Quantum Gases
A Nonequilibrium Equation of State for a Turbulent 2D Bose Gas
Yi Jiang, Nikolai Maslov, Andrey Karailiev et al. (+3 more)
Nonequilibrium equations of state can provide an effective thermodynamic-like description of far-from-
equilibrium systems. We experimentally construct such an equation for a direct energy cascade in a turbulent two-dimensional Bose gas. Our homogeneous gas is continuously driven on a large length scale and, with matching dissipation on a small length scale, exhibits a nonthermal but stationary power-law momentum distribution. Our equation of state links the cascade amplitude with the underlying scale-invariant energy flux, and can, for different drive strengths, gas densities, and interaction strengths, be recast into a universal power-law form using scalings consistent with the Gross-Pitaevskii model.
Read the full abstract ▾
All authors Yi Jiang, Nikolai Maslov, Andrey Karailiev, Christoph Eigen, Martin Gazo, Zoran Hadzibabic
Quantum Gases · Cross-listed from quant-ph
U(1) lattice gauge theory and string roughening on a triangular Rydberg array
Lisa Bombieri, Torsten V. Zache, Hannes Pichler et al. (+1 more)
Lattice gauge theories (LGTs) describe fundamental interactions in particle physics. A central phenomenon in these theories is confinement, which binds
quarks and antiquarks into
hadrons through the formation of string-like flux tubes of gauge fields. Simulating confinement dynamics is a challenging task, but recent advances in
quantum simulation are enabling the exploration of LGTs in regimes beyond the reach of classical computation. For analog devices, a major difficulty is the realization of strong plaquette interactions, which generate string fluctuations that can drive a roughening transition. Understanding string roughening – where strong transversal functions lead to an effective restoration of translational
symmetry at long distances – is of central importance in the study of confinement. In this work, we show that string roughening emerges naturally in an analog Rydberg
quantum simulator. We first map a triangular Rydberg array onto a (2+1)D U(1) LGT where plaquette terms appear as first-order processes. We study flux strings connecting static charges and demonstrate that, near a deconfined
quantum critical point, the string exhibits logarithmic growth of its transverse width as the separation between charges increases, along with the universal Lüscher correction to the confining potential – both signatures of string roughening. Finally, we investigate the real-time dynamics of an initially rigid string, observing large fluctuations after quenching into the roughening regime, as well as string breaking via particle-pair creation. Our results indicate that rough strings can be realized in experimentally accessible
quantum simulators, opening the door to detailed studies of how strong fluctuations influence string-breaking dynamics.
Read the full abstract ▾
All authors Lisa Bombieri, Torsten V. Zache, Hannes Pichler, Daniel González-Cuadra
Mesoscale and Nanoscale Physics
Quasi-flat and exact flat bands in patterned two-dimensional electron gases and honeycomb wire networks
Chunxiao Liu, Igor Pishniak, Benoît Douçot et al. (+1 more)
We investigate the formation of flat bands in a two-dimensional electron gas patterned by a periodic triangular array of repulsive antidots. In the high-barrier, narrow-trench regime, the spectrum develops kagome-like band triplets, each comprising a nearly flat band and two dispersive bands, with wave functions concentrated along the potential-free trenches. The two lowest energy bands have a different character with
graphene-like dispersion and wave functions localized near the junction centers. The appearance of the trench-concentrated nearly flat bands further motivates a honeycomb
quantum graph model as an effective description of the narrow-trench limit. In the single-channel graph, destructive interference produces exact flat bands with compact localized eigenstates protected by the $D_3$
symmetry. Their energies obey a quantization condition determined by propagation along the links and scattering at the junctions. We then extend the analysis to a multichannel
quantum graph and derive the most general junction scattering
matrix compatible with $D_3$
symmetry. Even- and odd-parity transverse channels contain equivalent
symmetry sectors, and $D_3$
symmetry therefore allows them to mix. This mode conversion can disrupt the destructive interference responsible for flat bands and generically gives those bands a finite width. Exact flatness is nevertheless retained when only one transverse-parity sector is active, or when an additional
symmetry forbids mixing between the two sectors. These results connect the continuum antidot model to its
quantum-graph limit and identify transverse-mode mixing as a mechanism that limits flatness in multichannel networks.
Read the full abstract ▾
All authors Chunxiao Liu, Igor Pishniak, Benoît Douçot, Jérôme Cayssol
Quantum Gases · Cross-listed from quant-ph
Quantum-controlled synthetic materials
Andrei Vrajitoarea, Gabrielle Roberts, Kaden R. A. Hazzard et al. (+2 more)
Analog
quantum simulators and digital
quantum computers are two distinct paradigms driving near-term applications in modern
quantum science, from probing many-body phenomena to identifying computational advantage over classical systems. A transformative opportunity on the horizon is merging the high-fidelity many-body
evolution in analog simulators with the robust control and measurement of digital machines. Such a hybrid platform would unlock new capabilities in state preparation, characterization and dynamical control. Here, we embed digital
quantum control in the analog
evolution of a synthetic
quantum material by entangling the
lattice potential landscape of a Bose-Hubbard
circuit with an ancilla
qubit. This
Hamiltonian-level control induces dynamics under a superposition of different
lattice configurations and guides the many-body system to novel strongly-correlated states where different phases of matter coexist – ordering
photons into superpositions of solid and fluid eigenstates. Leveraging hybrid control modalities, we adiabatically introduce disorder to localize the
photons into an entangled cat state and enhance its coherence using a many-body echo technique. This work illustrates the potential for entangling
quantum computers with
quantum matter – synthetic and solid-state – for advantage in sensing and materials characterization.
