Materials Science · Cross-listed from stat.CO
The generalised balanced power diagram: flat sections, affine transformations and an improved rendering algorithm
Felix Ballani
The generalised balanced power diagram (GBPD) is regarded in the literature as a suitable
geometric model for describing polycrystalline microstructures with curved grain boundaries. This article compiles properties of GBPDs with regard to affine transformations and flat sections. Furthermore, it extends an
algorithm known for power diagrams for generating digital images, which is more efficient than the usual brute force approach, on GBPDs.
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Materials Science · Cross-listed from math.OC
Global Optimization of Atomic Clusters via Physically-Constrained Tensor Train Decomposition
Konstantin Sozykin, Nikita Rybin, Andrei Chertkov et al. (+5 more)
The global optimization of atomic clusters represents a fundamental challenge in computational chemistry and materials science due to the exponential growth of local minima with system size (i.e., the curse of dimensionality). We introduce a novel framework that overcomes this limitation by exploiting the low-rank structure of potential energy surfaces through Tensor Train (TT) decomposition. Our approach combines two complementary TT-based strategies: the algebraic TTOpt method, which utilizes maximum volume sampling, and the probabilistic PROTES method, which employs generative sampling. A key innovation is the development of physically-constrained encoding schemes that incorporate molecular constraints directly into the discretization process. We demonstrate the efficacy of our method by identifying global minima of Lennard-Jones clusters containing up to 45 atoms. Furthermore, we establish its practical applicability to real-world systems by optimizing 20-atom carbon clusters using a machine-learned Moment Tensor Potential, achieving geometries consistent with
quantum-accurate simulations. This work establishes TT-decomposition as a powerful tool for molecular structure prediction and provides a general framework adaptable to a wide range of high-dimensional optimization problems in computational material science.
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All authors Konstantin Sozykin, Nikita Rybin, Andrei Chertkov, Anh-Huy Phan, Ivan Oseledets, Alexander Shapeev, Ivan Novikov, Gleb Ryzhakov
Mesoscale and Nanoscale Physics
Boundary condition for phonon distribution functions at a smooth crystal interface and interfacial angular momentum transfer
Yuta Suzuki, Shuntaro Sumita and Yusuke Kato
We theoretically elucidate the boundary conditions for
phonon distribution functions of long-wavelength acoustic
phonons at smooth
crystal interfaces. We first derive boundary conditions that fully incorporate reflection, transmission, and mode conversion. We obtain these conditions for
phonons from those for classical
lattice vibrations, using the correspondence between the
quantum and classical descriptions. This formulation provides a theoretical foundation for the acoustic mismatch model, widely used to analyze Kapitza resistance. We then refine the boundary conditions to include spatial dependence parallel to the interface. The refined form captures transverse shifts of elastic wave packets, analogous to the optical Imbert–Fedorov shift, and ensures conservation of total angular momentum. Consequently, circularly polarized
phonons carrying
spin angular momentum (SAM) generate
phonon orbital angular momentum (OAM) at the interface. We analytically determine the spatial profile of this OAM and demonstrate that SAM and OAM are both involved in the interfacial
diffusion of
chiral phonons. Our theory provides concise boundary conditions for
phonons, with applications ranging from heat transport to
phonon angular momentum transport.
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Quantum Gases
Supersolid phases and collective excitations in two-dimensional Rashba spin-orbit coupled spin-1 condensates
Sanu Kumar Gangwar, Sayan Chatterjee, Rajamanickam Ravisankar et al. (+3 more)
We investigate the collective excitation spectrum and dynamics of a quasi two-dimensional
spin-1 Bose-Einstein condensate with Rashba type
spin-orbit (SO) coupling. Employing Bogoliubov-de-Gennes analysis, we analytically compute the excitation spectra across a wide range of interaction strengths and coupling parameters. By systematically varying the SO and Rabi couplings, we uncover distinct dynamical signatures of
quantum phase transitions, including mode softening, the appearance of roton-like minima, and miscibility-driven instabilities in both
ferromagnetic and
antiferromagnetic interaction regimes. In the
antiferromagnetic case, these instabilities lead to a dynamically unstable supersolid phase characterized by the coexistence of density modulation and global phase coherence. To corroborate the analytical predictions, we numerically solve the coupled Gross-Pitaevskii equations and analyze the dynamical stability of the condensate. Our results provide experimentally accessible signatures for spinor condensates with tunable
spin-orbit coupling and demonstrate the rich interplay between
spin-dependent interactions and synthetic couplings in nonequilibrium
quantum fluids.
