Fortuin–Kasteleyn (FK) representation. The backbone is defined as the biconnected skeleton of an FK cluster after removing all dangling ends and bridges. To circumvent the severe critical slowing down in direct Potts simulations for large $Q$, we employ large-scale Monte Carlo simulations of the O$(n)$ loop model on the hexagonal
lattice, which is regarded to correspond to the Potts model with $Q=n^2$. Using a highly efficient cluster
algorithm, we compute the universal three-point amplitude ratios for the backbone ($R_\text{BB}$) and FK clusters ($R_\text{FK}$). Our computed $R_\text{FK}$ exhibits excellent agreement with exact conformal field theory predictions, validating the reliability of our numerical approach. In the critical regime, we find that $R_\text{BB}$ is systematically larger than $R_\text{FK}$. Conversely, along the tricritical branch, $R_\text{BB}$ and $R_\text{FK}$ coincide within numerical accuracy, strongly suggesting that $R_\text{BB}=R_\text{FK}$ holds throughout this regime. This finding mirrors the known equality of the backbone and FK cluster fractal dimensions at tricriticality, jointly indicating that both structures share the same
geometric universality.
Read the full abstract ▾
All authors Ming Li, Youjin Deng, Jesper Lykke Jacobsen, Jesús Salas
Soft Condensed Matter
Flocking transition in phoretically interacting active particles with pinning disorder
Sagarika Adhikary, Arvin Gopal Subramaniam and Rajesh Singh
Recent studies in the collective behavior of active colloids have shown that a global polar order may emerge due to long-ranged chemo-repulsive interactions between them. Here, we report the role of pinning disorder in the flocking transition for such a system. To this end, we study the problem of chemically interacting active colloids with some fraction of the colloids randomly pinned over space such that they can only rotate while phoretically interacting with other particles. Using this model, we investigate the sustenance of global polar order in the presence of quenched spatial disorder. We quantify the flocking transition by studying the global polarization, and the role of finite-size effects. We find that in the crystallite flocking phase, even a small fraction of pinning can destroy spatial crystalline order, although polar order in the form of a
liquid phase is maintained. It is observed that polar order is sustained in a system with a higher pinning fraction if the long-ranged repulsive force is subsequently increased. However, in absence of chemo-repulsive forces between particles, polar order drastically decreases even with a smaller pinning fraction. Our work suggests that the flocking transition of active colloids can be controlled via "translationally inert" obstacles, that rotate but do not translate whilst interacting with the bulk.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Point defects and their dynamic behaviors in silver monolayer intercalated between graphene and SiC
Van Dong Pham, Arpit Jain, Chengye Dong et al. (+4 more)
Point defects give rise to sharp modifications in the structures and electronic properties of two-dimensional metals, offering an atomic-level platform for fundamental studies and potential applications. In this work, we investigate atomic-scale defects in a two-dimensional silver monolayer intercalated between epitaxial
graphene and SiC using scanning tunneling microscopy. Dark and bright defects are identified as vacancies or substitutional
impurities within the silver monolayer, each hosting a localized electronic state. Remarkably, under tunneling electron excitation at negative bias, the bright defects exhibit dynamic behaviors characterized by inelastic switching between two states. The switching can be reversibly controlled by the microscope tip, enabling the defects to function as atomic-scale two-level conductance switches. Analysis of defect switching reveals possible defect origins and the relationship between dark and bright defect species. Our findings establish a pathway to precise manipulation of defects in two-dimensional metals and uncover previously unexplored dynamics with potential use in nanoelectronics.