Read the full abstract ▾
All authors Andrei Vrajitoarea, Gabrielle Roberts, Kaden R. A. Hazzard, Jonathan Simon, David I. Schuster
Materials Science
Novel non-thermal Ablation Mechanics in the Laser Ablation of Silicon
Dominic Klein, Simon Kümmel and Johannes Roth
We investigate the non-thermal material dynamics of strongly excited silicon during ultra-fast
laser ablation. In contrast to metals, silicon shows strongly excitation-dependent interatomic bonding strengths, which gives rise to a number of unique material dynamics like non-thermal melting, Coulomb explosions and altered carrier heat conduction due to charge carrier confinement. In this study, we report novel non-thermal ablation mechanisms in the ultra-fast single shot
laser ablation of silicon and perform large scale massive multi-parallel simulations on experimentally achievable length scales with atomistic resolution. For this, we model the ultra-fast carrier dynamics utilizing the Thermal-Spike-Model coupled to Molecular Dynamics simulations and include the accompanied excitation-dependent nonthermal bonding strength manipulation by application of the excitation-dependent modified Tersoff Potential. Further, we present first results on the systematic construction of the excitation-dependent phase diagram of silicon by thermodynamic integration.
Read the full abstract ▾
Quantum Gases · Cross-listed from quant-ph
Dissipation stabilizes Dicke Time Quasicrystals
Sk Anisur, Shuva Mondal, Tanaya Ray et al. (+1 more)
Quasi-periodic driving protocols provide a powerful route to realize novel non-
equilibrium phases of matter beyond the Floquet paradigm. However, these protocols inevitably lead to infinite-temperature heat death in isolated systems, which poses a major challenge to their experimental realization. We demonstrate that dissipation can be harnessed to stabilize quasi-periodically driven systems, enabling the realization of robust non-
equilibrium phases. Using the paradigmatic open Dicke model, we provide a blueprint for realizing a stable time quasicrystal (TQC) by Fibonacci driving. This TQC is characterized by a robust sub-harmonic quasi-periodic response that is dictated by, but qualitatively distinct from the external Fibonacci drive. By directly analyzing the time
evolution in the thermodynamic limit, we establish the existence of TQC order in this system for a wide parameter regime. We trace the origin of the stability of the TQC to the attractor structure induced by dissipation. Strikingly, the TQC order persists in the deep
quantum regime with as few as two
qubits. We systematically study the dependence of the TQC lifetime, $\tau^{\ast}$, on the number of
qubits and demonstrate that $\tau^{\ast}$ increases monotonically with the system size. Crucially, the TQC is not observed in the absence of dissipation. Our work establishes dissipation as a mechanism for stabilizing non-
equilibrium phases of matter under quasi-periodic drive.
Read the full abstract ▾
All authors Sk Anisur, Shuva Mondal, Tanaya Ray, Sayan Choudhury
Soft Condensed Matter
Broadening the temperature range of blue phases using $azo$ compounds of various molecular geometries assembled from modular "LEGO" molecular units
Igor A. Gvozdovskyy, Vitalii O. Chornous, Halyna V. Bogatyryova et al. (+5 more)
The temperature range of the blue phases (BPs) formed in highly
chiral mixtures based on cholesteryl oleyl carbonate (COC) and the nematic
liquid crystal E7 was studied in the presence of various chemical structures. The $azo$ compounds used were of both
chiral and achiral nature, and their molecular geometry was modified by substitution of modular "LEGO" molecular units of varying alkyl chain lengths and types of bridging groups, which could substantially affect the mesomorphic properties of the
matrix mixture. It was shown that in many cases these dopants effectively broadened the BP temperature range. This effect depends on both the variation in the molecular geometry of the $azo$ compounds and the increase in the $cis$-isomer concentration under UV irradiation. The presence of the $cis$-isomers formed have a stronger impact on broadening the BP temperature range than the initial $trans$-isomers. These results demonstrate that the temperature range of BPs can be precisely controlled via a combination of molecular engineering and $trans$-$cis$ photo-isomerization.
Read the full abstract ▾
All authors Igor A. Gvozdovskyy, Vitalii O. Chornous, Halyna V. Bogatyryova, Oleksandr M. Samoilov, Longin N. Lisetski, Serhiy V. Ryabukhin, Yurii V. Dmytriv, Mykhaylo V. Vovk
Quantum Gases · Cross-listed from physics.atom-ph
Extended Rydberg Lifetimes in a Cryogenic Atom Array
Junlan Jin, Yue Shi, Youssef Aziz Alaoui et al. (+4 more)
We report on the realization of a $^{133}$Cs optical tweezer array in a cryogenic blackbody radiation (BBR) environment. By enclosing the array within a 4K radiation shield, we measure long Rydberg lifetimes, up to $406 (36)\,\mu$s for the $55 P_{3/2}$ Rydberg state, a factor of 3.3(3) longer than the room-temperature value. We employ single-
photon coupling for coherent manipulation of the ground-Rydberg
qubit. We measure a small differential dynamic polarizability of the transition, beneficial for reducing dephasing due to light intensity fluctuations. Our results pave the path for advancing neutral-atom two-
qubit gate fidelities as their error budgets become increasingly dominated by $T_1$ relaxation of the ground-Rydberg
qubit.