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All authors Sanu Kumar Gangwar, Sayan Chatterjee, Rajamanickam Ravisankar, Henrique Fabrelli, Paulsamy Muruganandam, Pankaj Kumar Mishra
Statistical Mechanics · Cross-listed from math-ph
Finite-Time Transition to Intermittency for a Stochastic Heat Equation Driven by the Square of a Gaussian Field
Philippe Mounaix
In this paper, we study the spatial behavior of the solution $\psi(x,t)$ to the
stochastic heat equation $\partial_t\psi(x,t)-\frac{1}{2}\partial^2_{x^2} \psi(x,t)=g\, S(x,t)^2\, \psi(x,t)$, with $0\le t\le T$, $x\in\mathbb{R}$, and $\psi(x,0)=1$. Here, $g>0$ is a coupling constant and $S(x,t)$ is a stationary, homogeneous, and ergodic Gaussian field. Focusing on $\mathcal{E}(x,g)\equiv \psi(x,T)$ at a finite time $T>0$, we identify the critical coupling $g_c(T)$ above which the average of $\mathcal{E}(0,g)$ diverges. We show that in the subcritical regime $g<g_c(T)$, $\mathcal{E}(x,g)$ is spatially ergodic, with no intermittency, while in the supercritical regime $g>g_c(T)$ it becomes spatially intermittent and loses ergodicity. Our results differ from the extensively studied case where $S(x,t)^2$ is replaced by $S(x,t)$, in which intermittency appears only asymptotically as $T\to +\infty$, with no finite-time intermittency.
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Quantum Gases
Formation Dynamics of Quantum Droplets for Homonuclear and Heteronuclear Mixtures
Enrique Calderoli and Gerardo Martinez
Significant efforts have been devoted to studying the properties of
quantum droplets, an ultra low-temperature phase of bosonic
quantum matter that emerges as a consequence of the Lee-Huang-Yang fluctuating correction. However, the temporal dynamics of droplet formation for heteronuclear bosonic mixtures is only partially understood. Here, we numerically analyze the droplet formation process for homonuclear and heteronuclear binary bosonic mixtures in one dimension, using a tight-binding model and real-time
evolution with a novel, highly robust integration
algorithm. We proceed with a systematic scan of interaction intensities, mass ratios, and initial conditions that allows us to characterize quantitative criteria for droplet formation and
equilibrium prospects. Noticeably, most droplets readily form across the entire parameter space, although only a small fraction achieves a stable
equilibrium configuration within the simulation horizon. We attribute this
equilibrium deficiency to damping from a breathing mode, which we extract directly from the width oscillations at late times. The Lee-Huang-Yang contribution supplies essentially the entire binding energy, while, at late times, the density profile of the equilibrated subset is better described by a
soliton-like shape rather than the flat-topped profiles characteristic of larger droplets. Referring to the energy of the free-atom band, the binding energy grows super-extensively with the number of atoms as $E_{\text{bind}} \propto N^{1.6}$. Heteronuclear droplets bind more strongly as the mass ratio between their components increases and exhibit breathing oscillations that are greater than those of their homonuclear counterparts, which is consistent with the role of mass-imbalanced kinetic terms. Our analysis provides a methodological framework for interpreting real-time
quantum droplet simulations.
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Superconductivity
Exotic vortex states at high magnetic fields in a quasi-two-dimensional FeSe-based superconductor
Xuyang Li, Jian Li, Kai Liu et al. (+9 more)
Owing to strong electronic correlations, high-temperature superconductivity always exhibits intricate intertwinement with various competing electronic orders in phase diagrams, such as
spin/charge density waves (S/CDWs). In cuprate
superconductors,the intertwinement of superconductivity and CDW order could strongly affect the fundamental properties of superconductivity, such as the critical temperature(Tc) and critical
magnetic field(Hc). Recent high-field transport measurements indicate that when
quantum fluctuations become important at low temperatures and high
magnetic fields, the CDW order also reshapes the
vortex states, which leads to fragile superconductivity with extremely low critical current(Jc). Here, by performing comprehensive high-field transport measurements, the H-T phase diagram of
vortex states is mapped to H = 33 T in a quasi-two-dimensional FeSe-based
superconductor (TBA+)xFeSe with a zero-resistivity transition temperature above 40 K. Our results indicate that (TBA+)xFeSe is an extremely type II
superconductor with significant thermal fluctuations.At low temperatures, high
magnetic fields cause the
vortex solid state to exhibit similar current-dependent zero-resistance behavior as the fragile superconductivity in cuprate
superconductors with CDW order. When the
vortex solid state is melted with increasing temperature, a superconducting regime with
vortex-like phase fluctuations emerges as an intermediate state, which features finite longitudinal resistance and vanishing
Hall resistance. At higher temperatures, a
vortex liquid state with finite
Hall resistance eventually appears due to thermal fluctuations. All these observations suggest exotic
vortex states beyond the classical paradigm of
vortex matter.
