Materials Science
Electrically and optically active charge carrier traps in silicon-doped few-layer GaSe
M. Bissolo, R. Li, M. Ogura et al. (+9 more)
Understanding defects in atomically thin van der Waals (vdW)
semiconductors is essential for advancing their use in next-generation optoelectronic and photovoltaic devices. Here, we apply a combination of various impedance spectroscopy techniques to two-dimensional (2D) vdW GaSe doped with silicon (Si) to reconstruct deep trap states across the full bandgap. Deep-level transient spectroscopy reveals three distinct deep states 0.31, 0.88, and 1.40 eV below the conduction band edge. Complementary deep-level optical spectroscopy and photocapacitance measurements identify three deep states at 1.4 and 1.8 eV below the conduction band edge, and 2.0 eV above the valence band edge, with thermal admittance spectroscopy providing additional verification and further resolving two trap states, at 0.16 eV above the valence band edge and at 0.26 eV below the conduction band edge. By comparing the experimentally extracted ionization energies with the predictions of density functional theory, our results attribute these trap states primarily to Si-related defects and metal vacancies. This work presents a comprehensive defect map of Si-doped GaSe, providing critical insights into carrier trapping mechanisms that are essential for optimizing the design of 2D material-based devices for industrial applications.
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All authors M. Bissolo, R. Li, M. Ogura, Z. Sofer, S. Polesya, D. Han, A. W. Holleitner, C. Kastl, G. Koblmüller, H. Ebert, E. Zallo, J. J. Finley
Materials Science
Observation of a structurally driven, reversible topological phase transition in a distorted square net material
Xian P. Yang, Chia-Hsiu Hsu, Gokul Acharya et al. (+14 more)
Topological materials hold immense promise for exhibiting exotic
quantum phenomena, yet achieving controllable topological phase transitions remains challenging. Here, we demonstrate a structurally driven, reversible topological phase transition in the distorted square net material GdPS, induced via in situ potassium dosing. Using angle-resolved photoemission spectroscopy and first principles calculations, we demonstrate a cascade of topological phases in the sub-surface P layer: from a large, topologically trivial band gap to a gapless Dirac cone state with a 2 eV dispersion, and finally to a two-dimensional topological
insulator as inferred from theory. This
evolution is driven by subtle structural distortions in the first P layer caused by potassium adsorption, which in turn contribute to the band gap closure and topological phase transition. Furthermore, the ability to manipulate the
topology of a sub-surface layer in GdPS offers a unique route for exploring and controlling topological states in bulk materials.
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All authors Xian P. Yang, Chia-Hsiu Hsu, Gokul Acharya, Junyi Zhang, Md Shafayat Hossain, Tyler A. Cochran, Bimal Neupane, Zi-Jia Cheng, Santosh Karki Chhetri, Byunghoon Kim, Shiyuan Gao, Yu-Xiao Jiang, Maksim Litskevich, Jian Wang, Yuanxi Wang, Jin Hu, M. Zahid Hasan
Strongly Correlated Electrons
Revealing the microscopic origin of the magnetization plateau in Na$_3$Ni$_2$BiO$_6$
Amanda A. Konieczna, P. Peter Stavropoulos and Roser Valentí
Recent experimental studies of the
spin-1 honeycomb antiferromagnet Na$_3$Ni$_2$BiO$_6$ have revealed a pronounced one-third magnetization plateau under applied
magnetic fields, highlighting the presence of strong
magnetic frustration and anisotropy in this material. Such behavior has been attributed to substantial bond-dependent Kitaev interactions in combination with single-ion anisotropy, placing Na$_3$Ni$_2$BiO$_6$ among honeycomb compounds of interest for unconventional
magnetic phases. Motivated by these observations, we present a first-principles-based analysis of the
magnetic interactions in Na$_3$Ni$_2$BiO$_6$. By combining density-functional calculations with microscopic modeling, we extract the relevant exchange parameters and construct an effective
spin model that quantitatively reproduces both the elastic
neutron-scattering spectra and the magnetization curve. The model captures the experimentally observed zero-field zigzag
magnetic order, and proposes a $\textit{double-zigzag}$ state at intermediate
magnetic fields, realizing the 1/3-magnetization plateau in a simpler way than suggested in previous works. Crucially, we show that the one-third magnetization plateau does not require Kitaev interactions; instead, it arises from the interplay of strong out-of-plane single-ion anisotropy and competing
ferromagnetic nearest-neighbor ($J_1$) and
antiferromagnetic third-neighbor ($J_3$) Heisenberg couplings. These results establish a consistent microscopic description of Na$_3$Ni$_2$BiO$_6$ and clarify the origin of its field-induced plateau phase.
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Mesoscale and Nanoscale Physics
First-Principles AI finds crystallization of fractional quantum Hall liquids
Ahmed Abouelkomsan and Liang Fu
When does a fractional
quantum Hall (FQH)
liquid crystallize? Addressing this question requires a framework that treats fractionalization and crystallization on equal footing, especially in strong Landau-level mixing regime. Here, we introduce MagNet, a self-
attention neural-network variational wavefunction designed for
quantum systems in
magnetic fields on the
torus geometry. We show that MagNet provides a unifying and expressive ansatz capable of describing both FQH states and electron
crystals within the same architecture. Trained solely by energy minimization of the microscopic
Hamiltonian, MagNet discovers topological
liquid and electron
crystal ground states across a broad range of Landau-level mixing. Our results highlight the power of first-principles AI for solving strongly interacting many-body problems and finding competing phases without external training data or physics pre-knowledge.
