Statistical Mechanics
Learning to outgrow the competition: reaction-diffusion systems that adapt to time-dependent environments
Olivier Rivoire and Guy Bunin
A fundamental challenge in both biology and engineering is understanding how adaptation can emerge from simple physical or chemical building blocks. Biological adaptation appears to rely on two key capabilities: information processing, to enable learning of complex tasks, and reproduction, to give such learning its value through reproductive success. Creating and coordinating these capabilities poses both a formidable engineering challenge and a fundamental evolutionary puzzle. Here, we propose a model in which learning and reproduction emerge jointly from simple, nonequilibrium chemical systems, without prior design or
evolution. The model's essential features are that it supports many steady states and spatial heterogeneities, upon which adaptation arises solely from exposure to time-varying influxes of reactants, without any predesigned program or
memory. The adaptive response is specific to the temporal sequence of environmental changes, yet general enough to extend to related sequences. Learning manifests in several forms: it is reinforced through repeated exposure to the same environmental sequence, representing a form of self-learning, and enhanced through spatial interactions, corresponding to a form of collective learning. Moreover, an adapted state can accelerate adaptation in nearby regions, providing a mechanism akin to teacher-guided learning. By coupling environmental variations to
stochastic reaction-
diffusion dynamics, our model establishes a minimal physical framework in which learning of complex environments and selective amplification of the states that encode them, arise directly from nonequilibrium chemical processes.
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Materials Science
Second-Order Jahn-Teller Distortions and Dynamic Lattice Polarizability as the Origin of Broadband Emission in Bi3+-Doped Cs2SnCl6
Shruti Prasad, Pabitra Kumar Nayak and Dibyajyoti Ghosh
Lead-free vacancy-ordered perovskites (VOHPs) such as Cs2SnCl6 have emerged as promising materials for optoelectronic applications but typically suffer from wide band gaps and low photoluminescence
quantum yields (PLQY). In this work, the electronic origins of broadband blue emission in Bi3+-doped Cs2SnCl6 are elucidated by combining density functional theory (DFT) calculations and ab initio molecular dynamics simulations. The study systematically explores the spatial configurations of Bi3+ dopants and Cl-vacancies, assessing their impact on structural and electronic properties. Results demonstrate that the formation of square pyramidal BiCl5(2-) units serves as efficient
exciton traps, fundamentally enabling strong luminescence in an otherwise non-emitting host. The Bi3+ 6s2 lone pair in an asymmetric coordination environment drives second-order Jahn-Teller distortions, creating a highly polarizable local
lattice. This softness, in contrast to the rigid SnCl6(2-) framework, produces heterogeneous distributions of bond lengths, bond angles, and band edges around dopant sites. Defect-induced states strongly localize charge carriers, while coupling to vibrational modes at 300 K dynamically broadens the band edges, accounting for the large Stokes shift and broadband photoluminescence. These results establish lone-pair-driven Jahn-Teller distortions and
lattice heterogeneity as key design principles for efficient luminescence in lead-free perovskites.
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Other Condensed Matter · Cross-listed from math-ph
Exact quantum dynamics of Fermi–Hubbard systems using the Gaussian phase-space representation with diffusion gauges
F Rousse, M Fasi, A Dmytryshyn et al. (+3 more)
We use the Gaussian Phase-Space Representation to solve the real-time dynamic of interacting
fermions in 1D, 2D, and 3D systems. The method is exact up to a spiking point, which represents a limit on the practical simulation time. The spiking can be delayed, and the practical simulation time extended, by adjusting the gauges of the representation, resulting in different equivalent
stochastic differential equations. Here, we work on the so-called
diffusion gauge and propose an
algorithm to find efficiently new implementations of the noise terms. Compared with our initial results [F. Rousse et al. 2024, J. Phys. A: Math. Theor. 57, 015303], the new method achieves a significantly longer practical simulation time and can be applied to significantly larger systems.
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All authors F Rousse, M Fasi, A Dmytryshyn, M Gulliksson, J F Corney, M Ogren
Disordered Systems and Neural Networks · Cross-listed from q-bio.NC
Symmetries at the origin of hierarchical emergence
Fernando E. Rosas
Many systems of interest exhibit nested emergent layers with their own rules and regularities, and our knowledge about them seems naturally organised around these levels. This paper proposes that this type of hierarchical emergence arises as a result of underlying
symmetries. By combining principles from information theory, group theory, and statistical mechanics, one finds that dynamical processes that are equivariant with respect to a
symmetry group give rise to emergent macroscopic levels organised into a hierarchy determined by the subgroups of the
symmetry. The same
symmetries happen to also shape
Bayesian beliefs, yielding hierarchies of abstract belief states that can be updated autonomously at different levels of resolution. These results are illustrated in Hopfield networks and Ehrenfest
diffusion, showing that familiar macroscopic quantities emerge naturally from their
symmetries. Together, these results suggest that
symmetries provide a fundamental mechanism for emergence and support a structural correspondence between objective and epistemic processes, making feasible inferential problems that would otherwise be computationally intractable.