Read the full abstract ▾
All authors Van Dong Pham, Arpit Jain, Chengye Dong, Li-Syuan Lu, Joshua A. Robinson, Achim Trampert, Roman Engel-Herbert
Superconductivity
Microwave Dressed States and Vacuum Fluctuations in a Superconducting Condensate
Anoop Dhillon and A. Hamed Majedi
Microwave dressed states are found to emerge within the superconducting condensate when coupled to a quantized electromagnetic field due to
photon-Cooper pair
entanglement. The renormalized energy separation between these states exceeds the prediction of BCS theory, with the enhancement depending on the number of
photons and also arising from electromagnetic
vacuum fluctuations. Our work introduces an
equilibrium quantum model of microwave-enhanced superconductivity, expanding the theoretical description beyond Eliashberg's non-
equilibrium theory. We further demonstrate that the superconducting condensate exerts a back-action on the electromagnetic field, suppressing electric field fluctuations, including those from the
vacuum state. This result is consistent with Glauber and Lewenstein's field quantization in dielectric media.
Read the full abstract ▾
Materials Science · Cross-listed from cs.CE
Phase field modelling of cracking and capacity fade in core-shell cathode particles for lithium-ion batteries
Y. Tu, B. Wu and E. Martínez-Pañeda
Core-shell electrode particles are a promising morphology control strategy for high-performance lithium-ion batteries. However, experimental observations reveal that these structures remain prone to mechanical failure, with shell fractures and core-shell debonding occurring after a single charge. In this work, we present a novel, comprehensive computational framework to predict and gain insight into the failure of core-shell morphologies and the associated degradation in battery performance. The fully coupled chemo-mechano-damage model presented captures the interplay between mechanical damage and electrochemical behaviours, enabling the quantification of particle cracking and capacity fade. Both bulk material fracture and interface debonding are captured by utilising the phase field method. We quantify the severity of particle cracking and capacity loss through case studies on a representative core-shell system (NMC811@NMC532). The results bring valuable insights into cracking patterns, underlying mechanisms, and their impact on capacity loss. Surface cracks are found to initiate when a significantly higher lithium concentration accumulates in the core compared to the shell. Interfacial debonding is shown to arise from localised hoop stresses near the core-shell interface, due to greater shell expansion. This debonding develops rapidly, impedes lithium-ion transport, and can lead to more than 10% capacity loss after a single discharge. Furthermore, larger particles may experience crack branching driven by extensive tensile zones, potentially fragmenting the entire particle. The framework developed can not only bring new insight into the degradation mechanisms of core-shell particles but also be used to design electrode materials with improved performance and extended lifetime.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
k-Selective Electrical-to-Magnon Transduction with Realistic Field-distributed Nanoantennas
Andreas Höfinger, Andrey A. Voronov, David Schmoll et al. (+9 more)
The excitation and detection of propagating
spin waves with lithographed nanoantennas underpin both classical magnonic
circuits and emerging
quantum technologies. Here, we establish a framework for all-electrical propagating
spin-wave spectroscopy (AEPSWS) that links realistic electromagnetic drive fields to micromagnetic dynamics. Using finite-element (FE) simulations, we compute the full vector near-field of electrical impedance-matched, tapered coplanar and stripline
antennas and import this distribution into finite-difference (FD) micromagnetic solvers. This approach captures the
antenna-limited wave-vector spectrum and the component-selective driving fields (perpendicular to the static magnetisation) that simplified uniform-field models cannot. From this coupling, we derive how realistic current return paths and tapering shapes, k-weighting functions, for Damon-Eshbach surface
spin waves in yttrium-iron-garnet (YIG) films are, for millimetre-scale matched CPWs and linear tapers down to nanometre-scale
antennas. Validation against experimental AEPSWS on a $48\,nm$ YIG film shows quantitative agreement in dispersion ridges, group velocities, and spectral peak positions, establishing that the
antenna acts as a tunable k-space filter. These results provide actionable design rules for on-chip magnonic transducers, with immediate relevance for low-power operation regimes and prospective applications in
quantum magnonics.