Read the full abstract ▾
All authors Junlan Jin, Yue Shi, Youssef Aziz Alaoui, Jingxin Deng, Yukai Lu, Jeff D. Thompson, Waseem S. Bakr
Soft Condensed Matter
Geometry and dynamical morphology of growing bacterial colonies
Benjamin Evert Himberg and Sanghita Sengupta
We study non-
equilibrium bacterial colony growth using a geometry-first, time-resolved analysis of morphology. From time-lapse microscopy data, we track the coupled
evolution of area, perimeter, and boundary-sensitive shape descriptors along the full growth history. We find that non-
equilibrium growth can exhibit extended intervals of compact area–perimeter scaling with exponent $\alpha \approx 2$, consistent with growth governed by a single effective
geometric length scale, as well as time-localized breakdowns of this scaling during ongoing growth. These breakdowns coincide with transient boundary reorganization while bulk area growth remains sustained. Our results demonstrate that visually distinct morphologies can arise within the same
geometric growth regime, and that departures from single-scale behavior reflect intrinsic dynamical restructuring rather than growth arrest. More broadly, this work establishes time-resolved geometry as a coarse-grained framework for identifying when non-
equilibrium growth departs from single-scale
geometric constraints in living systems.
Read the full abstract ▾
Quantum Gases
An Approach to Probing Particles and Quasi-particles in the Condensed Bose-Hubbard Model
Huy Nguyen, Yu-Xin Wang and Jacob M. Taylor
Measurement plays a crucial role in a
quantum system beyond just learning about the system state: it changes the post-measurement state and hence influences the subsequent time
evolution; further, measurement can even create
entanglement in the post-measurement conditional state. In this work, we study how careful choice of parameters for a typical measurement process on cold atoms systems – phase contrast imaging – has a strong impact on both what the experimentalist observes but also on the backaction the measurement has on the system, including the creation and
diffusion of quasiparticles emerging from the
quantum many-body dynamics. We focus on the case of a Bose-Einstein-condensate array, in the low-temperature and low-momentum limit. Our theoretical investigation reveals regimes where the imaging light probes either the bare particle or quasiparticle dynamics. Moreover, we find a path to selectively measuring quasiparticle modes directly, as well as controlling over the measurement-induced creation and
diffusion of quasiparticles into different momentum states. This lays a foundation for understanding the effects of both experimental approaches for probing many-body systems, but also more speculative directions such as observable consequences of `spontaneous collapse' predictions from novel models of
quantum gravity on aspects of the Standard Model.
Read the full abstract ▾
Materials Science
Platform and Framework for Time-Resolved Nanoscale Thermal Transport Measurements in STEM
Mairi McCauley, Joel Martis, Ondrej L. Krivanek et al. (+12 more)
Understanding heat transport at the nanometer scale is critical for
semiconductor devices,
quantum materials, and thermal management of nanostructures, yet direct local measurements of thermal conductivity and heat capacity remain scarce. We developed a
laser-excitation system integrated into a scanning transmission electron microscope (STEM) for nanoscale thermal transport measurements using ultra-high-resolution electron energy-loss spectroscopy (EELS). A fiber-coupled
laser is introduced via a modified aperture mechanism, enabling flexible holder geometries and large tilt angles without optical elements in the polepiece gap. Synchronization of pulsed
laser excitation with an externally gated direct electron detector provides temporal resolution about 50 ns at <10 meV energy resolution. Local temperatures are determined via the principle of detailed balance, and thermal transport parameters are extracted by fitting a forward-time central-space heat
diffusion model including radiative losses. For amorphous carbon films, we obtain a thermal conductivity of 1.24 $\frac{W}{m\cdot K}$ and a heat capacity of 821 $\frac{J}{kg\cdot K}$, consistent with literature. This framework enables time-resolved nanoscale measurements of thermal transport in materials and devices.
Read the full abstract ▾
All authors Mairi McCauley, Joel Martis, Ondrej L. Krivanek, Ben Plotkin-Swing, Andreas Mittelberger, Tolga Wagner, Hüseyin Çelik, Grigory Kornilov, Meng Zhao, Matthias Meffert, Luca Piazza, Tracy C. Lovejoy, Guillaume Radtke, Christoph Koch, Benedikt Haas
Strongly Correlated Electrons
Spontaneous Parity Breaking in Quantum Antiferromagnets on the Triangular Lattice
Songtai Lv, Yuchen Meng and Haiyuan Zou
Frustration on the triangular
lattice has long been a source of intriguing and often debated phases in many-body systems. Although
symmetry analysis has been employed, the role of the seemingly trivial parity
symmetry has received little
attention. In the work described in this Letter, we show that phases induced by frustration are systematically shaped by an implicit rule of thumb associated with spontaneous parity breaking in weak longitudinal field. This principle enables us to anticipate and rationalize the regimes and conditions under which nontrivial phases emerge. For the
spin-$S$
antiferromagnetic XXZ model, we demonstrate that a controversial parity-broken phase appears at intermediate values of $S$. In
bilayer systems, enhanced frustration leads to additional phases, such as supersolids, whose properties can be classified by their characteristic parity features. Benefiting from our improved tensor network contraction techniques, we confirm these results through large-scale tensor-network calculations. This study offers an alternative viewpoint and a systematic approach for examining the interplay between
spin,
symmetry, and frustration in many-body systems.