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Strongly Correlated Electrons
Magnetic clusters in the paramagnetic phase of a high-temperature ferromagnetic metal-organic framework
Giacomo Prando, Benjamin Costarella, Matthew S. Dickson et al. (+10 more)
Owing to their exceptional chemical and electronic tunability, metal-organic frameworks can be designed to develop
magnetic ground states making a range of applications feasible, from
magnetic gas separation to the implementation of lightweight, rare-earth free permanent magnets. However, the typically weak exchange interactions mediated by the diamagnetic organic ligands result in ordering temperatures confined to the cryogenic limit. The itinerant
magnetic ground state realized in the chromium-based framework Cr(tri)$_{2}$(CF$_{3}$SO$_{3}$)$_{0.33}$ (Htri, $1H$-$1$,$2$,$3$-triazole) is a remarkable exception to this trend, showing a robust
ferromagnetic behavior almost at ambient conditions. Here, we use dc SQUID magnetometry,
nuclear magnetic resonance, and
ferromagnetic resonance to study the
magnetic state realized in this material. We highlight several thermally-activated relaxation mechanisms for the
nuclear magnetization due to the tendency of electrons towards localization at low temperatures as well as the rotational dynamics of the charge-balancing triflate ions confined within the pores. Most interestingly, we report the development within the paramagnetic regime of mesoscopic
magnetic correlated clusters whose slow dynamics in the MHz range are tracked by the
nuclear moments, in agreement with the highly unconventional nature of the
magnetic transition detected by dc SQUID magnetometry. We discuss the similarity between the clustered phase in the paramagnetic phase and the magnetoelectronic phase segregation leading to colossal magnetoresistance in manganites and cobaltites. These results demonstrate that high-temperature
magnetic metal-organic frameworks can serve as a versatile platform for exploring correlated electron phenomena in low-density, chemically tunable materials.
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All authors Giacomo Prando, Benjamin Costarella, Matthew S. Dickson, Ryan A. Murphy, Jesse G. Park, Gianrico Lamura, Giuseppe Allodi, Cristian Aloisi, Aëto Apaix, Maria Cristina Mozzati, T. David Harris, Jeffrey R. Long, Pietro Carretta
Materials Science
Crystalyse: a multi-tool agent for materials design
Ryan Nduma, Hyunsoo Park and Aron Walsh
We present Crystalyse, an open, provenance-enforced scientific
agent for computational materials design of inorganic
crystals that orchestrates tools for compositional screening,
crystal structure generation, and machine-learning force-field evaluation. Crystalyse offers three operating modes to trade exploration speed against validation depth: creative (rapid query), adaptive (context-aware routing) and rigorous (comprehensive checks). We release the underlying source code and evaluation scripts to enable plug-and-play use and development. In demonstrations on quaternary
oxide exploration, sodium-ion cathode design, and lead-free indoor photovoltaic candidate generation, the
agent integrates chemical compound generation with fast stability and property filters. Under
adversarial testing, provenance enforcement eliminated material-property
hallucinations (a broad
adversarial suite pass rate reached 86% from a 57% baseline). Crystalyse provides an agentic artificial intelligence system that can complement existing materials design pipelines, assisting in hypothesis generation while preserving transparency and reproducibility.
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Materials Science
Observation of hidden altermagnetism in Cs$_{1-\delta}$V$_2$Te$_2$O
Guowei Yang, Ruihan Chen, Changchao Liu et al. (+25 more)
Altermagnets are characterized by anisotropic band/
spin splittings in momentum space, dictated by their
spin-space group
symmetries. However, the real-space modulations of altermagnetism are often neglected and have not been explored experimentally. Here we combine
neutron diffraction, angle-resolved photoemission spectroscopy (ARPES),
spin-resolved ARPES and density functional theory to demonstrate that Cs$_{1-\delta}$V$_2$Te$_2$O realizes a spatially modulated form of altermagnetism, i.e., hidden altermagnetism. Such a state in Cs$_{1-\delta}$V$_2$Te$_2$O results from its G-type antiferromagnetism and two-dimensional electronic states, allowing for the development of spatially alternating altermagnetic layers, whose local
spin polarizations are directly verified by
spin-resolved ARPES measurements. Our experimental discovery of hidden altermagnetism broadens the scope of unconventional magnetism and opens routes to exploring emergent phenomena from real-space modulations of altermagnetic order.