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All authors Xuyang Li, Jian Li, Kai Liu, Jiaqiang Cai, Shunjiao Li, Baolei Kang, Mengzhu Shi, Dan Zhao, Chuanying Xi, Jinglei Zhang, Tao Wu, Xianhui Chen
Strongly Correlated Electrons
Candidate for a Fractional Topological Insulator in Twisted MoTe2
Yiping Wang, Gillian E. Minarik, Weijie Li et al. (+15 more)
The interplay among electronic correlation,
topology, and time-reversal-
symmetry (TRS) often leads to exotic
quantum states of matter, as highlighted by the discoveries of fractional Chern
insulators (FCIs) in twisted
bilayer MoTe2 (tMoTe2). Among the FCIs in tMoTe2, the most robust is at a hole filling factor of v=-2/3 per moiré unit
cell. Here, employing pump-probe circular dichroism (CD) measurement on tMoTe2 at twist angles (3.9 and 3.7 degrees), we show that a correlated state at v =-4/3 exhibits an unusual Ising antiferromagnet behavior. The v =-4/3 state with no net magnetization undergoes first order phase transitions at extremely low
magnetic fields of ~ 2-6 mT to partially valley polarized (PVP) states. This behavior is notably absent for all other correlated states in tMoTe2 and also disappears for v =-4/3 at higher or lower twist angles (4.0 or 3.3 degree). The observed
magnetic signature is consistent with a theoretically proposed fractional topological
insulator (FTI), consisting of two copies of v =-2/3 FCIs with opposite chirality in the two K valleys. The experimental results are supported by interacting continuum model calculations that reveal the extreme closeness in energy ( < 1 meV) between the putative FTI and PVP states. Our findings present a candidate FTI with TRS and call for advanced transport and imaging measurements to establish the quantized helical edge modes.
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All authors Yiping Wang, Gillian E. Minarik, Weijie Li, Yves Kwan, Shuai Yuan, Eric Anderson, Chaowei Hu, Julian Ingham, Jeongheon Choe, Takashi Taniguchi, Kenji Watanabe, Xavier Roy, Jiun-Haw Chu, Raquel Queiroz, James C. Hone, N. Regnault, Xiaodong Xu, Xiaoyang Zhu
Mesoscale and Nanoscale Physics
Electrostatic Screening Modulation of Graphene's Electronic Structure and the Helical Wavefunction Dominated Topological Properties
Yaorui Tan, Xiang Chen, Yunhu Zhu et al. (+4 more)
This study examines electrostatic screening effects in
graphene using tight binding calculations based on the Binding energy and Bond Charge model and a modified version of it. The results indicate that the modified BBC potential decays in an exponential manner with distance, which suppresses electron electron interactions. The hopping integrals exhibit a pronounced decrease over distance and shift with parameter variation. A band gap opens once the parameter exceeds a certain threshold. The density of states shows a prominent peak near the
Fermi level, whereas the low-energy region remains largely unchanged. The low energy helical wave functions in
graphene display topological characteristics, including pseudospin momentum locking and a {\pi} Berry phase, resulting in distinctive transport properties. By avoiding the Coulomb singularity, the model offers valuable insights for the engineering of screening in two-dimensional systems and the design of topological devices.
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All authors Yaorui Tan, Xiang Chen, Yunhu Zhu, Xiaowu Yang, Zhongkai Huang, Chuang Yao, Maolin Bo
Superconductivity
Superconductivity under pressure in the two-dimensional van der Waals heavy-fermion metal CeSiI
Tong Shi, Wenhao Li, Qingxin Dong et al. (+10 more)
CeSiI is a newly discovered exfoliable van der Waals (vdW) heavy-
fermion metal featured by a long-range
antiferromagnetic (AF) order (TN =7.5 K) inside the Kondo coherent state below T* = 50 K. To gain a more profound understanding of the intriguing physics of this material and to uncover novel phenomena driven by
quantum criticality, it is imperative to construct the phase diagram of CeSiI detailing the evolutions of T* and TN as a function of external tuning parameters such as pressure (P).In this study, we employ high pressure as an effective tuning knob to investigate this system, thereby generating a comprehensive T-P phase diagram of CeSiI. This diagram is characterized by an unusual V-shaped nonmonotonic
evolution of T*(P) and the emergence of a superconducting dome with Tcmax = 240 mK upon suppression of AF order at Pc = 6 GPa, coinciding with the minimum of T*(P).The close proximity of the superconductivity (SC) to the AF instability and an unusually large upper critical field Bc2(0) exceeding 4-7 times the Pauli paramagnetic limit, suggests an unconventional pairing mechanism in CeSiI. Further analyses of normal-state transport properties provide evidence of
quantum criticality, i.e., non-
Fermi-
liquid behavior and divergence of quasiparticle effective mass near Pc = 7 GPa. Our findings not only establish CeSiI as the first vdW heavy-
fermion superconductor but also highlight an unconventional nature for the Kondo coherent state at T* at ambient pressure, hence opening a new avenue to study the interplay of strong electron correlation, Kondo hybridization, magnetism, and unconventional SC in the vdW heavy-
fermion systems.