Read the full abstract ▾
Strongly Correlated Electrons
Reducing the Computational Cost Scaling of Tensor Network Algorithms via Field-Programmable Gate Array Parallelism
Songtai Lv, Yang Liang, Rui Zhu et al. (+2 more)
Improving the computational efficiency of
quantum many-body calculations from a hardware perspective remains a critical challenge. Although field-programmable gate arrays (FPGAs) have recently been exploited to improve the computational scaling of
algorithms such as Monte Carlo methods, their application to tensor network
algorithms is still at an early stage. In this work, we propose a fine-grained parallel tensor network design based on FPGAs to substantially enhance the computational efficiency of two representative tensor network
algorithms: the infinite time-evolving block decimation (iTEBD) and the higher-order tensor renormalization group (HOTRG). By employing a quad-tile partitioning strategy to decompose tensor elements and map them onto hardware
circuits, our approach effectively translates algorithmic computational complexity into scalable hardware resource utilization, enabling an extremely high degree of parallelism on FPGAs. Compared with conventional CPU-based implementations, our scheme exhibits superior scalability in computation time, reducing the bond-dimension scaling of the computational cost from $O(D_b^3)$ to $O(D_b)$ for iTEBD and from $O(D_b^6)$ to $O(D_b^2)$ for HOTRG. This work provides a theoretical foundation for future hardware implementations of large-scale tensor network computations.
Read the full abstract ▾
All authors Songtai Lv, Yang Liang, Rui Zhu, Qibin Zheng, Haiyuan Zou
Strongly Correlated Electrons
Giant bubbles of Fisher zeros in the quantum XY chain
Songtai Lv, Yang Liu, Erhai Zhao et al. (+2 more)
We demonstrate an alternative approach based on a complex-valued inverse temperature and partition function to probe
quantum phases of matter with nontrivial spectra and dynamics. It leverages thermofield dynamics (TFD) to quantitatively characterize
quantum and thermal fluctuations, and exploit the correspondence between low-energy excitations and Fisher zeros. Using the
quantum XY chain in an external field as a testbed, we show that the oscillatory gap behavior manifests as oscillations in the long-time dynamics of the TFD spectral form factor. We also identify
giant bubbles, i.e. large-scale closed lines, of Fisher zeros near the gapless XX limit. They provide a characteristic energy scale that seems to contradict the predictions of the low energy theory of a featureless Luttinger
liquid. We identify this energy scale and relate the motion of these
giant bubbles with varying external field to the transfer of spectral weight from high to low energies. The deep connection between Fisher zeros, dynamics, and excitations opens up promising avenues for understanding the unconventional gap behaviors in strongly correlated many-body systems.
Read the full abstract ▾
All authors Songtai Lv, Yang Liu, Erhai Zhao, Haiyuan Zou, Tao Xiang
Strongly Correlated Electrons
Topological piezomagnetic effect in two-dimensional Dirac quadrupole altermagnets
H. Radhakrishnan, B. Bell, C. Ortix et al. (+1 more)
Altermagnets provide a natural platform for studying and exploiting piezomagnetism. In this paper, we introduce a class of insulating altermagnets in two dimensions (2D) referred to as Dirac quadrupole altermagnets, and show based on microscopic minimal models that the orbital piezomagnetic polarizability of such altermagnets has a topological contribution described by topological response theory. The essential low-energy electronic structure of Dirac quadrupole altermagnets can be understood from a gapless parent phase (i.e., the Dirac quadrupole semimetal), which has important implications for their response to external fields. Focusing on the strain-induced response, here we demonstrate that the topological piezomagnetic effect is a consequence of the way in which strain affects the Dirac points forming a quadrupole. We consider two microscopic models: a spinless two-band model describing a band inversion of $s$ and $d$ states, and a Lieb
lattice model with collinear Néel order. The latter is a prototypical minimal model for altermagnetism in 2D and is realized in a number of recently proposed material compounds, which are discussed.