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All authors Guowei Yang, Ruihan Chen, Changchao Liu, Jing Li, Ze Pan, Teng Hua, Pengyue Xiong, Liwei Deng, Naifu Zheng, Yu Tang, Hao Zheng, Weifan Zhu, Yifu Xu, Xinying Zheng, Xin Ma, Xiaoping Wang, Shengtao Cui, Zhe Sun, Zhengtai Liu, Mao Ye, Chao Cao, Ming Shi, Lunhui Hu, Qihang Liu, Shan Qiao, Guanghan Cao, Yu Song, Yang Liu
Statistical Mechanics · Cross-listed from quant-ph
Quantum ramp secret sharing from Haar scrambling
Kiran Adhikari
Quantum information scrambling has emerged as a powerful tool for studying the dynamics of chaotic
quantum many-body systems, assessing benchmarking protocols, and even investigating exotic black hole models. During
quantum information scrambling, localized
quantum information disperses across the entire system, hiding from the observers who can only access part of it. On the other side, we have a fundamental cryptographic primitive called secret-sharing schemes, where a dealer shares a
quantum secret with a group of parties, such that any subset of parties above a specific threshold size can reconstruct it. In this paper, we demonstrate that two protocols, Haar scrambling, which serves as a baseline for other scrambling techniques, and
quantum secret sharing, are indeed equivalent. The scheme one gets out of this is of a ramp secret-sharing nature rather than a threshold scheme. We expect this because of the inherent randomness present in Haar
unitaries. Moreover, by varying the purity of the initial states, we demonstrate that it is possible to obtain all possible types of ramp secret-sharing schemes. Furthermore, utilizing complexity theoretic arguments, we argue that the protocol can be implemented efficiently, i.e., in
polynomial time. Finally, we explore potential applications, ranging from security implications for distributed
quantum networks to cryptography in the Noisy Intermediate-Scale
Quantum (NISQ) era, and draw insights for fundamental physics, such as many-body physics and
quantum black holes.
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Materials Science
Charge state equilibration of nitrogen-vacancy center ensembles in diamond: The role of electron tunneling
Audrius Alkauskas, Chris G. Van de Walle, Lukas Razinkovas et al. (+1 more)
The charge state stability of nitrogen-vacancy (NV) centers critically affects their application as
quantum sensors and
qubits. Understanding charge state conversion and equilibration is critical not only for NV centers in diamond but also for defects and
impurities in wide-bandgap materials in general. The mechanisms by which these centers change charge state upon optical or electronic excitation without the presence of mobile carriers remain unclear, potentially affecting the performance of applications ranging from phosphors to power electronics. Here, we elucidate this issue for the case of photoionization of NV center ensembles. Using pump-probe spectroscopy, we ionize negatively charged NV centers and monitor the recovery of $\NVm$ on timescales of up to several seconds. We find that the recovery rate depends strongly on the concentration of surrounding nitrogen donors. Remarkably, the equilibration dynamics exhibit no discernible dependence on temperature, ruling out thermally activated processes. The multiphonon-assisted electron tunneling model, supported by density-functional calculations, explains the measurements and identifies tunneling as the equilibration mechanism.
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All authors Audrius Alkauskas, Chris G. Van de Walle, Lukas Razinkovas, Ronald Ulbricht
Statistical Mechanics
Canonical Distribution of the Occupancy Numbers of Bosonic Systems
Arnaldo Spalvieri
The paper works out the canonical probability distribution of the occupancy numbers of a bosonic system and shows that canonical typicality applies to the canonical density operator of the occupancy numbers. The result is that, if, as it is today standard, the canonical system's mixed state is obtained by tracing out the environment from any typical pure state of the universe, then asymptotically the canonical probability distribution of system's occupancy numbers tends in probability to the multinomial distribution. The paper also shows that the currently accepted probability distribution of the occupancy numbers of a system with fixed number of particles is not compatible with the commonly accepted notion of canonical system.
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Statistical Mechanics
A mean-field theory of effective normal modes in the Fermi-Pasta-Ulam-Tsingou model
Antonio Ponno, Giacomo Gradenigo, Marco Baldovin et al. (+1 more)
We present a non-perturbative, mean-field theory for the
Fermi-Pasta-Ulam-Tsingou model with quartic interaction, capturing the quasiperiodic features shown by the system at all energies in the thermodynamic limit. Starting from the true
Hamiltonian $H$ of the system with $N$ degrees of freedom, we introduce a mean-field
Hamiltonian $\mathcal{H}$ such that the difference $h_N=(H-\mathcal{H})/N$, considered as a random variable with respect to the Gibbs measure, tends to zero as $N\to\infty$, in probabilistic sense. The dynamics of the mean-field
Hamiltonian $\mathcal{H}$ consists of $N$ independent oscillation modes with renormalized frequencies $\Omega_k = \omega_k\sqrt{1+\gamma(\varepsilon)}$, $\omega_k$ being the frequency of the $k$-th normal mode of the linearized system, whereas $\gamma(\varepsilon)$ is an explicit function of the specific energy $\varepsilon$ of the system. Analytical predictions drawn from the effective Langevin equations ruling the dynamics of such oscillation modes are successfully compared with the numerical data from the original
Hamiltonian dynamics. Such a simple decomposition of the true dynamics into $N$ effective normal modes holds at all energy scales, i.e. from the quasi-integrable regime to the strongly chaotic one.
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All authors Antonio Ponno, Giacomo Gradenigo, Marco Baldovin, Angelo Vulpiani
Materials Science
Exchange-Correlation Functionals in 2D Materials: Applications, Challenges, and Limitations
Ahsan Javed, Mahvish Shaheen, Muhammad Shahbaz et al. (+3 more)
The rapid development of two-dimensional (2D) materials has reshaped modern nanoscience, offering properties that differ fundamentally from their bulk counterparts. As experimental discovery accelerates, the need for reliable computational techniques has become increasingly important. Within the framework of density functional theory, this review explores the critical role of exchange-correlation functionals in predicting key material properties such as structural, optoelectronic,
magnetic, and thermal. We examine the challenges posed by
quantum confinement, anisotropic screening, and van der Waals interactions, which conventional functionals often fail to describe. Advanced approaches, including meta-GGA, hybrid functionals, and many-body perturbation theory (e.g., GW and Bethe-Salpeter equation), are assessed for their improved accuracy in capturing electronic structure and excitonic effects. We further discuss the non-universality of functionals across different 2D material families and the emerging role of machine learning to enhance computational efficiency. Finally, the review outlines current limitations and emerging strategies, providing a roadmap for advancing exchange-correlation functionals and beyond, to enable the practical design and application of 2D materials.