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All authors Tong Shi, Wenhao Li, Qingxin Dong, Pengtao Yang, Hanming Ma, Zhaoming Tian, Ningning Wang, Jianping Sun, Yoshiya Uwatoko, Yi-feng Yang, Bosen Wang, Hechang Lei, Jinguang Cheng
Superconductivity
Plasmon assisted superconductivity in LiTi$_2$O$_4$
Francesco Petocchi, Viktor Christiansson, Ryotaro Arita et al. (+1 more)
We combine $GW$ plus extended dynamical mean field theory ($GW$+EDMFT) with the density functional theory for
superconductors (SCDFT) framework to study the electronic properties of LiTi$_2$O$_4$. Excellent agreement with experiment is obtained for the density of states, mass enhancement, Sommerfeld coefficient and superconducting $T_c$, if the dynamical nature of the screened Coulomb interaction is taken into account. Our results show that the coupling to collective charge fluctuations (plasmons) plays an important role in the pairing mechanism and explains the remarkably high $T_c$ of this moderately correlated spinel compound.
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All authors Francesco Petocchi, Viktor Christiansson, Ryotaro Arita, Philipp Werner
Materials Science
First-principles study of bulk stacking, $J_{\rm eff}$ picture, magnetic Hamiltonian, $g$ factors, and structural distortions of $\alpha$-RuCl$_3$
Seung-Ju Hong, Tae Yun Kim and Cheol-Hwan Park
$\alpha$-RuCl$_3$ is a candidate Kitaev material that exhibits zigzag
antiferromagnetic ordering below 7 K. One contentious issue regarding this material is its bulk structure in the low-temperature phase. Recently, it has become generally accepted from experiments that the low- and high-temperature structures belong to the $R\bar{3}$ and $C2/m$ space groups, respectively. However, there was no theoretical study supporting the $R\bar{3}$-type structure as the low-temperature structure. In this study, we use constrained density functional theory to show that the $R\bar{3}$ structure is lower in energy than the $C2/m$ structure, in agreement with experimental observations. Then, we show that the conduction band minimum states are almost of the $J_\textrm{eff}=1/2$ and $m_\textrm{eff}=-1/2$ character, if we set the angular momentum quantization axis to be parallel to the Néel vector; this is the first analysis of the $J_\textrm{eff}$ picture for $\alpha$-RuCl$_3$ from this perspective. In addition, we compute the anisotropic
magnetic exchange parameters and $g$ factors of monolayer $\alpha$-RuCl$_3$, thereby providing a comprehensive understanding of its magnetism. Our results demonstrate that both second-nearest-neighbor exchange interactions and
magnetic moments not captured by the conventional atomic orbital projection method are necessary for accurate description of the magnetism in $\alpha$-RuCl$_3$. Moreover, the calculated $g$ factors are in fairly good agreement with experimental measurements, especially the small anisotropy between their in-plane and out-of-plane components. Finally, we examine the effects of structural distortions from a perfect RuCl$_6$ octahedron, already present in bulk $\alpha$-RuCl$_3$ without any external perturbation, on the
magnetic properties. (The abstract is cut here due to the word limit; see the pdf file for the full abstract.)
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Materials Science · Cross-listed from physics.flu-dyn
Spontaneous epicuticular charging affects droplet dynamics on living leaves
Mihir Durve, Serena Armiento, Benham Kamare et al. (+3 more)
How water droplets move and slide on leaves influences plant ecophysiological and abiotic interactions, as well as the design of advanced bio-inspired wetting materials. Despite cross-disciplinary relevance, current descriptions of the in situ dynamics of droplets on living leaves focus almost exclusively on surface structure and chemistry, treating the leaf as a static, electrically neutral substrate. Here, three decades after the mechanistic discovery of the Lotus effect, we show that a yet 'hidden' force due to instantaneous electrical phenomena affect the dynamic droplet motion on living leaves. Using high-speed motion tracking and precision charge measurements, we show that droplets sliding on the pristine epicuticular wax layer on superhydrophobic Colocasia esculenta leaves strongly charge affecting its dynamics, previously observed only on synthetic (highly electronegative fluorinated) surfaces. Droplets accumulate charges of Qp,D1 = -0.02 to -0.15 nC per 30 uL droplet on pristine leaves. However, we specifically demonstrate the crucial role of the epicuticular wax layer plasticity: by a structural modification that decreases its roughness amplitude, the same leaves gain an impressive 30-40 fold enhancement in charge transfer (reaching Qt,D1 = -2.8 to -5.2 nC) slowing the droplet by half due to an estimated electrostatic force of 11 uN dominating the resistive forces. The charge accumulation is surface-history-dependent and charge quantities per droplet are surprisingly similar or even exceeding those recently reported from artificial surfaces. Our findings prove that electrostatic charging is a fundamental component of droplet-leaf interactions, opening new research directions from charge-affected leaf ecology to sustainable materials for droplet-based energy harvesting by tuning surface treatments and, moreover,...