Read the full abstract ▾
All authors H. Radhakrishnan, B. Bell, C. Ortix, J. W. F. Venderbos
Materials Science
Low-temperature spin dynamics in LAFO thin films: from cubic anisotropy to TLS-limited coherence
Srishti Pal, Guanxiong Qu, Hervé M. Carruzzo et al. (+6 more)
We investigate the low-temperature
spin dynamics of epitaxial lithium aluminum ferrite (LAFO) thin films using broadband
ferromagnetic resonance (FMR) spectroscopy from 0.44 K to 68 K. The results reveal a crossover from conventional cubic anisotropy-dominated behavior at higher temperatures to pronounced linewidth broadening and higher-order anisotropy contributions at cryogenic temperatures. With the
magnetic field oriented along the [100] crystallographic direction, the resonance is well-captured by four-fold in-plane and out-of-plane uniaxial anisotropies. In contrast, measurements with the field along the [110] direction reveal the presence of an unusually large sixth-order cubic anisotropy term that is
symmetry-suppressed for [100] but becomes apparent under this field orientation at ultralow temperatures, indicating a substantial modification of the anisotropy landscape. Independent linewidth analysis shows a pronounced peak near 8 K and a subtle monotonic enhancement with decreasing temperatures below 2 K, features consistent with dissipation mediated by a bath of two-level systems (TLS) arising from antisite defects and localized Fe$^{3+}$ moments. Comparison with TLS-based models demonstrates that both exchange-coupled
impurities and nearly free paramagnetic centers contribute to the observed damping. Our results establish LAFO as a model ferrite system where disorder-induced TLS limit
spin coherence at ultralow temperatures, providing new insights into anisotropy engineering,
magnetic relaxation, and the design of ferrimagnetic
insulators for coherent magnonics. These findings offer a framework for future optimization of growth conditions.
Read the full abstract ▾
All authors Srishti Pal, Guanxiong Qu, Hervé M. Carruzzo, Katya Mikhailova, Lerato Takana, Qin Xu, Yuri Suzuki, Clare C. Yu, Gregory D. Fuchs
Materials Science
AMDAT: An Open-Source Molecular Dynamics Analysis Toolkit for Supercooled Liquids, Glass-Forming Materials, and Complex Fluids
Pierre Kawak, William F. Drayer, Bao Khanh Ma et al. (+1 more)
AMDAT (Amorphous Molecular Dynamics Analysis Toolkit) is an open-source C++ toolkit for post-processing molecular dynamics trajectories, focused on high-performance static and dynamic analyses of amorphous, glassy, and
polymer materials, including supercooled
liquids and complex fluids. In this paper, we describe AMDAT's design for efficient long-timescale analysis via in-
memory trajectory handling and exponential time sampling, and we demonstrate representative workflows for widely used observables such as radial distribution functions, structure factors, intermediate scattering functions, and neighbor correlations.
Read the full abstract ▾
All authors Pierre Kawak, William F. Drayer, Bao Khanh Ma, David S. Simmons
Disordered Systems and Neural Networks
Weak- and strong-disorder effects in the continuous random-field Ising model
G. O. Heymans, N. F. Svaiter, B. F. Svaiter et al. (+1 more)
We discuss the weak- and strong-disorder effects in the continuous random-field Ising model using the distributional
zeta-function method. In the weak-disorder regime, the
vacuum is located at the origin, whereas in the strong-disorder regime, the
vacuum is shifted from the origin. By performing the quenched-disorder average at the level of the effective action, we derive the quadratic and interaction terms. In the weak-disorder limit, we show that the infrared structure of the two-point correlation functions yields a decomposition of the physical field into correlated components with distinct scaling dimensions. This mechanism exhibits the characteristic $1/p^4$ behavior, which shifts the upper critical dimension to $d_c^{+}=6$. The universal critical behavior of the RFIM near this dimension is governed by a minimal infrared effective action. In the strong-disorder regime, we obtain a diagonal quadratic action with a discrete spectrum of massive modes. The absence of massless modes implies that conventional criticality may be replaced by a
symmetry-restoration transition. The resulting spectral representation of correlation functions converges rapidly and remains well controlled in the infrared limit.
Read the full abstract ▾
All authors G. O. Heymans, N. F. Svaiter, B. F. Svaiter, A. M. S. Macêdo
Statistical Mechanics · Cross-listed from quant-ph
Quantum statistical functions
Haruki Emori
Statistical functions such as the moment-generating, characteristic, cumulant-generating, and second characteristic functions are standard tools in classical statistics and probability theory. They provide a systematic means to analyze the statistical properties of a system and find applications in diverse fields. While these functions are ubiquitous in classical theory, a
quantum counterpart has remained underdeveloped because of the noncommutativity of operators. The absence of such a framework has obscured the connections between statistical quantities and the nonclassical features of
quantum mechanics. Here, we construct a framework for
quantum statistical functions that addresses these limitations and unifies the
languages of
quantum statistics. We show that the functions reproduce standard statistical quantities such as expectation values, variance, and covariance upon differentiation. By extending the framework to include pre- and post-selection, we define conditional functions that generate conditional statistical quantities, including the weak value and the weak variance. We further show that multivariable functions, defined with specific operator orderings, correspond to the Kirkwood–Dirac, Margenau–Hill, and Wigner distributions. By generalizing Bochner's
theorem within the theory of compactly supported distributions, we obtain a criterion that separates classical statistics from
quantum statistics, linking the failure of positive definiteness of the multivariable function to the emergence of quasiprobability. As an application, we import the classical method of moments and generalized method of moments into
quantum estimation, introducing
quantum estimators that exploit the proposed functions. Our framework reproduces
quantum statistical quantities and incorporates the nonclassical features of quasiprobability, providing a basis for further study of
quantum statistics.