Read the full abstract ▾
All authors Andreas Höfinger, Andrey A. Voronov, David Schmoll, Sabri Koraltan, Florian Bruckner, Claas Abert, Dieter Suess, Morris Lindner, Timmy Reimann, Carsten Dubs, Andrii V. Chumak, Sebastian Knauer
Statistical Mechanics
Stochastic Thermodynamics of Cooperative Biomolecular Machines: Fluctuation Relations and Hidden Detailed Balance Breaking
D. Evan Piephoff and Jianshu Cao
We examine a biomolecular machine involving a driven, observable process coupled to a hidden process in a kinetically cooperative manner. A
stochastic thermodynamics framework is employed to analyze a fluctuation
theorem for the first-passage time of the observable process under nonequilibrium steady-state conditions. Based on a generic kinetic model, we demonstrate that, along first-passage trajectories,
entropy production remains constant when the changes in
stochastic entropy and free energy of the machine are balanced, which corresponds to zero net hidden flux through the initial state
manifold. Under this condition, which we define quite generally, this first-passage time fluctuation
theorem can be established, with its violation serving as an experimentally detectable signature of hidden detailed balance breaking (which we subsequently characterize). In addition, using an enzymatic model, we show that the violation of our first-passage time fluctuation
theorem can be thought of as a consequence of the breakdown of local detailed balance in the steps linking coarse-grained states that correspond to the initial and intermediate state
manifolds. In the absence of hidden current, the fluctuation
theorem is restored, and a mesoscopic local detailed balance condition can be established, which has implications for the thermodynamic analysis of driven, coarse-grained systems. This work sheds significant light on the unique connections between
stochastic thermodynamic quantities and kinetic measurements in complex cooperative networks.
Read the full abstract ▾
Soft Condensed Matter
Nonlinear morphoelastic energy based theory for stimuli responsive elastic shells
Matteo Taffetani and Matteo Pezzulla
Large deformations play a central role in the shape transformations of slender active and biological structures. A classical example is the eversion of the Volvox embryo, which demonstrates the need for shell theories that can describe large strains, rotations, and the presence of incompatible stimuli. In this work, a reduced two-dimensional morphoelastic energy is derived from a fully nonlinear three-dimensional formulation. The resulting model describes the mechanics of naturally curved shells subjected to non-elastic stimuli acting through the thickness, thereby extending previous morphoelastic theories developed for flat plates to curved geometries. Two representative constitutive laws, corresponding to incompressible Neo-Hookean and compressible Ciarlet-Geymonat materials, are examined to highlight the influence of both
geometric and constitutive nonlinearities. The theory is applied to the eversion of open and closed spherical shells and to vesiculation processes in biological systems. The results clarify how compressibility,
curvature, and through-the-thickness kinematics govern snap-through and global deformation, extending classical morphoelastic shell models. The framework provides a consistent basis for analyzing large deformations in elastic and biological shells driven by non-mechanical stimuli.
Read the full abstract ▾
Materials Science
Out-of-Plane Nonlinear Orbital Hall Torque
Hui Wang, Xukun Feng, Jin Cao et al. (+5 more)
Despite recent advances in orbitronics, generating out-of-plane orbital torques essential for field-free deterministic switching of perpendicular magnetization remains a key challenge. Here, we propose a strategy to produce such unconventional torques across broad classes of materials, by leveraging the nonlinear orbital
Hall effect. We demonstrate that this nonlinear orbital response is dramatically amplified by topological band degeneracies, where it overwhelmingly dominates the
spin response even in systems with strong
spin-orbit coupling. These features are confirmed via a quantitative investigation of representative topological metals RhSi, YPtBi, and PbTaSe$_2$, by combining our theory with first-principles calculations. The resulting orbital torques substantially surpass those from linear mechanisms reported thus far. These findings propel the research of orbital transport into the nonlinear regime, broaden the scope of orbital source materials, and establish a new pathway towards high-performance orbitronic devices.
