Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Postselection-free ballistic-diffusive transition in monitored spin chains
K. G. S. H. Gunawardana, Ali G. Moghaddam and Teemu Ojanen
We study
spin and
entanglement dynamics in
spin-1/2 XXZ chains under periodic monitoring and show that this system exhibits two measurement-induced phase transitions: a steady-state
entanglement phase transition similar to those in monitored
quantum circuits and a ballistic-to-diffusive transition in transient dynamics. Specifically, we discover that at low monitoring rate, an initial configuration containing a domain wall $|\uparrow\uparrow\uparrow\ldots \downarrow\downarrow\downarrow\ldots\rangle$ spreads ballistically while, at large monitoring rates, the domain melting is diffusive. Extensive numerical simulations, supported by theoretical arguments, indicate that the ballistic-diffusive transition is intimately interlinked with the
entanglement phase transition. In contrast to the
entanglement phase transitions, which require exponentially complex postselection, the ballistic-diffusive transition can be observed without postselection and constitutes an experimentally accessible manifestation of the many-body Zeno effect.
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Other Condensed Matter
Phase-Topology Classification of Memristor Hysteresis Loops via Self-Crossings
Ovidiu-Zeno Lipan, Eric Neuhaus, Rafael Schio Wengenroth Silva et al. (+6 more)
Memristive devices have revolutionized non-volatile
memory and neuromorphic computing, yet the geometry of their hysteresis loops – in particular, the occurrence and robustness of multiple self-crossings – remains poorly understood. Here we introduce a topological and algebraic framework that treats the number of transverse self-intersections of a memristor hysteresis loop as a robust integer-valued invariant. Drawing on differential
topology, singularity theory, and cusp catastrophe, we employ discriminants and resultants to stratify the six-dimensional parameter space. This approach partitions the parameter space into structurally stable regions separated by explicitly computable catastrophe surfaces. We demonstrate that the crossing number remains strictly invariant under continuous deformations and changes only at self-tangencies or cusp singularities, thereby providing a complete classification of all multi-lobed hysteresis behaviors. These insights bridge device physics with modern singularity theory and suggest a clear roadmap for exploiting higher-order
memory effects in next-generation electronics and
brain-inspired hardware.
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All authors Ovidiu-Zeno Lipan, Eric Neuhaus, Rafael Schio Wengenroth Silva, Soumen Pradhan, Fabian Hartmann, Leonardo K. Castelano, Ana Luiza Costa Silva, Sven Höfling, Victor Lopez-Richard
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Autonomous oscillations in quantum electromechanics: tensor network treatment
Mahasweta Pandit, Sheikh Parvez Mandal, Mark T. Mitchison et al. (+1 more)
Transport-induced self-sustained oscillations in electromechanical systems convert a static electrochemical bias into robust, autonomous oscillatory motion in the absence of any external periodic drive. However, an exact description of such self-oscillations remains challenging in nanoscale electromechanical devices featuring a simultaneously large bosonic
Hilbert space, strong interactions, and structured fermionic leads. We formulate a tensor-network framework that combines a binary representation of the vibrational mode with mesoscopic reservoir
embeddings that enable controlled access to the self-oscillatory steady states and relevant transport observables without explicit real-time propagation. We demonstrate the emergence of mechanical self-oscillations across a broad set of operating conditions, in which strong electromechanical backaction, nonadiabatic oscillator dynamics, and energy-dependent electronic tunneling processes compete. Furthermore, we observe that for both slow and fast vibrating mechanical modes, suppressed vibrational occupation fluctuations in the self-oscillation window along the electromechanical coupling strength sweep are preceded by a peak in the occupation fluctuations. Collectively, we explore how both intrinsic system properties and environmental parameters govern such autonomous oscillations over a broad range of operating conditions. The broad applicability of our framework will facilitate further extension of the method to more complex and experimentally relevant scenarios to study the thermodynamics of
quantum autonomous devices with potential applications in
quantum sensing, timekeeping, information processing, and energy conversion.