Read the full abstract ▾
Strongly Correlated Electrons
Suppressed coarsening after an interaction quench in the Holstein chain
Ho Jang and Gia-Wei Chern
We investigate the nonequilibrium dynamics induced by an interaction quench in the semiclassical Holstein model within the Ehrenfest nonadiabatic framework, which describes an isolated hybrid
quantum-classical system with strictly conserved total energy. Focusing on the half-filled case, where the
equilibrium ground state exhibits commensurate charge-density-wave (CDW) order for any nonzero coupling, we identify three distinct post-quench dynamical regimes as a function of the final electron-
phonon coupling: a nonequilibrium metallic state without CDW order, an intermediate regime characterized by slow scale-invariant ordering dynamics, and a frozen CDW state with arrested coarsening and immobile kinks. We analyze the intermediate regime in detail and uncover an unconventional algebraic decay of the kink density, $n \sim t^{-1/3}$, distinct from both ballistic annihilation and diffusive coarsening in classical dissipative systems. We show that this anomalous exponent arises from the hybrid nature of the dynamics: while the
lattice evolves deterministically, the electronic degrees of freedom act as an effective internal bath that induces diffusive kink motion without energy dissipation. An effective reaction-
diffusion description, incorporating both annihilation and elastic scattering of kinks, quantitatively accounts for the observed scaling behavior. Our results reveal a distinct coarsening mechanism in isolated hybrid systems, demonstrating how internal
quantum dynamics can qualitatively reshape defect kinetics far from
equilibrium.
Read the full abstract ▾
Soft Condensed Matter
Vortex formation in the Vicsek model with internal chirality of self-propelling objects
W. T. Gozdz and A. Ciach
Effect of internal chirality on collective motion of a large number of active objects is studied by simulations of appropriately modified Vicsek model. We add a fixed angle to the noise and consider small ratios, $p$, between this angle and the maximal deviation from the average local direction of motion. When the above ratio is $p=1/120$, the traveling bands observed with the symmetrical noise are destroyed, and small bands moving in different directions appear. Circular rotating flocks of objects with the same orientation are formed for $p=1/7.5$. Stable vortexes in the stationary state were found from $p=1/60$ to $p=1/20$. Velocity autocorrelation function shows
equilibrium between the inflow and the
outflow to and from the
vortex. Long-time
evolution is considerably influenced by a temporary trapping of the objects in the
vortex. The ballistic behavior for the symmetrical noise changes to the diffusive behavior for the chirality leading to the onset of vortexes.
Read the full abstract ▾
Superconductivity
Fit-Free Optical Determination of Electronic Thermalization Time in Nematic Iron-Based Superconductors
Alexander Bartenev, Roman Kolodka, Ki-Tae Eom et al. (+6 more)
We present a nematic response function model (NRFM) for fit-free direct extraction of the characteristic time of ultrafast electronic thermalization in iron-based
superconductors, materials with electronic nematicity. By combining the NRFM for polarization-dependent pump–probe measurements of electronic nematic response with the two-temperature model (TTM) for sub-picosecond quasiparticle relaxation, we quantify the electronic thermalization timescales and their anisotropy. The nematic response function is modeled as the difference of normalized reflectivity signals, revealing a pronounced sub-picosecond extremum in signal
evolution that directly yields the characteristic electronic thermalization time. This method demonstrates that the NRFM is consistent with TTM fits of transient optical response, yielding electronic thermalization time constants on the order of 110–230~fs for the FeSe$_{1-x}$Te$_x$ and Ba(Fe$_{0.92}$Co$_{0.08}$)$_2$As$_2$ thin films. The proposed approach can be applied to any material that exhibits electronic nematicity, providing a powerful tool for direct mapping of the relaxation time in nematic materials, avoiding complex experimental data-fitting procedures.
Read the full abstract ▾
All authors Alexander Bartenev, Roman Kolodka, Ki-Tae Eom, Jong-Hoon Kang, Adrian Rua-Melendez, Jason Kawasaki, Chang-Beom Eom, Armando Rua, Sergiy Lysenko
Soft Condensed Matter
Orthogonal Superposition Rheometry of soft core-shell microgels
Panagiota Bogri, Gabriele Pagani, Jan Vermant et al. (+2 more)
The mechanisms of flow in suspensions of soft particles above the glass-transition volume fraction and in the jammed state were probed using Orthogonal Superposition Rheometry (OSR). A small amplitude oscillatory shear flow is superimposed orthogonally onto a steady shear flow, which allows monitoring the viscoelastic spectra of sheared jammed core-shell microgels during flow. The characteristic crossover frequency {\omega}c, deduced from the viscoelastic spectrum, provides information about the shear induced structural relaxation time, which is connected to the microscopic yielding mechanism of cage breaking. The shear rate
evolution of the crossover frequency is used to achieve a superposition of all spectra and get a better insight of the flow mechanism. Despite their inherent softness, the hybrid core-shell microgels exhibit similarities with hard sphere-like flow behavior, with the main difference that for the microgels the transition from a glassy to a jammed state introduces a volume fraction dependence of the scaling of {\omega}c with shear rate. We further check the application of the Kramers-Kronig relations on the experimental low strain amplitude OSR data finding a good agreement. Finally, the low frequency response at high strain rates was investigated with open bottom
cell geometry and instrumental limits were identified. Based on these limits, we discuss previous OSR data and findings in repulsive and attractive colloidal glasses, and compared them with the current soft particle gels.