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All authors Ahsan Javed, Mahvish Shaheen, Muhammad Shahbaz, M. Sufyan Ramzan, Rafi Ullah, Wei Jiang
Mesoscale and Nanoscale Physics
Field-Tunable Quantum Metric in Few-Layer Phosphorene
Md Afsar Reja, Arka Bandyopadhyay and Awadhesh Narayan
The
quantum metric – which quantifies the distance between
quantum states – is a fundamental component of the
quantum geometric tensor, playing a crucial role in a wide range of physical phenomena. Its direct detection and control remains a challenge, requiring suitable material candidates. In this work, we present the emergence of a tunable
quantum metric in a versatile two-dimensional material platform, namely, few-layer phosphorene. Using ab-initio-derived models, we show how electric fields can be used to substantially enhance the
quantum metric as well as the associated
quantum weight. Furthermore, we present a layer-dependent
evolution of the
quantum metric and its interplay with the electric field in this material. Our results establish few-layer phosphorene as a promising platform for exploring control over the
quantum metric and the resulting metric responses in real materials.
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Strongly Correlated Electrons
Electric-field driven flat bands in the distorted sawtooth chain via the Katsura-Nagaosa-Balatsky mechanism
Vadim Ohanyan, Lusik Amiraghyan, Michael Sekania et al. (+1 more)
We investigate flat magnonic bands in a generalized sawtooth-chain model in which three sets of exchange parameters (symmetric Heisenberg exchange, axial Ising anisotropy, and antisymmetric Dzyaloshinskii-Moriya (DM) exchange) are assigned independently to each side of the triangular plaquette. If the effective Dzyaloshinskii-Moriya (DM) interaction parameters are generated via the Katsura-Nagaosa-Balatsky (KNB) mechanism of magnetoelectricity, they become explicit functions of the electric-field magnitude and direction, as well as of the
lattice geometry, which in the present casen is characterized by two bond angles. We focus on the situation in which these two angles are unequal, corresponding to a distortion of the triangular plaquette. Several electric-field induced flat-band scenarios in the distorted sawtooth chain are analyzed, and expressions are derived for the electric-field strength required to drive the one-
magnon excitations into a flat-band regime when the field is aligned along the
lattice bonds. The saturation field and its dependence on the distortion angle are also examined. Finally, we establish a mapping between the flat-band solutions for a general DM interaction and its specific KNB-induced form. \\~ This article is dedicated to the
memory of Johannes Richter.
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All authors Vadim Ohanyan, Lusik Amiraghyan, Michael Sekania, Marcus Kollar
Statistical Mechanics · Cross-listed from math-ph
Generalized Boltzmann-Gibbs Distribution and the Electronic Partition Function Paradox
Leandro Lyra Braga Dognini
This paper generalizes the
entropy maximization problem leading to the Boltzmann-Gibbs distribution through the nonadditive
entropy $S_{q,s}(p)=k_{s}\sum^{W}_{i\geq1}p_{i}\ln_{q}1/p_{i}$, $q\in(0,1)$, which is a rescaled version of $S_{q}$ \cite{Tsallis1988} by a factor $k_{s}=k^{q}(e_{\max}/(W^{\sigma}-1))^{1-q}$, $\sigma>0$, varying according to the underlying energy spectrum and satisfying $k_{s}\rightarrow k$ (Boltzmann constant) as $q\rightarrow 1$. The maximization problem based on $S_{q,s}$ is used to derive analytical generalizations of the Boltzmann-Gibbs distribution for the case of an energy spectrum that uniformly approaches a continuous, unbounded limit with a common degeneracy, the harmonic oscillator, and the one-dimensional box. Furthermore, I demonstrate that this generalized problem yields a two-tier model with finite structural parameters $\beta$ for the hydrogen atom in free space and, therefore, can be used to circumvent the Electronic Partition Function Paradox and obtain a family of well-defined thermodynamic behaviors indexed by $q\in(0,1)$. In particular, for $q=0.5$, the specific heat of the free hydrogen atom becomes the Boltzmann constant. Finally, it is shown that all the limiting processes involved in these four cases lead naturally to the same definition of the scale factor $k_{s}$ that characterizes $S_{q,s}$ (“s” stands, in this context, for “spectrum”) in order to grant finite, smooth, macroscopically observable temperature values that are related to the entropic functional by $\partial S_{q,s}/\partial U=1/\vert T\vert^{q}_{\pm}$, which recovers $\partial S_{BG}/\partial U=1/T$ \cite{Clausius1865} as $q\rightarrow1$.