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All authors Mahasweta Pandit, Sheikh Parvez Mandal, Mark T. Mitchison, Javier Prior
Materials Science
Microstructure-Aware Deep Learning Bridges Atomistics to Macroscale for Shock-to-Detonation Prediction
Simon Gonzalez-Zapata, Aidan Pantoya, Chunyu Li et al. (+2 more)
The shock-to-detonation transition in energetic materials is governed by coupled processes spanning Angstroms to millimeters and femtoseconds to microseconds, where traditional multiscale models fail due to the lack of scale separation. We address this grand challenge by directly bridging large-scale molecular dynamics (MD) simulations with continuum finite-element (FE) models using MISTnetX, a convolutional deep neural network. Trained on MD simulations of shock propagation through complex microstructures, MISTnetX captures shock-microstructure interactions, hotspot formation, and the transition to deflagration, supplying critical sub-grid information to FE simulations of mechanics, shocks, thermal transport, and chemistry. Applied to a synthetic but realistic nanostructured plastic-bonded RDX composite, MISTnetX enables parameter-free prediction of the full run-to-detonation transition.
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All authors Simon Gonzalez-Zapata, Aidan Pantoya, Chunyu Li, Marisol Koslowski, Alejandro Strachan
Mesoscale and Nanoscale Physics
Absence of a Superradiant Phase Transition in Dirac Landau Polaritons
Elsa Jöchl, Felix Helmrich, Frieder Lindel et al. (+6 more)
One of the most striking predictions in cavity
quantum electrodynamics is the condensation of
photons into a macroscopically populated ground state, the so-called superradiant phase transition (SRPT). SRPTs are theorized to occur in light-matter coupled systems above a critical coupling strength, yet have not been experimentally realized in
equilibrium. On the contrary, the very existence of SRPTs has been largely disputed by No-Go
theorems. In cavity-coupled electronic systems with Dirac dispersion, the diamagnetic $\vec{A}^2$-term crucial to No-go
theorems is not present at leading order, making
graphene Landau level transitions ultrastrongly coupled to terahertz cavities good candidates for SRPTs. In this work, we present the first terahertz spectroscopic measurements of an hBN-encapsulated monolayer
graphene flake coupled to a highly sub-wavelength resonator mode. By tuning the
graphene carrier density, we drive the resulting Landau polaritons into the ultrastrong coupling regime, with the normalized coupling reaching $\approx 40 \%$, approaching criticality. In this regime, the continuous SRPT would lead to a unique spectroscopic polariton softening, which we consistently rule out. The full polariton dispersion is instead quantitatively reproduced by a Hopfield
Hamiltonian using a quasistatic near-field model that accounts for the sub-wavelength character of the cavity.
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All authors Elsa Jöchl, Felix Helmrich, Frieder Lindel, Lucy Hale, Lorenzo Graziotto, Mona Jarrahi, Tobia F. Nova, Jérôme Faist, Giacomo Scalari
Soft Condensed Matter
Geometry and relaxation dynamics of nematic loops
F. Aprile, A. J. H. Houston, G. Gonnella et al. (+3 more)
Disclination lines in three-dimensional nematic
liquid crystals generically form closed loops whose
topology is classified by homotopy theory. While this classification successfully captures global topological features, it does not encode the geometry of the defect profile along the loop, which can strongly influence defect dynamics. Here, we propose a
geometric description of nematic disclination loops using the Clifford
algebra Cl(3,0). This approach naturally captures the geometry of the local defect profile, as well as changes along the loop, which is mathematically a SU(2) holonomy. Simulations of the dynamics of defect loops with specified geometries embedded in nematic
liquid crystals demonstrate that loops nucleate the growth of "topological blobs" of defects, which later dissipate leaving uniform nematic textures. Self-twist of the defect profile leads to nucleation of additional linking disclination lines, with a simple arithmetic relation between total self-twist and linking number. In contrast, loops with an even number of discrete profile transitions generate patterns with threading between loops, but no linking. These results establish a direct connection between the
geometric holonomy of a disclination loop and its subsequent
evolution, and may be extendable to more complex order parameter
manifolds, such as cholesterics or smectics.