Read the full abstract ▾
All authors Panagiota Bogri, Gabriele Pagani, Jan Vermant, Joris Sprakel, George Petekidis
Mesoscale and Nanoscale Physics
Anomalous thermoelectric and thermal Hall effects in irradiated altermagnets
Fang Qin and Xiao-Bin Qiang
We show that a $d$-wave altermagnet can be transformed into a Chern
insulator by irradiating it with elliptically polarized light from a high-frequency
photon beam. We further explore the intrinsic anomalous thermoelectric and thermal
Hall effects in light-irradiated altermagnets. At low temperatures, the thermoelectric
Hall coefficient exhibits a linear temperature dependence but vanishes within the energy gap between the conduction and valence bands near the $M$ point. However, it displays pronounced peaks and dips at the gap boundaries near both the $M$ and $\Gamma$ points, suggesting that thermoelectric
Hall conductivity is a sensitive probe for these gapped regions. Similarly, the low-temperature thermal
Hall coefficient, which also shows a linear temperature dependence, becomes quantized across the bandwidth, reflecting the underlying topological character of the light-induced Chern insulating phase. These results establish thermoelectric and thermal
Hall transports as powerful signatures of
topology in driven altermagnetic systems.
Read the full abstract ▾
Materials Science
Questioning van der Waals Epitaxy of Non-Layered Materials on Mica: The Case of ScN
Susmita Chowdhury, Faezeh Alijan Farzad Lahiji, Mikael Ottoson et al. (+6 more)
Growing stress-free epitaxial films by van der Waals epitaxy (vdWE) is of interest for realizing flexible optoelectronics and energy devices from freestanding epilayers. However, vdWE of non-layered materials is often presumed or claimed on layered substrates such as mica with inadequate experimental evidence. Here, we demonstrate that the growth of single-domain rocksalt ScN(111) films by sputter deposition on fluorophlogopite mica(001) occurs by conventional epitaxy. X-ray diffraction and electron microscopy reveal the film/substrate epitaxial relationship to be [-101](111)ScN||[010](001)mica. Our results indicating strain buildup seen from the dependence of (111) interplanar spacings, and strain relaxation by dislocation generation, question prior claims of vdWE of non-layered metal nitrides on mica. Our findings show that conventional epitaxy should be the default assumption for non-layered materials unless conditions for vdWE are explicitly established.
Read the full abstract ▾
All authors Susmita Chowdhury, Faezeh Alijan Farzad Lahiji, Mikael Ottoson, Olivier Donzel-Gargand, Robert J. W. Frost, Martin Magnuson, Ganpati Ramanath, Arnaud le Febvrier, Per Eklund
Mesoscale and Nanoscale Physics
Color Centers and Hyperbolic Phonon Polaritons in Hexagonal Boron Nitride: A New Platform for Quantum Optics
Jie-Cheng Feng, Johannes Eberle, Sambuddha Chattopadhyay et al. (+3 more)
Hyperbolic phonon polaritons (HPPs) in hexagonal boron nitride (hBN) confine mid-infrared light to deep-subwavelength scales and may offer a powerful route to strong light-matter interactions. Generation and control of HPPs are typically accessed using classical near-field probes, which limits experiments at the
quantum level.A complementary frontier in hBN research focuses on color centers: bright, stable, atomically localized emitters that have rapidly emerged as a promising platform for solid-state
quantum optics. Here we establish a key connection between these two directions by developing a cavity-QED framework in which a single hBN color center serves as a
quantum source of HPPs. We quantify the emitter-HPP interaction and analyze two generation schemes. The first is spontaneous emission into the
phonon sideband, which can produce single-HPP events and, in ultrathin slabs, becomes single-mode with an enhanced decay rate. The second is a stimulated Raman process that provides frequency selectivity, tunable conversion rate, and narrowband excitation. This drive launches spatially confined, ray-like HPPs that propagate over micrometer distances. We also outline a two-emitter correlation measurement that can directly test the single-polariton character of these emissions. By connecting color-center
quantum optics with
hyperbolic polaritonics, our approach enables
quantum emitters to act as on-chip
quantum sources and controls for HPPs, while HPPs provide long-range channels that couple spatially separated emitters. Together, these capabilities point to a new direction for mid-infrared photonic experiments that unite strong coupling, spectral selectivity, and spatial reach within a single material system.