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Strongly Correlated Electrons
Primary charge-4e superconductivity from doping a featureless Mott insulator
Zhi-Qiang Gao, Yan-Qi Wang, Ya-Hui Zhang et al. (+1 more)
Superconductivity is usually understood as a phase in which charge-$2e$ Cooper pairs are condensed. Charge-$4e$ superconductivity has largely been discussed as a vestigial order at finite temperature emerging from charge-$2e$ states. Primary charge-$4e$ superconducting phases at zero temperature remain scarce in both experiments and microscopic models. Here we argue that a doped featureless Mott
insulator with $SU(4)$
symmetry provides a natural platform for primary charge-$4e$ superconductivity, based on perturbative renormalization group arguments and group theoretic considerations. As a concrete realization, we construct a
bilayer Hubbard model with tunable onsite $SU(4)$ and $Sp(4)$
symmetries that exhibits a featureless Mott insulating phase at half filling. Its low energy physics is captured by a generalized ESD model, featuring an effective
Hamiltonian that is purely kinetic within the constrained
Hilbert space. Using density
matrix renormalization group (DMRG) simulations, we find a primary charge-$4e$ superconducting phase in the $SU(4)$ ESD model and a conventional primary charge-$2e$ phase in the $Sp(4)$ case. We further characterize the corresponding normal states and discuss the resulting finite temperature phase diagram.
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All authors Zhi-Qiang Gao, Yan-Qi Wang, Ya-Hui Zhang, Hui Yang
Statistical Mechanics
Tsallis Entropy derived from the Chaitin-Kolmogorov Informational Entropy
Airton Deppman
We provide a rigorous first-principle derivation of the non-additive Tsallis'
entropy by employing the Chaitin-Kolmogorov algorithmic information theory. By applying non-local restrictive rules on the string formation (grammar), we show that the algorithmic cost follows a power-law of the string length, instead of the linear behaviour obtained in the classical theory. As a result, the Tsallis
entropy governs the increase of information. We explore the result showing, through Landauer's limit, that the heat dissipation in systems with long-range correlations is diminished. The $\Omega_q$ number, which remains incompressible, now offers the possibility of a continuous increase of complexity, measured by the parameter $q$. We show the consistency of the results by a numerical simulation, and discuss Zipf's law in light of the new findings.
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Mesoscale and Nanoscale Physics
Optical detection of the quantum Hall effect in silicon nanostructures
N.T. Bagraev, L.E. Klyachkin, A.N. Malyarenko et al. (+1 more)
Electroluminescence spectra of a silicon nanostructure with edge channels covered by chains of dipole centers with negative correlation energy are demonstrated. The presence of such chains provides conditions for nondissipative transport of single charge carriers at high temperatures up to room temperature. Due to the suppression of the electron-electron interactions, the macroscopic
quantum phenomena such as Shubnikov - de Haas oscillations and the
quantum staircase of
Hall resistance are consistent with the positions of the spectral peaks of the detected electroluminescence. The obtained results are considered in the framework of Faraday electromagnetic induction, which indicates that Landau quantization leads to the emergence of induced irradiation similar to Josephson and Andreev generation. Moreover, the detected maxima in the spectral characteristics correspond to odd fractional values of the resistance
quantum staircases, while the dips in the electroluminescence spectra are observed at even fractional values of the resistance
quantum ladder, which is due to the increased formation of composite
bosons and
fermions, respectively.
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All authors N.T. Bagraev, L.E. Klyachkin, A.N. Malyarenko, N.I. Rul'
Strongly Correlated Electrons
A Unified Categorical Description of Quantum Hall Hierarchy and Anyon Superconductivity
Donghae Seo, Taegon Lee and Gil Young Cho
We present a unified category-theoretic framework for
quantum Hall hierarchy constructions and anyon superconductivity based on modular tensor categories over $\mathrm{Rep}(\mathrm{U}(1))$ and $\mathrm{sRep}(\mathrm{U}(1)^f)$. Our approach explicitly incorporates conserved $\mathrm{U}(1)$ charge and formulates doping via a generalized stack-and-condense procedure, in which an auxiliary topological order is stacked onto the parent phase, and the quasiparticles created by doping subsequently condense. Depending on whether this condensation preserves or breaks the $\mathrm{U}(1)$
symmetry, the system undergoes a transition to a
quantum Hall hierarchy state or to an anyon
superconductor. For anyon
superconductors, the condensate charge is determined unambiguously by the charged local
bosons contained in the condensable
algebra. Our framework reproduces all known anyon
superconductors obtained from field-theoretic analyses and further predicts novel phases, including a charge-$2e$ anyon
superconductor derived from the Laughlin state and charge-$ke$ anyon
superconductors arising from bosonic $\mathbb{Z}_k$ Read-Rezayi states. By placing hierarchy transitions and anyon superconductivity within a single mathematical formalism, our work provides a unified understanding of competing and proximate phases near experimentally realizable fractional
quantum Hall states.