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All authors Mihir Durve, Serena Armiento, Benham Kamare, Sauro Succi, Barbara Mazzolai, Fabian Meder
Statistical Mechanics
Measurement induced faster symmetry restoration in quantum trajectories
Katha Ganguly and Bijay Kumar Agarwalla
Continuous measurement of
quantum systems provides a standard route to
quantum trajectories through the successive acquisition of information which further results in measurement back-action. In this work, we harness this back-action as a resource for global $U(1)$
symmetry restoration where continuous measurement is combined with a $U(1)$-preserving
unitary evolution. Starting from a $U(1)$
symmetry-broken initial state, we simulate
quantum trajectories generated by continuous measurements of both global and local observables. We show that under global monitoring, states containing superpositions of distant charge sectors restore
symmetry faster than those involving nearby sectors. We establish the universality of this behavior across different measurement protocols. Finally, we demonstrate that local monitoring can further accelerate
symmetry restoration for certain states that relax slowly under global monitoring.
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Materials Science
NuMagSANS: a GPU-accelerated open-source software package for the generic computation of nuclear and magnetic small-angle neutron scattering observables of complex systems
Michael P. Adams and Andreas Michels
We present NuMagSANS, a GPU-accelerated software package for calculating
nuclear and
magnetic small-angle
neutron scattering (SANS) cross sections and correlation functions. The program allows users to import position-dependent
nuclear density and magnetization data, providing a large flexibility for analyzing the scattering signatures of complex systems, particularly
magnetic materials. Full rotational control of the sample is supported, allowing a comprehensive exploration of angular-dependent scattering features. NuMagSANS includes a versatile library of approximately 100 response functions that encompass two-dimensional SANS cross sections, correlation functions, and azimuthally averaged quantities. These capabilities allow users to gain detailed insight into the structural and
magnetic characteristics of their samples. GPU acceleration ensures rapid computations, even for large data sets, making NuMagSANS a powerful and efficient tool for advanced SANS analysis.
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Soft Condensed Matter
Self-assembly of quasicrystals under cyclic shear
Raphaël Maire, Andrea Plati, Frank Smallenburg et al. (+1 more)
We investigate the self-assembly of two-dimensional dodecagonal quasicrystals driven by cyclic shear, effectively replacing thermal fluctuations with plastic rearrangements. Using particles interacting via a smoothed square-shoulder potential, we demonstrate that cyclic shearing drives initially random configurations into ordered quasicrystalline states. The resulting non-
equilibrium phase diagram qualitatively mirrors that of thermal
equilibrium, exhibiting square, quasicrystalline, and hexagonal phases, as well as phase coexistence. Remarkably, the shear-stabilised quasicrystal appears even where the zero-temperature
equilibrium ground state favours square-hexagonal coexistence, suggesting that mechanical driving can stabilise quasicrystalline order in a way analogous to entropic effects in thermal systems. The structural quality of the self-assembled state is maximised near the yielding transition, even though the dynamics are slowest there. Yet, the system still quickly forms monodomain quasicrystals without any complex annealing protocols, unlike at
equilibrium, where thermal annealing would be required. Finite-size scaling analysis reveals that global orientational order decays slowly with system size, indicative of quasi-long-range order comparable to
equilibrium hexatic phases. Overall, our results establish cyclic shear as an efficient pathway for the self-assembly of complex structures.
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All authors Raphaël Maire, Andrea Plati, Frank Smallenburg, Giuseppe Foffi
Mesoscale and Nanoscale Physics
Potential of Graphene/AlGaN/GaN heterostructures to study the drag and two-stream instability effects
A. Rehman, D.B. But, P. Sai et al. (+6 more)
Graphene/AlGaN/GaN
heterostructures are proposed to investigate the drag and two-stream instability effects. In this study,
graphene grown by chemical vapor deposition was transferred from copper onto the top of the standard AlGaN/GaN wafer, forming a
heterostructure with two conducting layers separated by an AlGaN barrier layer. Contacts fabricated to the two-dimensional electron gas and
graphene allowed us to study the drag current induced in
graphene by passing the drive current through the two-dimensional electron gas. At low temperatures, the
graphene drag current exhibited
quantum oscillations as a function of the drive voltage. As temperature increases,
quantum oscillations disappear, and the magnitude of the drag current increases.
Graphene/AlGaN/GaN
heterostructures are a promising platform for studying drag and two-stream instability effects, especially if the AlGaN barrier layer thickness can be reduced to a few nanometers.
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All authors A. Rehman, D.B. But, P. Sai, M. Dub, P. Prystawko, A. Krajewska, G. Cywinski, W. Knap, S. Rumyantsev
Strongly Correlated Electrons
Junmo Jeon and Shiro Sakai
Extending hyperuniformity from classical to
quantum fluctuations in electron systems yields a framework that identifies
quantum phase transitions and reveals underlying gap structures through the
quantum weight. We study long-wavelength fluctuations of many-body ground states through the charge-density structure factor by incorporating intrinsic
quantum fluctuations into hyperuniformity. Although charge fluctuations at zero temperature are generally suppressed by particle-number conservation, their long-wavelength scaling reveals distinct universal behaviors that define
quantum hyperuniformity classes. By exemplifying the Aubry-Andre model, we find that gapped, gapless, and localized-critical-extended phases are sharply distinguished by the
quantum hyperuniformity classes. Notably, at the critical point, multifractal wave functions generate anomalous scaling behavior. We further show that, in
quantum-hyperuniform gapped phases, the
quantum weight provides a quantitative measure of the gap size through a universal power-law scaling. Along with classical hyperuniformity,
quantum hyperuniformity serves a direct fingerprint of
quantum criticality and a practical probe of
quantum phase transitions in aperiodic electron systems.