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Mesoscale and Nanoscale Physics
Stacking-Induced Large-Chern-Number Quantum Anomalous Hall Phases
H. Minh Lam and V. Nam Do
We investigate the interaction between
quantum anomalous
Hall (QAH) phases hosted by two atomically thin hexagonal
lattices and demonstrate the emergence of topological phases with large Chern numbers. Interlayer coupling between two
graphene-like
lattices produces band crossings, while relative sliding preserves gapless Dirac points located at generic, low-
symmetry $\mathbf{k}$ points. The introduction of Haldane-type complex next-nearest-neighbor hoppings gaps these Dirac points, breaks time-reversal
symmetry, and generates a sequence of
quantum anomalous
Hall phases. Depending on the phase angles $\phi_1$ and $\phi_2$ associated with the two layers, the system exhibits QAH states with Chern numbers $|C|>2$. The nontrivial bulk
topology is verified by the presence of the corresponding number of
chiral edge modes in ribbon geometries. These high-Chern-number phases originate from the enhanced twisting of the valence-band
manifold induced by interlayer stacking.
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Mesoscale and Nanoscale Physics
Screened topological plasmons in graphene plasmonic crystals
André Octávio Soares, Christos Tserkezis and N. M. R. Peres
We study topological effects in an one-dimensional plasmonic
crystal formed by the screened plasmons emerging in a periodically modulated
graphene sheet, placed on top of a metallic substrate. To this end, we develop the theory of quantization of screened plasmons, as appropriate for lossless
graphene described by a Drude conductivity. By analyzing the resulting band structure, we show that the
crystal sustains nontrivial topological bands, with quantized
geometric phase. We further show that in a finite, open system, edge states appear within the band gap, which undergo a topological phase transition and merge with bulk states as the modulation increases. Our work provides a robust theoretical framework for the study of band structure and
topology of layered media, and extends the possibilities for engineering two-dimensional materials with external modulation.
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Quantum Gases
Spectral form factor and power spectrum for trapped interacting rotating bosons: Crossover from integrability to quantum chaos
Mohd Talib and M. A. H. Ahsan
The emergence of
quantum chaos in a system of trapped interacting
bosons with externally impressed rotation is studied through spectral form factor (SFF) and power spectrum using exact diagonalization. Two distinct interaction regimes are considered: the moderate, when the interaction energy is small compared to the trap energy and the strong, when the interaction energy is comparable to the trap energy. In the moderate interaction regime, the SFF for the non-rotating case exhibits a dip-plateau structure with absence of linear ramp, indicating integrable behavior, while for the single-
vortex state the SFF exhibits a discernible linear ramp consistent with pseudo-integrable behavior. In the strong interaction regime, the non-rotating case exhibits emergence of a linear ramp with small time span in SFF, indicating that the system has moved further towards chaotic regime but continues to be pseudo-integrable. For the single-
vortex and the multi-
vortex states in strong interaction regime, the span of the linear ramp in SFF increases progressively with rotation, indicating the system has moved into strong chaotic regime consistent with Gaussian orthogonal ensemble. The power spectrum results with exponent lying in the interval $1 \lesssim \alpha \lesssim 2$ are consistent with the findings of SFF. An understanding of the observed crossover from integrable to
quantum chaos is presented in terms of the macroscopic occupation of a single-particle
quantum state—the Bose-Einstein condensation—and its depletion driven by interaction and rotation.
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Mesoscale and Nanoscale Physics
Helical Edge Transport in the \nu = 0 Quantum Hall Ferromagnetic State of an Organic Dirac Fermion System
Toshihito Osada, Mitsuyuki Sato, Takako Konoike et al. (+1 more)
We experimentally confirm the \nu = 0
quantum Hall ferromagnetic (QHF) state, accompanied by helical edge states, in the layered organic Dirac-
fermion system \alpha-(ET)2I3 by demonstrating helical edge transport in multilayers. The saturation of interlayer magnetoresistance (MR) in the high-
magnetic-field
quantum limit does not scale with the sample cross-sectional area and appears when the
magnetic field is oriented along the side surface. The in-plane MR exhibits a similar angle dependence, whereas this feature disappears in the Corbino geometry where no edge channels are present. These results are consistent with helical edge transport in the multilayer QHF state. They also rule out the possibility that the observed angle-dependent MR arises from the
chiral magnetic effect expected for a 3D Dirac or Weyl semimetal.
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All authors Toshihito Osada, Mitsuyuki Sato, Takako Konoike, Woun Kang
Materials Science
Yeongju Choi, Seungjin Lee, Dongwon Shin et al. (+12 more)
Hybrid
heterostructures composed of
graphene and perovskite
oxides provide a promising platform for exploiting synergetic interfacial functionalities. Conventional fabrication methods of the hybrid
heterostructures rely on transferring
graphene grown on metallic substrates– a process that is time-consuming, labor-intensive, and prone to introducing numerous defects. In this study, we present a universal, catalyst-free method for the direct growth of
graphene on insulating substrates by employing three different perovskite
oxide substrates (SrTiO$_3$, LaAlO$_3$, and (La$_{0.18}$Sr$_{0.82}$)(Al$_{0.59}$Ta$_{0.41}$)O$_3$) using atmospheric chemical vapor deposition. Comprehensive characterization via Raman spectroscopy, X-ray spectroscopy, scanning probe microscopy, and electron microscopy confirmed the formation of a uniform, continuous monolayer
graphene on all substrates. We identified that growth temperature critically governs
graphene quality, as excessive active species may lead to secondary nucleation and the formation of multilayer
graphene. Notably, all substrates shared the same optimal growth conditions. Low-temperature Raman spectroscopy and scanning tunneling microscopy of the
graphene/SrTiO$_3$ hybrid
heterostructure revealed cooperative phenomena, including substrate-induced
lattice-
phonon and electron-
phonon coupling. Our work establishes a reproducible, transfer-free fabrication route for
graphene/perovskite
oxide hybrid
heterostructures and provides empirical support for the universal growth of
graphene on insulating substrates.