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Strongly Correlated Electrons
Classical Benchmarks of a Symmetry-Adapted Variational Quantum Eigensolver for Real-Time Green's Functions in Dynamical Mean-Field Theory
Aadi Singh, Chakradhar Rangi and Ka-Ming Tam
We present a variational
quantum eigensolver (VQE) approach for solving the Anderson
Impurity Model (AIM) arising in Dynamical Mean-Field Theory (DMFT). Recognizing that the minimal two-site approximation often fails to resolve essential spectral features, we investigate the efficacy of VQE for larger bath discretizations while adhering to near-term hardware constraints. We employ a
symmetry-adapted ansatz enforcing conservation of particle number $(N)$,
spin projection $(S_z=0)$, and total
spin $(S^2=0)$
symmetry, benchmarking the performance against exact diagonalization across different interaction strengths using bath parameters extracted from the DMFT self-consistency loop. For a four-site model, the relative error in the ground state energy remains well below $0.01%$ with a compact parameter set $(N_p \le 30)$. Crucially, we demonstrate that the single-particle Green's function-the central quantity for DMFT-can be accurately extracted from VQE-prepared ground states via real-time
evolution in the intermediate to strong interaction regimes. However, in the weak interaction regime, the Green's function exhibits noticeable deviations from the exact
benchmark, particularly in resolving low-energy spectral features, despite the ground state energy showing excellent agreement. These findings demonstrate that VQE combined with real-time
evolution can effectively extend
quantum-classical hybrid DMFT beyond the two-site approximation, particularly for describing insulating phases. While this approach offers a viable pathway for simulating strongly correlated materials on near-term devices, the observation that accurate ground state energy does not guarantee accurate dynamical properties highlights a key challenge for applying such approaches to correlated metals.
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Quantum Gases
Temperature driven false vacuum decay in coherently coupled Bose superfluids
Paniyanchatha Moolayil Sivasankar, Franco Dalfovo, Alessio Recati et al. (+1 more)
The relaxation of a
quantum field from a metastable state (false
vacuum) to a stable one (true
vacuum), also known as false
vacuum decay, is a fundamental problem in
quantum field theory and cosmology. We study this phenomenon using a two-dimensional interacting and coherently coupled Bose-Bose mixture, a platform that has already been employed experimentally to investigate false
vacuum decay in one dimension. In such a mixture, it is possible to define an effective magnetization that acts as a
quantum field variable. Using the
Stochastic Gross-Pitaevskii equation (SGPE), we prepare thermal
equilibrium states in the false
vacuum and extract decay rates from the magnetization dynamics. The decay rates show an exponential dependence on temperature, in line with the thermal theory of instantons. Since the SGPE is based on complex scalar fields, it also allows us to explore the behavior of the phase, which turns out to become dynamic during decay. Our results confirm the SGPE as an effective tool for studying coupled magnetization and phase dynamics and the associated instanton physics in ultracold
quantum gases.
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All authors Paniyanchatha Moolayil Sivasankar, Franco Dalfovo, Alessio Recati, Arko Roy
Soft Condensed Matter
Vacancy defects in square-triangle tilings and their implications for quasicrystals formed by square-shoulder particles
Alptuğ Ulugöl, Giovanni Del Monte, Eline K. Kempkes et al. (+2 more)
Almost all observed square-triangle quasicrystals in soft-matter systems contain a large number of point-like defects, yet the role these defects play in stabilizing the quasicrystal phase remains poorly understood. In this work, we investigate the thermodynamic role of such defects in the widely observed 12-fold symmetric square-triangle quasicrystal. We develop a new Monte Carlo simulation to compute the configurational
entropy of square-triangle tilings augmented to contain two types of irregular hexagons as defect tiles. We find that the introduction of defects leads to a notable
entropy gain, with each defect contributing considerably more than a conventional vacancy in a periodic
crystal. Intriguingly, the
entropy gain is not simply due to individual defect types but isamplified by their combinatorial mixing. We then apply our findings to a microscopic model of core-corona particles interacting via a square-shoulder potential. By combining the configurational
entropy with vibrational free-energy calculations, we predict the
equilibrium defect concentration and confirm that the quasicrystalline phase contains a higher concentration of point-defects than a typical periodic
crystal. These results provide a new understanding of the prominence of observed defects in soft-matter quasicrystals.
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All authors Alptuğ Ulugöl, Giovanni Del Monte, Eline K. Kempkes, Frank Smallenburg, Laura Filion
Materials Science
Origin of mixed anisotropy in crystalline Permalloy and amorphous Cobalt thin films individually deposited on Si substrate
Kirti Kirti, Baisali Ghadai, Abinash Mishra et al. (+2 more)
Magnetic anisotropy (MA) plays a crucial role in deciding both static and dynamic behaviour of
magnetic thin films. It controls various phenomena, such as magnetization reversal, domain formation, domain-wall motion,
spin-wave generation, and
spin-wave propagation etc. We investigate the mixed anisotropies in face-centred-cubic Permalloy (fcc-Py) and amorphous Cobalt (a-Co) thin films deposited via rf magnetron sputtering on Si (100) substrate with thicknesses, d = 5-125 nm and t = 5-150 nm, respectively. X-ray diffraction technique, atomic force microscopy, and vibrating sample magnetometry are employed to study the structural, morphological, and
magnetic properties. We adopt a qualitative approach to understand the nature of different anisotropies present in both materials. Mixed anisotropies evolve with film thicknesses for both fcc-Py and a-Co films. The role of growth conditions in the emergence of specific anisotropies is discussed in detail. An alteration of the magnetization easy axis from the conventional in-plane orientation is evidenced due to the collective influence of these mixed anisotropies. Based on the dominance of anisotropy components, their origin, and the direction of magnetization tilt, we categorize our samples as belonging to specific regimes. Introduction of magnetization tilt has been proven to be an extremely innovative way to improve the performance of spintronic devices so far. The one-to-one comparison between a sputter-deposited crystalline and an amorphous
magnetic material could be beneficial for building a stronger foundation for that.