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Soft Condensed Matter
Structural and dynamic anomalous properties of TIP4P/2005 water at extreme pressures
José Martín-Roca, Alberto Zaragoza, Frédéric Caupin et al. (+1 more)
Water shows numerous thermodynamic, dynamic, and structural anomalies. Recent experiments [Eichler et al. Phys. Rev. Lett. 134, 134101 (2025)], based on measurements of shear and bulk viscosities of
liquid water up to 1.6 GPa, have reported the existence of a minimum in the variation of the structural relaxation time {\tau}{\alpha} with pressure at room temperature. Here we investigate this and related properties with molecular dynamics simulations of the TIP4P/2005 water model, performed at extreme pressures commensurate with the experiments. Specifically, we compute dynamic (self-
diffusion, shear and bulk viscosities, and structural relaxation time) and structural (oxygen-oxygen radial distribution function and structure factor, translational order parameter) properties down to 220 K and up to 2.7 GPa. We find good agreement with the experimental observations, and confirm the existence of a minimum in {\tau}{\alpha} . The microscopic information obtained from the simulations suggests that this anomaly is connected with the sudden reorganization of the hydrogen bond network induced by pressurization.
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All authors José Martín-Roca, Alberto Zaragoza, Frédéric Caupin, Chantal Valeriani
Materials Science
Unusual Dual Flat Bands and two-dimensional Dirac-node Arc State in Kagome Metal Ni3In2S2
Bo Liang, Yichen Liu, Jie Pang et al. (+36 more)
Kagome materials are at the frontier of condensed matter physics. An ideal kagome
lattice features only one geometrically frustrated flat band spanning the entire momentum space and a single Dirac cone at the Brillouin-zone corners. However, for the first time, here we observe unusual flat-band and Dirac physics in the newly discovered "322" kagome material Ni3In2S2 by combining high-resolution synchrotron- and
laser-based angle-resolved photoemission spectroscopy with a micro-focused beam, scanning tunneling microscopy, and first-principles calculations. We resolve two distinct electronic flat-band states located in close proximity to the
Fermi level: a robust Topological Surface Flat Band at ~40 meV below the
Fermi level on the Sulfur-terminated surface, originating from weak topological
insulator states, and a kagome
lattice-derived flat band at ~100 meV binding energy with an ultranarrow bandwidth (~5 meV). Instead of the single Dirac cone, the Indium-terminated surface hosts a rare two-dimensional Dirac-node arc state, where the gapless Dirac nodes extend along an open one-dimensional line crossing the Brillouin-zone boundary, exhibiting sharp linear dispersion, exceptionally high
Fermi velocity, and pronounced circular dichroism. These findings establish Ni3In2S2 as a unique topological kagome metal in which multiple flat-band states of different physical origin coexist with an unusual Dirac-node arc, opening an avenue for discovering flat-band–driven and
topology-enabled
quantum phenomena.
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All authors Bo Liang, Yichen Liu, Jie Pang, Hanbin Deng, Taimin Miao, Wenpei Zhu, Neng Cai, Tiantian Zhang, Jiayu Liu, Zhicheng Jiang, Zhanfeng Liu, Hongen Zhu, Yuliang Li, Tongrui Li, Mingkai Xu, Hao Chen, Xiaolin Ren, Chaohui Yin, Yingjie Shu, Yiwen Chen, Yu-Tian Zhang, Zhengtai Liu, Dawei Shen, Mao Ye, Fengfeng Zhang, Shenjin Zhang, Shengtao Cui, Zhe Sun, Koji Miyamoto, Taichi Okuda, Kenya Shimada, Lihong Yang, Jia-Xin Yin, Lin Zhao, Zuyan Xu, Haijun Zhang, Youguo Shi, X. J. Zhou, Guodong Liu
Materials Science
Effect of ballistic re-solution on the nucleation kinetics of precipitates in diluted binary alloys under irradiation. Part 2: Cr-rich alpha' precipitates in Fe-Cr alloys
M.S. Veshchunov
On the base of a critical analysis of existing models for nucleation of new phase precipitates in metastable binary
alloys, a new kinetic model of homogeneous nucleation and growth of alpha'-phase precipitates in Fe-Cr
alloys was developed within the framework of the Reiss kinetic theory of binary nucleation. The model was further modified to account for the influence of ballistic re-solution on the kinetics of nucleation and growth of alpha' precipitates, following the general approach proposed in Part 1. The model was used for qualitative interpretation of the results of recent tests, in which the stability of alpha' precipitates in Fe-15Cr
alloys under irradiation was studied.