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All authors Yeongju Choi, Seungjin Lee, Dongwon Shin, Sukhoon Sim, Min-Hyoung Jung, Dirk Wulferding, Minjae Kim, Jaesik Eom, Myeesha Mostafa, Wonhee Ko, SeungNam Cha, Jungseek Hwang, Hu Young Jeong, Ki Kang Kim, Woo Seok Choi
Statistical Mechanics · Cross-listed from math-ph
Braided quantum mechanics and Majorana qubits at third root of unity: a color Heisenberg-Lie (super)algebra framework
Zhanna Kuznetsova and Francesco Toppan
We introduce color Heisenberg-Lie (super)
algebras graded by the abelian groups $Z_3^2$, $Z_2^p\times Z_3^2$ for $p=1,2,3$, and investigate the properties of their associated multi-particle
quantum paraoscillators. In the Rittenberg-Wyler's color Lie (super)
algebras framework the above abelian groups are the simplest ones which induce mixed brackets interpolating commutators and anticommutators. These mixed brackets allow to accommodate two types of parastatistics: one based on the permutation group (beyond
bosons and
fermions in any space dimension) and an anyonic parastatistics based on the braid group. In both such cases the two broad classes of paraparticles are given by parabosons and parafermions. Mixed-bracket parafermions are created by nilpotent operators; they satisfy a generalized Pauli exclusion principle leading to roots-of-unity truncations in their multi-particle energy spectrum (braided Majorana
qubits and their Gentile-type parastatistics are recovered in this color Lie superalgebra setting). Mixed-bracket parabosons do not admit truncations of the spectrum; the minimal detectable signature of their parastatistics is encoded in the measurable probability density of two indistinguishable parabosonic oscillators in a given energy eigenstate.
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Quantum Gases
Shawan K. Jha, Makoto Tsubota and Pankaj K. Mishra
In this work, we analyze the
evolution of four
vortex configurations, namely, dipole,
plasma, cluster, and
lattice, using the two-dimensional mean-field Gross-Pitaevskii equation, focusing on their dynamical decay and approach to the
equilibrium. Our analysis reveals that the cluster
vortex configuration reaches
equilibrium more rapidly than the others, while the dipole,
plasma, and
lattice configurations exhibit persistent non-
equilibrium behavior, tending toward non-thermal fixed points. Specifically, the cluster configuration follows Kolmogorov-like scaling ($\varepsilon^{i}(k)\sim k^{-5/3}$) in the incompressible spectrum, while the other configurations follow Vinen-like scaling ($\varepsilon^{i}(k)\sim k^{-1}$). In the compressible spectrum, the cluster case exhibits a $k$ scaling, indicating full mode equilibration, while for the other configurations, the modes thermalize only above a critical wave number. Additionally, the transfer function for the cluster configuration displays a Gaussian distribution, typical of
equilibrium states, while the other configurations exhibit skewed Gaussian or exponential distributions, indicative of their non-
equilibrium nature. Finally, the particle number spectra show that the cluster case follows dynamical scaling closer to
equilibrium, while the dipole,
plasma, and
lattice configurations evolve towards non-thermal fixed points. Our findings provide new insights into the dynamics of
vortex configurations and their approach to
equilibrium or non-
equilibrium states, offering guidance for future studies on
quantum turbulence and its control.
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Superconductivity
Observation of individual vortex penetration in a coplanar superconducting resonator
Kirill Shulga, Shunsuke Nishimura, Pavel A. Volkov et al. (+7 more)
We demonstrate the microwave signatures of individual Abrikosov-
vortex penetration events in superconducting microwave resonators. $\lambda/4$ resonators with a narrowed region near the grounded end acting as a
vortex trap were fabricated and studied using microwave transmission spectroscopy at millikelvin temperatures. Sharp stepwise drops in resonance frequency are detected as a function of increasing external
magnetic field, attributed to the entry of individual Abrikosov
vortices in the narrow region. This interpretation is confirmed by NV center magnetometry revealing discrete
vortex entry events on increasing field and the absence of such drops in a device with a wider narrowed region. Our results establish a method to investigate and manipulate the states of Abrikosov
vortices with microwaves access and readout
vortex configurations using
magnetic-field sweeps and microwave drive.