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All authors Kirti Kirti, Baisali Ghadai, Abinash Mishra, Rahulkrishnan R, Sucheta Mondal
Statistical Mechanics
Emergent correlations in the selected link-times along optimal paths
Iván Álvarez Domenech, Javier Rodríguez-Laguna, Pedro Córdoba-Torres et al. (+1 more)
In the context of first-passage percolation (FPP), we investigate the statistical properties of the selected link-times (SLTs) -the random link times comprising the optimal paths (or geodesics) connecting two given points. We focus on weakly disordered square
lattices, whose geodesics are known to fall under the Kardar-Parisi-Zhang (KPZ) universality class. Our analysis reveals universal power-law decays with the end-to-end distance for both the average and standard deviation of the SLTs, along with an intricate pattern of long-range correlations, whose scaling exponents are directly linked to KPZ universality. Crucially, the SLT distributions for diagonal and axial paths exhibit significant differences, which we trace back to the distinct directed and undirected nature, respectively, of the underlying geodesics. Moreover, we demonstrate that the SLT distribution violates the conditions of the central limit
theorem. Instead, SLT sums follow the Tracy-Widom distribution characteristic of the KPZ class, which we associate with evidence for the emergence of high-order long-range correlations in the ensemble.
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All authors Iván Álvarez Domenech, Javier Rodríguez-Laguna, Pedro Córdoba-Torres, Silvia N. Santalla
Statistical Mechanics
The Mpemba effect in the Descartes protocol: A time-delayed Newton's law of cooling approach
Andrés Santos
We investigate the direct and inverse Mpemba effects within the framework of the time-delayed Newton's law of cooling by introducing and analyzing the Descartes protocol, a three-reservoir thermal scheme in which each sample undergoes a single-step quench at different times. This protocol enables a transparent separation of the roles of the delay time $\tau$, the waiting time $t_{\text{w}}$, and the normalized warm temperature $\omega$, thus providing a flexible setting to characterize anomalous thermal relaxation. For instantaneous quenches, exact conditions for the existence of the Mpemba effect are obtained as bounds on $\omega$ for given $\tau$ and $t_{\text{w}}$. Within those bounds, the effect becomes maximal at a specific value $\omega=\widetilde{\omega}(t_{\text{w}})$, and its magnitude is quantified by the extremal value of the temperature-difference function at this optimum. Accurate and compact approximations for both $\widetilde{\omega}(t_{\text{w}})$ and the maximal magnitude $\text{Mp}(t_{\text{w}})$ are derived, showing in particular that the absolute maximum at fixed $\tau$ is reached for $t_{\text{w}}=\tau$. A comparison with a previously studied two-reservoir protocol reveals that, despite its additional control parameter, the Descartes protocol yields a smaller maximal magnitude of the effect. The analysis is extended to finite-rate quenches, where strict equality of bath conditions prevents a genuine Mpemba effect, although an approximate one survives when the bath time scale is sufficiently short. The developed framework offers a unified and analytically tractable approach that can be readily applied to other multi-step thermal protocols.
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Quantum Gases
Structures and proximity effects of inhomogeneous population-imbalanced Fermi gases with pairing interactions
Bishal Parajuli, Devin J. Gagnon and Chih-Chun Chien
By introducing spatially varying profiles of pairing interaction or
spin polarization to quasi one-dimensional two-component atomic
Fermi gases confined in box potentials, we analyze the ground state structures and properties when multiple phases coexist in real space by implementing the Bogoliubov–de~Gennes equation suitable for describing inhomogeneous
fermion systems. While the BCS, Fulde–Ferrell–Larkin–Ovchinnikov (FFLO), and normal phases occupy different regions on the phase diagram when the parameters are uniform, a spatial change of pairing strength or
spin polarization can drive the system from the FFLO phase to a normal gas or from a BCS superfluid to the FFLO phase in real space. The FFLO phase exhibits its signature modulating order parameter at the FFLO momentum due to population imbalance, and the pair correlation penetrates the polarized normal phase and exhibits proximity effects. Meanwhile, the BCS phase tends to repel population imbalance and maintain a plateau of pairing. Interestingly, a buffer FFLO phase emerges when the spatial change attempts to join the BCS and normal phase in the presence of
spin polarization. By analyzing the pairing correlations, interfacial properties, and momentum-space spectra of the inhomogeneous structures, relevant length- and momentum- scales and their interplay are characterized. We also briefly discuss implications of inhomogeneous multi-phase atomic
Fermi gases with population imbalance.