Read the full abstract ▾
All authors Hui Wang, Xukun Feng, Jin Cao, Huiying Liu, Weibo Gao, Cong Xiao, Shengyuan A. Yang, Lay Kee Ang
Statistical Mechanics · Cross-listed from hep-th
Work distribution and fluctuation theorem in AdS/CFT
Daichi Takeda
From the AdS/CFT dictionary, we derive a bulk dual of the work distribution defined by the two-point measurement on the boundary, yielding a bulk formulation of the Tasaki-Crooks fluctuation
theorem. We argue that this does not merely supply a
holographic prescription for the work distribution; it encodes the mean energy change and fluctuations of bulk real-time dynamics associated with the two-point measurement.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Modification of Hanle and polarization recovery curves under interplay of hopping and quantum measurement back action
A. L. Zibinskiy and D. S. Smirnov
The measurements of Hanle and polarization recovery effects for localized charge carriers are the basic tools for determining parameters of the
spin dynamics, such as strength of the hyperfine interaction, for example, in
quantum dots. We describe the dependence of the
spin polarization of localized electrons on transverse and longitudinal
magnetic fields taking into account the interplay between electron hopping and measurement back action. We show that these two have a qualitatively similar effect in the Faraday geometry, but compete in the Voigt geometry. This allows one to describe a broad range of the experimental results and study the fundamental effects of
quantum measurements.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Long-range propagating paramagnon-polaritons in organic free radicals
Sebastian Knauer, Roman Verba, Rostyslav O. Serha et al. (+5 more)
Materials are commonly distinguished by their
magnetic response into diamagnetic, paramagnetic, and magnetically ordered (ferro-, ferri-, and
antiferromagnetic) phases. Diamagnets and paramagnets lack spontaneous long-range order, whereas ordered magnets develop such order below their Curie or Néel temperature and support single
spin-wave excitations (
magnons).
Magnons have found applications in
radio-frequency technologies and computation, magneto-optics, and foundational
quantum experiments. Above the Curie/Néel temperature, long-range order is lost and the material transitions to a paramagnetic phase, with localised
spin alignment in small patches, producing paramagnons with only short-range propagation. Here we show that long-range coherence is preserved in the organic free radical 2,2,6,6-tetramethylpiperidin-1-oxyl above the Néel temperature using all-electrical propagating
spin-wave spectroscopy in external
magnetic fields. We observe coherently excited low-energy paramagnon-polaritons up to $\mathbf{23\,\mathrm{GHz}}$ , propagating over $\mathbf{8\,\mathrm{mm}}$ at supersonic group velocities exceeding $\mathbf{100\,\mathrm{km\,s^{-1}}}$. Using free radicals as
magnon carriers integrates organic materials with spintronics and opens the way to organic electronics, dense information storage, and
quantum technologies.
Read the full abstract ▾
All authors Sebastian Knauer, Roman Verba, Rostyslav O. Serha, Denys Slobodianiuk, David Schmoll, Andreas Ney, Sergej Demokritov, Andrii Chumak
Materials Science
Probing the Liquid Solid Interfaces of 2D SnSe MXene Battery Anodes at the Nanoscale
Lukas Worch, Kavin Arunasalam, Neil Mulcahy et al. (+5 more)
Understanding degradation processes in lithium ion batteries is essential for improving long term performance and advancing sustainable energy technologies. Tin selenide (SnSe) has emerged as a promising anode material due to the high theoretical capacity of tin. Unlike conventional intercalation based electrodes, SnSe undergoes conversion and alloying reactions with lithium to form Li4.4Sn, Sn, and Li2Se, enabling high lithium storage but inducing large volume changes that cause mechanical instability and capacity fading.