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All authors F. Aprile, A. J. H. Houston, G. Gonnella, D. Marenduzzo, T. N. Shendruk, G. Negro
Mesoscale and Nanoscale Physics
Three Quantum-Geometric Contributions to Cubic Orbital Magnetization
T. Farajollahpour
In noncentrosymmetric metals such as $C_{3v}$ topological-
insulator surfaces, moiré heterobilayers, and zincblende
crystals, point-group
symmetry can forbid the linear and quadratic electric-field-induced orbital magnetization, leaving the cubic response as the leading signal. Using a Ward-complete finite-momentum cubic Kubo kernel with an antisymmetric linear-in-$q$ projection, we show that the dc response separates into three
quantum-
geometric channels. These are a mixed electric-
magnetic positional-shift quadrupole, a
quantum-metric drift term, and an orbital-moment octupole. The three contributions share the same point-group
symmetry but differ in their lifetime, frequency, and gate fingerprints. For a warped $C_{3v}$ surface the metric channel obeys the cutoff-independent law $\bar{\chi}_G \propto \mu^{-2}$. We propose third-harmonic magneto-optical Kerr spectroscopy as an experimental route.
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Statistical Mechanics
Non-stationary current fluctuations in 1D boundary-driven diffusive systems via Macroscopic Fluctuation Theory
Daisuke Suzuki and Tomohiro Sasamoto
While Macroscopic Fluctuation Theory (MFT) has been highly successful in analyzing non-
equilibrium steady states, its application to non-steady-state processes remains limited. In this study, we apply MFT to the relaxation process of one-dimensional boundary-driven diffusive systems coupled to particle reservoirs at both ends. We exactly derive the current variance for systems with a constant
diffusion coefficient and arbitrary mobility, as well as the cumulant generating function for the current in Reflective Brownian Motion (RBM). Our results demonstrate that non-steady current fluctuations during the approach to a steady state can be quantitatively described within the MFT framework.
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Soft Condensed Matter
Resolving Capillary Mode Transitions in Microparticles at Fluid Interfaces
Sungwan Park, Justin Jeongwoo Choi and Albert Tianxiang Liu
Capillarity-driven self-assembly at fluidic interfaces offers a scalable route to large, reconfigurable materials. Microscale particles with high horizontal-to-vertical aspect ratios become attractive building blocks for shape-directed organization, but the capillary rules governing their assembly remain incompletely understood. Here, we combine experiments and theory to explain the transition between two capillary regimes: monopolar interactions arising from millimeter-scale curved interfaces, and quadrupolar interactions arising from local contact-line distortions. We show that the conventional Bond number is insufficient to predict this transition because it omits key material and surface-topography effects. Instead, we identify a new dimensionless parameter that captures the coupled roles of particle size, density, surface roughness, contact angle, and quadrupolar strength. This criterion correctly predicts when gravitationally induced monopolar attraction or surface-pinning-induced quadrupolar attraction dominates, providing a general design rule for interfacial particle assembly. The resulting model explains how particles self-organize across length scales and offers guiding principles for engineering next-generation interfacial materials from miniaturized particulate building blocks.
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Materials Science
Atomically precise mechanosynthesis of carbon structures on hydrogenated Si(100) by inverted-mode STM
Megan Cowie, Chris Deimert, Ryan Groome et al. (+44 more)
The ability to build atomically precise structures on surfaces with complete control over both atomic placement and chemical bonding remains a central challenge in nanoscale fabrication. Here, we demonstrate simultaneous spatial and chemical control over the mechanosynthetic fabrication of carbon structures. Using inverted-mode STM, C$_2$ units are donated from surface-deposited molecules to pre-patterned reactive sites on a hydrogen-passivated Si(100) surface. We demonstrate single-site C$_2$ donation, spatially patterned multi-site C$_2$ donation, and the stepwise assembly of polyyne structures through successive C-C bond formation. Together, these results establish controlled mechanosynthetic donation as a foundational capability for programmable atomically precise fabrication.