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All authors Kirill Shulga, Shunsuke Nishimura, Pavel A. Volkov, Ryota Hasegawa, Miu Hirano, Takeyuki Tsuji, Takayuki Iwasaki, Mutsuko Hatano, Kento Sasaki, Kensuke Kobayashi
Mesoscale and Nanoscale Physics
High-fidelity regimes of resonator-mediated controlled-Z gates between quantum-dot qubits
Guangzhao Yang, Marek Gluza, Si Yan Koh et al. (+6 more)
Semiconductor double
quantum dot (DQD)
qubits coupled via superconducting microwave resonators provide a powerful means of long-range manipulation of the
qubits'
spin and charge degrees of freedom.
Quantum gates can be implemented by parametrically driving the
qubits while their transition frequencies are detuned from the resonator frequency. Long-range two-
qubit controlled-Z (CZ) gates have been proposed for the DQD
spin qubit within the rotating-wave approximation (RWA). Rapid gates demand strong coupling, but RWA breaks down when coupling strengths become significant relative to system frequencies. Therefore, understanding the errors arising from approximations used is critical for high-fidelity operation. Here, we go beyond RWA to study CZ gate fidelity for both DQD
spin and charge
qubits. We propose a novel parametric drive on the charge
qubit that produces smaller errors and show that the fidelity of the CZ gate outperforms its
spin counterpart, resulting in a much smaller fidelity loss of $0.05\%$ compared to $0.80\%$ for the
spin qubit, and greater robustness against
qubit dephasing and
photon loss. We find that drive amplitude – a parameter dropped in RWA – is critical for optimizing fidelity, with the charge
qubit exhibiting better tolerance to drive amplitude variations. Our results demonstrate the necessity of going beyond RWA in understanding how long-range gates can be realized in DQD
qubits, with charge
qubits offering considerable advantages in high-fidelity operation.
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All authors Guangzhao Yang, Marek Gluza, Si Yan Koh, Kelvin Onggadinata, Calvin Pei Yu Wong, Kuan Eng Johnson Goh, Bent Weber, Hui Khoon Ng, Teck Seng Koh
Strongly Correlated Electrons
Evidence for itinerant electron-local moment interaction in Li-doped $\alpha$-MnTe
Tingjun Zhang, Steven J. Gomez Alvarado, Sijie Xu et al. (+17 more)
We use inelastic
neutron scattering (INS) and angle-resolved photoemission spectroscopy (ARPES) to study the impact of Li doping on the semiconducting altermagnet $\alpha$-MnTe. Introducing Li results in a
spin reorientation from in-plane to out-of-plane direction and increases the density of itinerant carriers. While our ARPES measurements do not indicate any notable doping-induced changes in the electronic band structure or the magnitude of the altermagnetic band splitting, our INS measurements reveal an abrupt carrier-induced decrease in the
spin wave lifetime near the zone boundary at high energies. This finding is consistent with a new
magnon decay channel driven by doping-induced subtle changes in the band structure and enhanced interactions between Mn$^{2+}$ local moments and itinerant electrons. By extracting the local dynamic susceptibility from INS spectra and applying the total moment sum rule, we find that both undoped and Li-doped $\alpha$-MnTe exhibit the full expected Mn$^{2+}$ local moment of $\approx5.9~\mu_\mathrm{B}$ with $S=5/2$. These findings suggest that $\alpha$-MnTe hosts robust local-moment altermagnetism which shows a breakdown at high energies upon addition of itinerant carriers, highlighting the importance of carrier-
spin coupling in magneto-transport and
spin dynamic properties of altermagnets even in the dilute-carrier limit.
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All authors Tingjun Zhang, Steven J. Gomez Alvarado, Sijie Xu, Thomas Hulse, Travis J. Williams, Xiaoping Wang, Junhong He, Matthew B. Stone, Colin Sarkis, Feng Ye, Zhaoyu Liu, Jinyulin Li, Aparna Jayakumar, Zehao Wang, Yaofeng Xie, Ching-Wu Chu, Liangzi Deng, Emilia Morosan, Ming Yi, Pengcheng Dai
Strongly Correlated Electrons
Signatures of bi-altermagnetism revealed by sublattice-specific circular dichroism in resonant inelastic X-ray scattering
G. Channagowdra, A. Singh, H. Y. Huang et al. (+9 more)
An altermagnet is a recently identified class of magnets that exhibit a zero net
magnetic moment but break
symmetry under the combined operations of parity and time reversal. It typically consists of two
magnetic sites of opposite
spins related by rotation within the unit
cell. Here, we use circular dichroism (CD) in resonant inelastic X-ray scattering (RIXS) to reveal
symmetry signatures of a distinct form of altermagnetism, namely bi-altermagnetism, in the correlated
insulator Fe2Mo3O8, which comprises two altermagnetic sublattices: one with alternating quasi-octahedral Fe environments and the other with alternating tetrahedral Fe environments. We experimentally revealed the emergence of CD in an achiral, zero-magnetization system, thereby probing mirror-
symmetry breaking associated with altermagnetic order. Notably, the CD appeared at sublattice-specific excitations of the octahedral and tetrahedral sites, indicating
symmetry breaking in both altermagnetic sublat- tices. Calculations based on a model with the bi-altermagnetic order along the c axis successfully reproduce the observed CD. Our findings support the realization of bi-altermagnetism in Fe2Mo3O8, and showcase the use of RIXS-CD as a probe of
magnetic sublattices in systems with zero net magnetization.