Read the full abstract ▾
All authors Jie-Cheng Feng, Johannes Eberle, Sambuddha Chattopadhyay, Johannes Knörzer, Eugene Demler, Ataç İmamoğlu
Materials Science
Broken neural scaling laws in materials science
Max Großmann, Malte Grunert and Erich Runge
In materials science, data are scarce and expensive to generate, whether computationally or experimentally. Therefore, it is crucial to identify how model performance scales with
dataset size and model capacity to distinguish between data- and model-limited regimes. Neural scaling laws provide a framework for quantifying this behavior and guide the design of materials
datasets and machine learning architectures. Here, we investigate neural scaling laws for a paradigmatic materials science task: predicting the dielectric function of metals, a high-dimensional response that governs how solids interact with light. Using over 200,000 dielectric functions from high-throughput ab initio calculations, we study two multi-objective graph neural networks trained to predict the frequency-dependent complex interband dielectric function and the Drude frequency. We observe broken neural scaling laws with respect to
dataset size, whereas scaling with the number of model parameters follows a simple power law that rapidly saturates.
Read the full abstract ▾
Soft Condensed Matter
Boundary compliance selects heterogeneous dynamics in shear-thickening suspensions
Li-Xin Shi, Meng-Fei Hu and Song-Chuan Zhao
The mechanical properties of confining boundaries can fundamentally alter the flow behaviour of shear-thickening suspensions. We study a dense cornstarch suspension sheared beneath a viscous silicone-oil layer, using the oil viscosity to tune boundary compliance. Flow visualisation and rheometry reveal two distinct regimes. With compliant boundaries, long-lived heterogeneities emerge via density waves or persistent clusters, maintained by a balance between interface deformation and particle rearrangement. With more resistant confinement, we observe transient jamming events, marked by abrupt spanning of load-bearing structures across the suspension thickness and the emergence of secondary stress waves. The onset stress of these events remains constant at the DST threshold, independent of bounding viscosity. Our results reveal that boundary compliance selects the lifetime and morphology of heterogeneous structures, offering a means to amplify otherwise short-lived microscopic processes and providing new insight into the interplay between shear thickening, shear jamming, and confinement mechanics.
Read the full abstract ▾
Strongly Correlated Electrons
Steady-state study of the nonequilibrium properties of SrVO$_3$
Tommaso Maria Mazzocchi, Markus Aichhorn and Enrico Arrigoni
We present the mixed-configuration approximation (MCA) based on the auxiliary master equation approach
impurity solver to study multiorbital correlated systems under
equilibrium and nonequilibrium conditions within dynamical mean-field theory (DMFT). We
benchmark the method for bulk and layered SrVO$_3$ in
equilibrium and apply it to a prototypical nonequilibrium geometry in which a voltage bias is applied perpendicular to the layer via reservoirs held at different chemical potentials. For bulk SrVO$_3$, MCA reproduces the metallic state at moderate interaction strengths, but it overestimates the weight of the lower band relative to
quantum Monte Carlo (QMC) and fork tensor product state (FTPS) solvers. With respect to QMC and FTPS, MCA yields an earlier metal-to-
insulator transition as the electron-electron interaction is increased. In layered SrVO$_3$ at
equilibrium, MCA partially captures the orbital polarization in favor of the in-plane $xy$ orbital, although not as strong as in the DMFT-converged results obtained with QMC. Finally, under applied bias, we observe a pronounced redistribution of orbital occupations, demonstrating that the method captures bias-driven orbital charge transfer in realistic materials in nonequilibrium conditions.
Read the full abstract ▾
Materials Science
Observation of large perpendicular magnetic anisotropy and excessive polar magneto-optical effect in Pt/CoFeB/Ru tri-layer system
Md Rejaul Karim, Aman Agrahari, Arun Singh Dev et al. (+7 more)
Heterostructures comprising ferromagnet (FM) and heavy metals (HM) with perpendicular
magnetic anisotropy (PMA) and interfacial Dzyaloshinskii-Moriya interaction (iDMI) can host
chiral domain walls and topological
spin textures, making them highly promising for various spintronics applications. In this paper, we have investigated the magneto-optical properties, the anomalous
Hall effect (AHE), and PMA of Pt/CoFeB/Ru multilayers engineered to possess significant iDMI. We utilized the Anomalous
Hall effect (AHE), and the polar magneto-optical Kerr effect (p-MOKE),
Hall response and the domain wall motion in Pt/CoFeB/Ru-systems. Both MOKE and AHE measurements confirm that the films maintain strong perpendicular magnetization for CoFeB thicknesses below 1.2 nm. The effective
magnetic anisotropy K_{\mathrm{eff}} of 0.88 \times 10^6 erg/cm^3 has been achieved without any post-annealing, highlighting the high-quality interface in this multilayer design. The angular dependence of the switching field deviates from the conventional Kondorsky model and is well described using a modified Kondorsky formalism, capturing the role of field-induced domain-wall softening and pinning effects in the reversal process. Furthermore, p-MOKE microscopy imaging during the magnetization reversal process provides detailed insight into domain nucleation and subsequent domain-wall propagation. The observations reveal well-defined, stable
magnetic domains that evolve coherently under the applied
magnetic field. Such a behavior is expected in the system where interfacial DMI, PMA interact to stabilize the
chiral Néel-type domain walls, which are essential for fast, low-power domain-wall motion driven by
spin-orbit torques.
Read the full abstract ▾
All authors Md Rejaul Karim, Aman Agrahari, Arun Singh Dev, Rakhul Raj, Mohd S Sabir, Arun Jacob Mathew, Joseph Vimal Vas, Yasuhiro Fukuma, V. Raghavendra Reddy, Rohit Medwal