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All authors Megan Cowie, Chris Deimert, Ryan Groome, Alex Inayeh, Robert J. Kirby, Cameron J. Mackie, Jonathan Myall, Sam Rohe, Luis Sandoval, Khalil Sayed-Akhmad, Bheeshmon Thanabalasingam, Reid Wotton, Rafik Addou, Aly Asani, Brandon Blue, Adam Bottomley, Kareem A. Clarcia, Tyler Enright, James Zhangming Fan, Robert A. Freitas Jr., Alan T.K. Godfrey, Si Yue Guo, Aru Hill, Taleana Huff, Mark Jobes, Hadiya Ma, Adam C. Maahs, Oliver MacLean, Steven M. Maley, Michael Marshall, Terry McCallum, Ralph C. Merkle, Mathieu Morin, Ryan Plumadore, Henry Rodriguez, Marc Savoie, Benjamin Scheffel, Janice L. Wong, Damian G. Allis, Jeremy Barton, Michael Drew, Matthew R. Kennedy, Tait Takatani, Marco Taucer, Dusan Vobornik, Ryan Yamachika, Mathieu Durand
Materials Science
At-Scale Discovery of High-Voltage Cathode Active Materials for Na-Ion Batteries via Charged-Only Structures and Committee Divide-and-Conquer Learning
Suchona Akter, Md Omar Faruque and Mohammad R. Momeni
Current cathode-active materials (CAMs) designed for sodium-ion batteries (SIBs) suffer from low operating voltages, limited energy density, irreversible phase transitions, and low intrinsic electrical conductivity. In this work, we have developed generalizable and transferable descriptor-based machine learning (ML) models, along with composition- and graph-based neural networks (NNs) and transfer learning (TL) models, all trained on a
dataset of charged-only structures rather than charged/discharged pairs. Using a committee of the top four trained ML models, the mean voltage is predicted as the target property. More importantly, we show that uncertainty quantification can improve the reliability of candidate selection for training subsequent higher-generation models by including structures for which the current committee models are least confident. In this way, the new expensive ab initio data provide information in regions where the original models most need improvement. We have showcased the transferability of the final generation models by applying them to a large database of Na-free inorganic host structures curated from Materials Project, AFLOW, OQMD, and GNoME for at-scale SIB CAM discovery. A comprehensive interactive online database, NaCAM-Atlas, was also developed, containing 14,843 CAMs with voltages greater than 3 V for SIBs. Finally, a subset of the top-ranked candidate CAMs was validated through explicit, high-throughput first-principles calculations of voltage profiles, structural robustness upon sodiation/desodiation, and electronic properties. Together, this integrated data curation, ML training and improvement, and first-principles validation strategy establishes a scalable and transferable framework for accelerating the discovery of stable, high-voltage CAMs for SIBs and beyond.
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Statistical Mechanics · Cross-listed from quant-ph
Bose-Einstein thermal operators for semidefinite optimization
Michele Minervini, Nana Liu and Mark M. Wilde
We establish that semidefinite programs (SDPs) over the unbounded positive semidefinite cone are mathematically equivalent to thermodynamic systems of independent bosonic modes: the
eigenvalues of the optimization variable play the role of expected occupation numbers, the linear objective plays the role of total expected energy, and the linear equality constraints play the role of conserved non-commuting charges. Building on this perspective, we recast general SDPs as bosonic free-energy minimization problems at strictly positive temperature, regularized by the Bose-Einstein
entropy; the original SDP is recovered in the zero-temperature limit. The optimal primal variable takes the form of a Bose-Einstein thermal operator parametrized by the dual variables. We prove an approximation-error bound that depends on the ground-space degeneracy and the spectral gap of the dual slack operator, improving on the linear-in-dimension worst-case duality gap of interior-point methods. We also introduce the Bose-Einstein
quantum relative
entropy as a Bregman divergence on the unbounded positive semidefinite cone, generated by the negative Bose-Einstein
entropy. We propose it as a natural divergence for unnormalized positive operators, for which the standard Umegaki relative
entropy can become negative, and we show that it satisfies a restricted monotonicity property under affine maps modeling bosonic Gaussian channels. Finally, we develop hybrid
quantum-classical
algorithms for the regularized SDP using only
Hamiltonian simulation, Hadamard tests, and classical sampling, and bound their runtime in closed form. Unlike existing
quantum SDP solvers, whose runtimes scale polynomially with an a priori upper bound on the primal trace, our framework operates directly on the unbounded cone, replacing this bound with a dependence on the spectral structure of the dual slack operator.