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All authors G. Channagowdra, A. Singh, H. Y. Huang, M. Furo, Bin Gao, Pengcheng Dai, C.T. Chen, J. Kunes, A. Fujimori, S-W. Cheong, A. Hariki, D. J. Huang
Materials Science · Cross-listed from physics.app-ph
New record in optical gain and room-temperature nanolasers in multiple wavelengths in 2D ErOCl single crystals
Shipeng Yao, Hao Sun, Zhang Liang et al. (+5 more)
Erbium-based materials have long been recognized for their important telecom-band applications, yet their widespread adoption in integrated optoelectronics has been hindered by two fundamental limitations: the difficulty in achieving high erbium density without concentration quenching which leads to small optical gain in doped materials, and the difficulty in fabricating a practical device with single
crystal nanowires that demonstrated high optical gain previously1,2. Here, we overcome these limitations by synthesizing 2D single
crystal ErOCl that has an Er density of 1.75*1022 cm-3. The high-quality single
crystal material significantly reduces the density-related quenching effect that dominates in randomly doped materials with high Er concentration. This results in a record optical gain coefficient over 1500 dB/cm at 1536 nm band, at least larger by an order of magnitude than the previous gain record in Er materials. Leveraging this exceptional gain medium, we demonstrate room-temperature continuous-wave lasing operation by integrating with a photonic
crystal microcavity, achieving a record-low threshold of 7 {\mu}W with the most compact size of any Er-based
lasers. Furthermore, the unique Stark splitting characteristics of ErOCl provide optical gain in three wavelength bands and lead to lasing in these wavelengths by engineering the cavity. This is the first time that optical gain has been shown in three different wavelength bands in Er materials, together with the smallest size of
laser cavity, could have many important applications in on-chip sensing and optical communication.
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All authors Shipeng Yao, Hao Sun, Zhang Liang, Zhen Wang, Lin Gan, Jinhua Wu, Zhangyu Hou, Cun-Zheng Ning
Materials Science
First-principles calculations of elasto-optical properties of $R$Te$_3$
Kuiqing Tang
Rare-earth tritellurides ($R$Te$_3$) exhibit complex charge-density-wave (CDW) phases intertwined with
lattice symmetry, offering a platform to explore unconventional
symmetry breaking in correlated materials. Elasto-optical probing, which detects strain-induced changes in birefringence, provides a non-invasive approach to visualize anisotropy and emergent order in these quasi-two-dimensional systems. However, the magnitude and
symmetry of the expected optical response remain poorly quantified, hindering experimental interpretation. Here, we perform first-principles calculations of the elastic, dielectric, and piezo-optical tensors of NdTe$_3$ to establish a quantitative framework for strain-induced optical anisotropy. These results establish a quantitative link between
lattice strain and optical response in $R$Te$_3$, providing a predictive framework for probing
symmetry-breaking states via elasto-birefringence.
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Statistical Mechanics · Cross-listed from hep-th
No boundary density matrix in elliptic de Sitter dS/$\mathbb{Z}_2$
Raphaël Dulac and Zixia Wei
Elliptic de Sitter (dS) spacetime dS$/\mathbb{Z}_2$ is a non-time-orientable spacetime obtained by imposing an antipodal identification to global dS. Unlike QFT on global dS, whose
vacuum state can be prepared by a no-boundary Euclidean path integral, the Euclidean
elliptic dS does not define a wavefunction in the usual sense. We propose instead that the path integral on the Euclidean
elliptic dS defines a no-boundary density
matrix. As an explicit example, we study the free Dirac
fermion CFT in two-dimensional
elliptic dS and analytically compute the von Neumann and the Rényi
entropies of this density
matrix. The calculation reduces to correlation functions of vertex operators on non-orientable surfaces. As a by-product, we compute the time
evolution of
entanglement entropy following a crosscap quench in free Dirac
fermion CFT. We also comment on a striking feature of free QFT in
elliptic dS: its global
Hilbert space is one-dimensional, wheres the
Hilbert space associated to each observer is a nontrivial Fock space.
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Materials Science
A Dimensionally Consistent Size-Strain Plot Method for Crystallite Size and Microstrain Estimation
Anand Pal
X-ray diffraction (XRD) peak broadening analysis remains a cornerstone for quantifying crystallite size and
lattice microstrain in materials. Among various approaches, the Size Strain Plot (SSP) method is widely employed for its conceptual simplicity and ease of use. However, this study reveals that the equation most commonly applied in SSP analysis is dimensionally inconsistent, a critical flaw that has gone largely unnoticed and replicated across decades of materials research. This pervasive error raises concerns about the validity of a significant body of published microstructural data. By tracing the historical origin of the misformulated equation, we demonstrate how a seemingly minor oversight evolved into a widely accepted standard practice within the field. We then present a dimensionally consistent formulation that restores physical meaning and analytical reliability to the SSP method. The corrected framework re-establishes the SSP approach as a robust and physically valid tool for XRD-based microstructural characterization. \en
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