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Materials Science
Polytype-Dependent Upconversion Photoluminescence in 3R-MoS2
Omri Meron, Idan Kizel, Dror Hershkovitz et al. (+6 more)
Ferroelectric van der Waals materials offer switchable polarization states, yet optical readout of their stacking configurations remains challenging. Here, building on the resonant
exciton-
exciton annihilation (EEA) mechanism recently identified in 2H-phase TMDs, we report the first observation of upconversion photoluminescence (UPL) in rhombohedral MoS$_2$ and demonstrate that this many-body process is strongly polytype-dependent. Using low-temperature spectroscopy, we observe anti-Stokes emission with superlinear power dependence characteristic of EEA. Beyond serving as an accurate layer-number sensor due to discrete bandgap variations, UPL provides a sensitive probe of stacking order across thicknesses. The two neutral trilayer polytypes, which remain indistinguishable by surface potential measurements and second harmonic generation, exhibit markedly different UPL intensities. This sensitivity persists in thicker samples where multiple configurations coexist. First-principles calculations suggest that the intensity contrast originates primarily from the layer confinement of the annihilating
excitons, while energy matching to the $\Gamma$ final-state
manifold provides additional intensity selectivity. Power-dependent spectroscopy further disentangles two distinct annihilation channels originating from different dark
exciton valleys, identified through their contrasting intensity scaling and opposite density-induced energy shifts. Crucially, the annihilation process doubles the energy separation of nearly degenerate dark
excitons while converting their weak emission into bright signal, providing experimental access to valley-specific responses that are obscured in direct dark-
exciton spectroscopy. Our findings demonstrate that ferroelectric configurations provide a new degree of freedom for controlling nonlinear optical processes.
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All authors Omri Meron, Idan Kizel, Dror Hershkovitz, Youngki Yeo, Nirmal Roy, Wei Cao, Alon Ron, Moshe Ben Shalom, Haim Suchowski
Strongly Correlated Electrons
Spin and Charge Conductivity in the Square Lattice Fermi-Hubbard Model
Linh Pham and Ehsan Khatami
Dynamical properties are notoriously difficult to compute in numerical treatments of the
Fermi-Hubbard model, especially in two spatial dimensions. However, they are essential in providing us with insight into some of the most important and less well-understood phases of the model, such as the pseudogap and strange metal phases at relatively high temperatures, or unconventional superconductivity at lower temperatures, away from the commensurate filling. Here, we use the numerical linked-cluster expansions to compute
spin and charge optical conductivities of the model at different temperatures and strong interaction strengths via the exact real-time-dependent correlation functions of the current operators. We mitigate systematic errors associated with having a limited access to the long-time behavior of the correlators by introducing fits and allowing for non-zero Drude weights when appropriate. We compare our results to available data from optical
lattice experiments and find that the Drude contributions can account for the theory-experiment gap in the DC
spin conductivity of the model at half filling in the strong-coupling region. Our method helps paint a more complete picture of the conductivity in the two-dimensional Hubbard model and opens the door to studying dynamical properties of
quantum lattice models in the thermodynamic limit.
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Soft Condensed Matter
Ultrastable 2D glasses and packings explained by local centrosymmetry
A. Zaccone
Using the most recent numerical data by Bolton-Lum et al. [Phys. Rev. Lett. 136, 058201 (2026)], we demonstrate that ideal ultrastable glasses in the athermal limit (or ultrastable ideal 2D disk packings) possess a remarkably high degree of local centrosymmetry. In particular, we find that the inversion-
symmetry order parameter for local force transmission introduced in Milkus and Zaccone, [Phys. Rev. 93, 094204 (2016)], is as high as $F_{IS}= 0.84522$, to be compared with $F_{IS}=1$ for perfect centrosymmetric
crystals free of defects, and with $F_{IS} \sim 0.3-0.5$ for standard random packings. This observation provides a clear, natural explanation for the ultra-high shear modulus of ideal packings and ideal glasses, because the high centrosymmetry prevents non-affine relaxations which decrease the shear modulus. The same mechanism explains the absence of
boson peak-like soft vibrational modes. These results also confirm what was found previous work, i.e. that the bond-orientational order parameter is a very poor correlator for the vibrational and mechanical
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Statistical Mechanics · Cross-listed from quant-ph
Accelerating qubit reset through the Mpemba effect
Théo Lejeune, Miha Papič, John Goold et al. (+3 more)
Passive
qubit reset is a key primitive for
quantum information processing, whereby
qubits are initialized by allowing them to relax to their ground state through natural dissipation, without the need for active control or feedback. However, passive reset occurs on timescales that are much longer than those of gate operations and measurements, making it a significant bottleneck for algorithmic execution. Here, we show that this limitation can be overcome by exploiting the Mpemba effect, originally indicating the faster cooling of hot systems compared to cooler ones. Focusing on the regime where coherence times exceed energy relaxation times ($T_2 > T_1$), we propose a simple protocol based on a single entangling two-
qubit gate that converts local single-
qubit coherences into fast-decaying global two-
qubit coherences. This removes their overlap with the slowest decaying Liouvillian mode and enables a substantially faster relaxation to the ground state. For realistic parameters, we find that our protocol can reduce reset times by up to $50\%$ compared to standard passive reset. We analyze the robustness of the protocol under non-Markovian noise, imperfect coherent control and finite temperature, finding that the accelerated reset persists across a broad range of realistic error sources. Finally, we present an experimental implementation of our protocol on an IQM superconducting
quantum processor. Our results demonstrate how Mpemba-like accelerated relaxation can be harnessed as a practical tool for fast and accurate
qubit initialization.