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Materials Science
Effect of ballistic re-solution on the nucleation kinetics of precipitates in diluted binary alloys under irradiation. Part 1: Stoichiometric gamma' precipitates in Ni-Al alloys
M.S. Veshchunov
A modification of classical nucleation theory is carried out as applied to solid solutions under irradiation, taking into account the influence of ballistic re-solution on the nucleation kinetics of pure unary (single-component) and stoichiometric binary precipitates. The effects of excessive point defects formed under steady irradiation conditions and operating alongside the ballistic re-solution mechanism are incorporated into the new model for a consistent description of the nucleation of incoherent and coherent particles. The developed model was applied to interpret the results of Nelson, Hudson and Mazey (NHM) tests, in which the stability of gamma' phase (Ni3Al) precipitates in diluted Ni-Al
alloys under irradiation was studied.
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Soft Condensed Matter
Active topological strings in renewing nematopolar fluids
Alberto Dinelli, Ludovic Dumoulin and Karsten Kruse
Active matter often simultaneously exhibits different kinds of orientational order and, in many cases of biological interest, undergoes continuous material renewal. In renewing nematopolar fluids we find stable topological strings, structures consisting of two nematic point defects connected by a defect line in the polar field. We identify the mechanism underlying string stabilization and unveil how string length is determined. In the presence of active stress, we observe active-string chaos. Our work identifies continuous material renewal as a generic mechanism underlying the stabilization of topological defect structures in systems with mixed order parameters. It could be used for orchestrating living matter during development and other biological processes.
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Other Condensed Matter
Higher-order topological bound states in the continuum in a topoelectrical lattice with long-range coupling
Araceli Gutiérrez-Llorente
Linear electric
circuits composed of inductors and capacitors can serve as analogues of tight-binding models that describe the electronic band structure of materials. This mapping provides a versatile approach for exploring topological phenomena within engineered electrical
lattices. In this work, the two-dimensional Su-Schrieffer-Heeger model is examined through electric
circuit analogues to study the interplay between higher-order
topology, bound states in the continuum, and disorder. Building upon this model, the effect of introducing next-nearest-neighbour interactions that preserve
chiral and spatial
symmetries of the system is analyzed. The results reveal that even without
Hamiltonian separability, corner-localized bound states in the continuum remain protected by
symmetry in the long-range coupled
lattice. This robustness highlights the potential of
circuit-based platforms for probing advanced topological phenomena in a highly controllable setting.
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Mesoscale and Nanoscale Physics
Voltage-controlled topological spin textures in the monolayer limit
Yangliu Wu, Bo Peng, Zhaozhuo Zeng et al. (+10 more)
The physics of phase transitions in low-dimensional systems has long been a subject of significant research interest. Long-range
magnetic order in the strict two-dimensional limit, whose discovery circumvented the Mermin-Wagner
theorem, has rapidly emerged as a research focus. However, the demonstration of a non-trivial topological
spin textures in two-dimensional limit has remained elusive. Here, we demonstrate the out-of-plane electric field breaks inversion
symmetry while simultaneously modulating the electronic band structure, enabling electrically tunable
spin-orbit interaction for creation and manipulation of topological
spin textures in monolayer CrI3. The realization of ideal two-dimensional topological
spin textures may offer not only an experimental testbed for probing the Berezinskii-Kosterlitz-Thouless mechanism, but also potential insights into unresolved
quantum phenomena including superconductivity and superfluidity. Moreover, voltage-controlled
spin-orbit interaction offers a novel pathway to engineer two-dimensional
spin textures with tailored
symmetries and
topologies, while opening avenues for skyrmion-based next-generation information technologies.
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All authors Yangliu Wu, Bo Peng, Zhaozhuo Zeng, Chendi Yang, Haipeng Lu, Peiheng Zhou, Jianliang Xie, Difei Liang, Linbo Zhang, Peng Yan, Haizhong Guo, Renchao Che, Longjiang Deng
Strongly Correlated Electrons
Toward Scalable Normalizing Flows for the Hubbard Model
Janik Kreit, Andrea Bulgarelli, Lena Funcke et al. (+4 more)
Normalizing flows have recently demonstrated the ability to learn the Boltzmann distribution of the Hubbard model, opening new avenues for generative modeling in condensed matter physics. In this work, we investigate the steps required to extend such simulations to larger
lattice sizes and lower temperatures, with a focus on enhancing stability and efficiency. Additionally, we present the scaling behavior of
stochastic normalizing flows and non-
equilibrium Markov chain Monte Carlo methods for this fermionic system.