Embedding SnSe nanoparticles within a Ti3C2Tx MXene framework offers a strategy to mitigate these effects by enhancing conductivity and structural resilience. Here, cryogenic focused ion beam (cryo FIB) slice and view revealed progressive material redistribution and morphological transformation during cycling, underscoring the need for site specific chemical analysis. Cryogenic atom probe
tomography (cryo APT) of selected regions provided high spatial and chemical resolution while preserving beam sensitive phases, uncovering nanoscale degradation mechanisms including phase transformations, partial dissolution of active material, and, importantly, the first direct evidence of copper corrosion and copper ion migration from the current collector into the electrode. The observation of copper redistribution demonstrates that current collector degradation contributes directly to chemical contamination and capacity fading in composite electrodes. Together, cryo FIB and cryo APT provide a powerful workflow for elucidating electrode degradation in reactive, beam sensitive systems, offering critical insights for designing more durable and stable next generation battery materials.
Read the full abstract ▾
All authors Lukas Worch, Kavin Arunasalam, Neil Mulcahy, Syeda Ramin Jannat, James Douglas, Baptiste Gault, Valeria Nicolosi, Michele Shelly Conroy
Materials Science
Effect of Concentration Fluctuations on Material Properties of Disordered Alloys
Han-Pu Liang, Chuan-Nan Li, Xin-Ru Tang et al. (+4 more)
Alloying compound AX with another compound BX is widely used to tune material properties. For disordered
alloys, due to the lack of periodicity, it has been challenging to calculate and study their material properties. Special quasi-random structure (SQS) method has been developed and widely used to treat this issue by matching averaged atomic correlation functions to those of ideal random
alloys, enabling accurate predictions of macroscopic material properties such as total energy and volume. However, in AxB1-x
alloys, statistically allowed local concentration fluctuations can give rise to defect-like minority configurations, such as bulk-like AX or BX regions in the extreme, which could strongly affect calculation of some of the material properties such as
semiconductor bandgap, if it is not defined properly, leading to significant discrepancies between theory and experiment. In this work, taking the bandgap as an example, we demonstrate that the calculated
alloy bandgap can be significantly underestimated in standard SQS calculations when the SQS
cell size is increased to improve the structural model and the bandgap is defined conventionally as the energy difference between the lowest unoccupied state and the highest occupied state, because the rare event motifs can lead to wavefunction localization and become the dominant factor in determining the "bandgap", contrary to experiment. To be consistent with experiment, we show that the bandgap of the
alloy should be extracted from the majority configurations using a density-of-states fitting (DOSF) method. This DOSF approach resolves the long-standing issue of calculating electronic structure of disordered
semiconductor alloys. Similar approaches should also be developed to treat material properties that depends on localized
alloy wavefunctions.
Read the full abstract ▾
All authors Han-Pu Liang, Chuan-Nan Li, Xin-Ru Tang, Xun Xu, Chen Qiu, Qiu-Shi Huang, Su-Huai Wei
Materials Science
Direct Raman observation of the quantum metric in a quantum magnet
Chao-Fan Wang, Han Ge, Jun-Yang Chen et al. (+4 more)
The
quantum geometric tensor (QGT) unifies the Berry
curvature (its imaginary part) and the
quantum metric (its real part), yet Raman studies of
chiral phonons have so far accessed only the former. We perform circularly polarized Raman spectroscopy on the
quantum magnet K2Co(SeO3)2, where the field-odd
chiral splitting and the field-even center-frequency shift collapse onto a single curve across temperature and
magnetic field, revealing a common microscopic origin for both observables. Since the
chiral splitting reflects the Berry
curvature, the concomitant even component, arising from the same microscopic origin, captures the field-induced change of the
quantum metric, corresponding to the diagonal Born-Oppenheimer correction. Across two resolvable Eg modes, the unified data are well captured by a simple empirical quadratic relation. These results establish Raman spectroscopy as a direct probe of the
quantum metric and an operational decomposition of
quantum geometry within a single measurement.
Read the full abstract ▾
All authors Chao-Fan Wang, Han Ge, Jun-Yang Chen, Liusuo Wu, Xiaobin Chen, Jia-Wei Mei, Mingyuan Huang