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All authors Théo Lejeune, Miha Papič, John Goold, Felix C. Binder, François Damanet, Mattia Moroder
Statistical Mechanics
Pedro V. Paraguassú
Quantum-Induced
Stochastic Dynamics arises from the coupling between a classical system and a
quantum environment. Unlike standard thermal reservoirs, this environment acts as a dynamic bath, capable of simultaneously exchanging heat and performing work. We formulate a thermodynamic framework for this semi-classical regime, defining heat, work, and
entropy production. We derive a modified Second Law that accounts for non-
equilibrium quantum features, such as squeezing. The framework is exemplified by an optomechanical setup, where we characterize the thermodynamics of the non-stationary noise induced by the cavity field.
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Strongly Correlated Electrons
Machine Learning Modeling of Charge-Density-Wave Recovery After Laser Melting
Sankha Subhra Bakshi, Yunhao Fan and Gia-Wei Chern
We investigate the nonequilibrium dynamics of a
laser-pumped two-dimensional spinless Holstein model within a semiclassical framework, focusing on the melting and recovery of long-range charge-density-wave order. Accurately describing this process requires fully nonadiabatic electron-
lattice dynamics, which is computationally demanding due to the need to resolve fast electronic motion over long time scales. By analyzing the structure of the
lattice force during nonequilibrium
evolution, we show that the force naturally separates into a smooth quasi-adiabatic component and a residual bath-like contribution associated with fast electronic fluctuations. The quasi-adiabatic component depends only on the instantaneous local
lattice configuration and can be efficiently learned using machine-learning techniques, while a minimal Langevin description of the bath term captures the essential features of the recovery dynamics. Combining these elements enables efficient and scalable simulations of long-time nonequilibrium dynamics on large
lattices, providing a practical route to access driven correlated systems beyond the reach of direct nonadiabatic approaches.
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Materials Science · Cross-listed from physics.comp-ph
Transformation front kinetics in deformable ferromagnets
Michael Poluektov
Materials such as
magnetic shape-
memory alloys possess an intrinsic coupling between material's magnetisation and mechanical deformation. These materials also undergo structural phase transitions, with phase boundaries separating different phases. The kinetics of the phase boundaries is governed by the
magnetic field and the mechanical stresses. There is a multiplicity of other materials revealing similar phenomena, e.g.\
magnetic perovskites. To model the propagation of the phase boundaries in deformable
magnetic materials at the continuum scale, three ingredients are required: a set of governing equations for the bulk behaviour with coupled
magnetic and mechanical degrees of freedom, a dependency of the phase boundary velocity on the governing factors, and a reliable computational method. The expression for the phase boundary velocity is usually obtained within the continuum thermodynamics setting, where the
entropy production due to phase boundary propagation is derived, which gives a thermodynamic driving force for the phase boundary kinetics. For deformable ferromagnets, all three elements (bulk behaviour, interface kinetics, and computational approaches) have been explored, but under a number of limitations. The present paper focuses on the derivation of the thermodynamic driving force for transformation fronts in a general magneto-mechanical setting, adapts the cut-finite-element method for transformation fronts in magneto-mechanics, which allows for an exceptionally efficient handling of the propagating interfaces, without modifying the finite-element mesh, and applies the developments to qualitative modelling of magneto-mechanics of
magnetic shape-
memory alloys.
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Quantum Gases
Emergence of magnetic excitations in one-dimensional quantum mixtures under confinement
Pablo Capuzzi, Patrizia Vignolo, Anna Minguzzi et al. (+1 more)
We obtain an exact solution for the spectral function for one-dimensional Bose-Bose and
Fermi-
Fermi mixtures with strong repulsive interactions, valid in arbitrary confining potentials and at all frequency scales. For the case of harmonic confinement we show that, on top of the ladder structure of the density excitations imposed by the external confinement,
spin excitations emerge as sideband peaks, with dispersion related to the one of
ferromagnetic or
antiferromagnetic spin chains and a width fundamentally larger for fermionic mixtures than for bosonic ones, as determined by the different
symmetry of
spin excited states. The observation of
spin excitation branches can provide a univocal probe of interaction-induced magnetism in ultracold atoms.