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All authors Janik Kreit, Andrea Bulgarelli, Lena Funcke, Thomas Luu, Dominic Schuh, Simran Singh, Lorenzo Verzichelli
Superconductivity
Direct observation of vortex liquid droplets in the iron pnictide superconductor CaKAs$_4$Fe$_4$ at $0.5T$_c$
Oscar Bou Marqués, Jose A. Moreno, Pablo García Talavera et al. (+7 more)
Type-II
superconductors under
magnetic fields are in a
quantum coherent non-dissipative state as long as
vortices remain pinned. Dissipation appears when
vortices depin, eventually driven by thermal fluctuations. This can be associated to a melting transition between a
vortex solid and a
vortex liquid. This transition is almost always observed very close to T$_c$ when probed by macroscopic experiments. However, it remains unclear how the
vortex solid responds to thermal fluctuations at the scale of individual
vortices far from the melting transition. Here we use scanning tunneling microscopy (STM) to visualize
vortices in CaKAs$_4$Fe$_4$ (T$_c \approx$ 35 K). We find
vortex liquid droplets-localized regions in space where
vortices strongly fluctuate due to thermal exctiation-at temperatures as low as 0.5\,T$_c$. Our results show that the onset of dissipation at the local scale occurs at temperatures considerably below T$_c$ in type-II
superconductors.
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All authors Oscar Bou Marqués, Jose A. Moreno, Pablo García Talavera, Mingyu Xu, Juan Schmidt, Sergey L. Bud'ko, Paul C. Canfield, Isabel Guillamón, Edwin Herrera, Hermann Suderow
Soft Condensed Matter · Cross-listed from physics.flu-dyn
The global attractor of the Toner-Tu-Swift-Hohenberg equations of active turbulence and its properties
Daniel W. Boutros, Kolluru Venkata Kiran, John D. Gibbon et al. (+1 more)
The Toner-Tu-Swift-Hohenberg (TTSH) equations are one of the basic equations that are used to model turbulent behaviour in active matter, specifically the swarming of bacteria in suspension. They combine features of the incompressible Navier-Stokes, the Toner-Tu and Swift-Hohenberg equations, together with the important properties that they are linearly driven, and that the
Laplacian diffusion is taken to be negative in combination with hyper-dissipation. We prove that the TTSH equations possess a finite-dimensional compact global attractor on the periodic domain $\mathbb{T}^d$ ($d=2,3$) and we establish explicit estimates for its Lyapunov dimension which agree with the heuristic prediction based on the Swift-Hohenberg length scale. The predominance of this length scale (as a
vortex length scale) has been observed in both numerical and experimental studies of bacterial
turbulence, so our methods and results provide a rigorous theoretical foundation for this phenomenon. We also carry out pseudospectral direct numerical simulations of these PDEs in dimension $d=2$ through which we obtain Lyapunov spectra for representative parameter values. We show that our numerical results are consistent with the analytically derived rigorous bounds.
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All authors Daniel W. Boutros, Kolluru Venkata Kiran, John D. Gibbon, Rahul Pandit
Quantum Gases
Breakdown of bosonic Thouless pump due to interaction in a quasiperiodic lattice
Suman Mondal, Emmanuel Gottlob, Fabian Heidrich-Meisner et al. (+1 more)
We investigate the effect of inter-particle interaction on the quantized Thouless pump in the bosonic quasiperiodic Aubry-André model and find that the quantization of the pumped charge breaks down already for weak interactions. Furthermore, the pumped charge undergoes sharp changes as a function of interaction strength that we can attribute to the closing of specific doublon channels. As expected, the quantization revives in the hard-core limit at very large interaction strengths where the
bosons are subject to a hardcore constraint. Interestingly, the stability of isolated doublons under the pump depends on the band they are in. For repulsive interactions and a suitably fixed pump period, doublons in the lowest band are pumped stably while doublons in higher bands dissociate during the pump with one particle decaying into a lower band. This asymmetry leads to the decay of the total energy over time, in stark contrast to the typical Floquet heating expected for a driven many-body system.
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All authors Suman Mondal, Emmanuel Gottlob, Fabian Heidrich-Meisner, Ulrich Schneider
Statistical Mechanics
Separating Energy and Entropy Contributions to the Hexatic-Liquid Transitions in Two-Dimensional Repulsive Systems
Yan-Wei Li, Rui Ding and Wen-Hao Ma
Over the past decades, research on two-dimensional melting has established that both first-order and continuous hexatic-
liquid transitions can occur, influenced by various factors in the potential energy and system details. The fundamental thermodynamic origins of this sensitivity remains elusive. Here, by decomposing the Helmholtz free energy across three representative repulsive systems, we reveal a universal competition between energy and
entropy that dictates the melting pathway. The energetic contribution consistently imparts convexity to the free energy, whereas
entropy imparts concavity. A first-order transition occurs when concave
entropy dominates; otherwise, the transition is continuous. Further decomposition shows that vibrational
entropy drives the concave total entropic
curvature, while the configurational
entropy's
curvature switches from convex (first-order) to concave (continuous), mirroring defect proliferation measured by Shannon
entropy. The convexity of the energy is dominated by the inherent potential, with minimal vibrational influence. Finally, we predict and verify that the first-order transition becomes continuous at zero temperature, where entropic effects vanish. Our work establishes the
curvature of different thermodynamic quantities as a fundamental principle for understanding the nature of two-dimensional melting.
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