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All authors Pablo Capuzzi, Patrizia Vignolo, Anna Minguzzi, Silvia Musolino
Statistical Mechanics · Cross-listed from hep-th
Thermodynamics of the Heisenberg XXX chain with negative spin
Rong Zhong, Yang-Yang Chen, Kun Hao et al. (+2 more)
We study the thermodynamics of the isotropic Heisenberg XXX
spin chain with negative
spin, focusing on the case $s=-1$. The model is equivalent to the
quantum lattice nonlinear Schrödinger (NLS) model and appears as an effective theory in deep inelastic scattering in high-energy
quantum chromodynamics. Owing to its integrability, it admits a consistent Bethe Ansatz description and a well-defined thermodynamic limit. Using the thermodynamic Bethe Ansatz, we analyze the ground state, elementary excitations, and finite-temperature properties. In contrast to the conventional positive
spin XXX chain, the negative
spin model exhibits a distinct
vacuum structure and excitation spectrum, leading to modified TBA equations and unconventional low-temperature behavior. Although the integral equations resemble those of the Lieb-Liniger Bose gas, the thermodynamics and scaling properties are qualitatively different and cannot be continuously connected. We derive the free energy,
entropy, and specific heat, and identify a
quantum phase transition separating different thermodynamic regimes. At zero temperature, the excitation spectrum becomes linear in the continuum limit and can be described by a conformal field theory. The low-temperature regime realizes a Luttinger-
liquid like phase with features unique to the negative
spin XXX chain.
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All authors Rong Zhong, Yang-Yang Chen, Kun Hao, Wen-li Yang, Vladimir Korepin
Mesoscale and Nanoscale Physics
Stochastic Dynamics of Diffusive Memristor Blocks for Neuromorphic Computing
Wendy Otieno, Alex Gabbitas, Debi Pattnaik et al. (+3 more)
Biological systems use neural
circuits to integrate input information and produce outputs. Synaptic convergence, where multiple
neurons converge their inputs onto a single downstream
neuron, is common in natural neural
circuits. However, understanding specific computations performed by such neural blocks and implementating them in hardware requires further research. This work focuses on synaptic convergence in a simplified
circuit of three spiking artificial
neurons based on diffusive memristors. Numerical modelling and experiments reveal input voltage combinations that enable targeted activation of spiking for specific
neuron configurations. We analyse the statistical characteristics of spiking patterns and interpret them from a computational perspective. The numerical simulations match experimental measurements. Our findings contribute to development of universal functional blocks for neuromorphic systems.
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All authors Wendy Otieno, Alex Gabbitas, Debi Pattnaik, Pavel Borisov, Sergey Savel'ev, Alexander G. Balanov
Materials Science
Role of magnon-magnon interaction in optical excitation of coherent two-magnon modes
E.A. Arkhipova, A. E. Fedianin, I.A. Eliseyev et al. (+4 more)
Two-
magnon modes are terahertz-frequency
magnetic excitations in antiferromagnets, governed by exchange interactions, involving
magnons from the entire Brillouin zone and dominated by zone-edge
magnons. The ability to couple to light promotes two-
magnon modes as contenders for ultrafast optical manipulation of the
magnetic state, beyond conventional zone-center magnonics. While
magnon-
magnon interactions are known to critically shape the two-
magnon line in spontaneous Raman scattering spectra, their role in coherent time-domain excitations remains unexplored. We report a detailed experimental and theoretical study of the influence of
magnon-
magnon interactions on coherent two-
magnon modes in a cubic antiferromagnet excited via Impulsive Stimulated Raman scattering. We reveal the nontrivial
evolution of coherent
magnetic dynamics in the time domain and the corresponding spectrum and compare it with the spontaneous Raman scattering spectrum. By extending the
spin-correlations based theory for two-
magnon modes, we derive a unified description of their spectra in Raman Scattering and Impulsive Stimulated Raman Scattering and highlight the role of
magnon-
magnon interactions.
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All authors E.A. Arkhipova, A. E. Fedianin, I.A. Eliseyev, R.M. Dubrovin, P.P. Syrnikov, V.Yu. Davydov, A.M. Kalashnikova
Strongly Correlated Electrons
Orbital-selective Mottness Driven by Geometric Frustration of Interorbital Hybridization in Pr4Ni3O10
Yidian Li, Mingxin Zhang, Xian Du et al. (+22 more)
The interplay among orbital-selective Mott physics, Hund's coupling, tunable structural motifs, and Kondo-like scattering establishes a compelling paradigm for understanding and engineering correlated multi-orbital systems, as vividly exemplified by nickelate
superconductors. Here, using high-resolution angle-resolved photoemission spectroscopy combined with theoretical calculations, we systematically investigate the electronic properties of trilayer nickelates. In La4Ni3O10, we observe pronounced interorbital hybridization, whereas in Pr4Ni3O10, the flat d_(z^2 ) band becomes markedly incoherent and diminishes in spectral weight. By contrast, the dispersive d_(x^2-y^2 ) bands retain coherence in both compounds. This striking incoherence/coherence dichotomy identifies an orbital-selective Mott phase modulated by the interlayer Ni-O-Ni bonding angle. The depletion of the d_(z^2 ) orbitals further frustrates the interorbital hybridization and influences the density-wave transition in Pr4Ni3O10. Moreover, the density-wave gap is substantially reduced in Pr4Ni3O10, likely due to extra scattering channels provided by the local moments of Pr3+ cations. Our findings elucidate the intricate interplay among
lattice, orbital,
spin, and electronic degrees of freedom and reveal a feasible structural control parameter for the multi-orbital correlated state in trilayer nickelates, which provide a concrete framework for understanding the emergence of superconductivity under high pressure.
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All authors Yidian Li, Mingxin Zhang, Xian Du, Cuiying Pei, Jieyi Liu, Houke Chen, Wenxuan Zhao, Kaiyi Zhai, Yinqi Hu, Senyao Zhang, Jiawei Shao, Mingxin Mao, Yantao Cao, Jinkui Zhao, Zhengtai Li, Dawei Shen, Yaobo Huang, Makoto Hashimoto, Donghui Lu, Zhongkai Liu, Yulin Chen, Hanjie Guo, Yilin Wang, Yanpeng Qi, Lexian Yang
Strongly Correlated Electrons
Resolving Quantum Criticality in the Honeycomb Hubbard Model
Fo-Hong Wang, Fanjie Sun, Chenghao He et al. (+1 more)
Quantum phase transitions driven by electronic correlations are central to understanding the physics of
graphene and related two-dimensional materials. A paradigmatic example is the semimetal-to-Mott-
insulator transition on the honeycomb
lattice, governed by the Gross-Neveu-Heisenberg universality class, yet consensus on its critical exponents has remained elusive for over a decade due to severe finite-size effects and the absence of rigorous conformal bootstrap
benchmarks. Here we try to resolve this long-standing controversy by performing projector determinant
quantum Monte Carlo simulations on
lattices of unprecedented size, reaching 10,368 sites. By developing a novel projected submatrix update
algorithm, we achieve a significant algorithmic speedup that enables us to access the thermodynamic limit with high precision. We observe that the
fermion anomalous dimension and the correlation length exponent converge rapidly, while the
boson anomalous dimension exhibits a systematic size dependence that we resolve via linear extrapolation. To validate our analysis, we perform parallel large-scale simulations of the spinless $t$-$V$ model on the honeycomb
lattice, which belongs to the Gross-Neveu-Ising class. Our results for the $t$-$V$ model show agreement with conformal bootstrap predictions, thereby corroborating the robustness of our methodology. Our work provides state-of-the-art critical exponents for the honeycomb Hubbard model and establishes a systematic finite-size scaling workflow applicable to a broad class of strongly correlated
quantum systems, paving the way for resolving other challenging fermionic
quantum critical phenomena.
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All authors Fo-Hong Wang, Fanjie Sun, Chenghao He, Xiao Yan Xu
Materials Science
Ab initio Phase Diagram of Ta2O5
Yan Gong, Huimin Tang, Yong Yang et al. (+1 more)
Tantalum pentoxide (Ta2O5) is a polymorphic wide-bandgap
semiconductor with outstanding dielectric properties and widespread use in optical and electronic technologies. Its rich structural diversity, arising from multiple polymorphs accessible under different synthesis conditions, has made Ta2O5 a long-standing subject of interest. However, a unified understanding of the thermodynamic stability and phase transitions of its polymorphs across pressure-temperature (P-T) space has remained elusive. Here, using first-principles calculations, we map the thermodynamic landscape of Ta2O5 and establish a comprehensive P-T phase diagram together with a phase-stability hierarchy. We find that Gamma-Ta2O5 and B-Ta2O5 dominate the phase diagram over a broad range of P-T conditions: Gamma-Ta2O5 is stabilized at low pressures, while B-Ta2O5 becomes thermodynamically favored at higher pressures up to ~ 60 GPa, beyond which Y-Ta2O5 emerges as the most stable phase. Crucially, the zero-point energy (ZPE), one aspect of
nuclear quantum effects (NQEs), plays a significant role in determining relative phase stability, contributing substantially to the Gibbs free energy and altering phase boundaries. A re-entrant phase transition between Gamma and B-Ta2O5 is predicted near ~ 2 GPa, revealing unexpected complexity in the phase behavior of this
oxide. More generally, we identify a characteristic temperature (T_0), at which zero-point and thermal
phonon contributions to the free energy become comparable, and show that T_0 is approximately one-third of the Debye temperature. This relationship provides a simple, physically transparent criterion for assessing the importance of NQEs in phase stability, with implications extending beyond Ta2O5 to a broad class of complex
oxides.
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All authors Yan Gong, Huimin Tang, Yong Yang, Yoshiyuki Kawazoe
Mesoscale and Nanoscale Physics
Probing quantum geometric nonlinear magnetization via second-harmonic magneto-optical Kerr effect
Xuan Qian, Xiao-Bin Qiang, Wenkai Zhu et al. (+5 more)
Quantum geometry provides an intrinsic framework for characterizing the
geometric structure of
quantum states. It highlights its relevance to various aspects of fundamental physics. However, its direct implications for
magnetic phenomena remain largely unexplored. Here, we report the observation of electric-field-induced nonlinear magnetization in the nonmagnetic semimetal WTe$_2$ by using a second-harmonic magneto-optical Kerr effect (SMOKE) spectroscopy. We observe a robust nonlinear SMOKE signal that scales quadratically with current and persists up to 200 K. Theoretical modeling and scaling analysis indicate that this nonlinear magnetization is dominated by the orbital contribution and is intrinsically linked to the
quantum Christoffel symbol. Just as the Christoffel symbol is a fundamental quantity encoding spacetime geometry in Einstein's general relativity, our work establishes a direct link between
quantum geometry and nonlinear magnetization, and provides a
geometric perspective for designing future orbitronic devices.
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All authors Xuan Qian, Xiao-Bin Qiang, Wenkai Zhu, Yuqing Huang, Yiyuan Chen, Hai-Zhou Lu, Yang Ji, Kaiyou Wang