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Materials Science
Disordered vs. Short-Range-Ordered Complexions: Consequences for Grain-Boundary-Mediated Plasticity in Nanocrystalline Al-Ni Alloys
Frederic Sansoz and Eve-Audrey Picard
Disordered grain-boundary (GB) complexions in thermally stable nanocrystalline
alloys are commonly assumed to be structurally uniform, yet their amorphous nature makes them susceptible to local short-range ordering (SRO). The influence of local SRO on GB-mediated plasticity mechanisms in such complexions remains poorly understood. This article employs large-scale Monte Carlo and molecular dynamics simulation to address this gap through simulations of nanocrystalline Al-Ni
alloys at two Ni concentrations, 2 at.% and 4 at.%. Annealing at 913 K produces thick uniform disordered intergranular film complexions, while annealing at 378 K produces semi-disordered complexions containing FCC-type and BCC-type SRO. These two complexion states produce fundamentally different mechanical responses. Amorphous complexions act as dislocation sinks, promoting homogeneous plasticity through shear transformation zones, but at the cost of intense shear localization and lower strength. SRO complexions generate reduced shear localization and higher strength but also promote heterogeneous stress concentrations across the GB network, regardless of Ni concentration. This contrast reflects a fundamental shift in governing mechanism, from shear-transformation-zone-controlled behavior in disordered complexion
alloys to GB-stress-heterogeneity-controlled behavior in SRO complexion
alloys. These findings highlight the potential of complexion engineering to tailor the mechanical properties of nanocrystalline materials.
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Mesoscale and Nanoscale Physics
High-mobility inertial domain walls driven by spin-transfer torque in a ferrimagnetic spinel oxide
Mingxing Wu, Shilei Ding, Laura van Schie et al. (+8 more)
Efficient electrical manipulation of domain walls is key to developing
magnetic devices with fast switching capabilities and low energy consumption. Here we demonstrate Bloch-type domain wall velocities exceeding 1 km s$^{-1}$ in the single-layer ferrimagnetic spinel
oxide NiCo$_2$O$_4$ induced by
spin-transfer torque at a current density of $2 \times 10^{11}$ A m$^{-2}$. This exceptional domain wall mobility is attributed to the combination of
giant nonadiabatic
spin-transfer torque, low magnetization, and high
spin polarization. Additionally, we report a pronounced domain wall inertia effect in this ferrimagnet due to the large nonadiabaticity of the torque. The characteristic time for domain wall acceleration and deceleration is $\sim 1$ ns, shorter than that reported for typical ferromagnets. Our findings highlight the potential of spinel
oxides as a promising platform for engineering high-performance domain wall devices that take advantage of ultrafast ferrimagnetic dynamics.
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All authors Mingxing Wu, Shilei Ding, Laura van Schie, Shenghao Cai, Yuhao Qiu, Ao Du, Alexander E. Kossak, Rui Wu, Christian L. Degen, Xuegang Chen, Pietro Gambardella
Mesoscale and Nanoscale Physics
Orbital and Spin-Orbit Torque Interplay in Ta/W-based Magnetic Tunnel Junctions with Vertical Non-local Switching
Marco Biagi, Corrado C. M. Capriata, K. Subham Senapati et al. (+6 more)
Spin-orbit torque (SOT) enables ultra-fast, energy-efficient magnetization switching, making it a promising mechanism for introducing MRAMs for cache
memory applications. However, current SOT-MRAM devices face write efficiency limitations, with charge-to-
spin conversion ($\xi_{DL}$) reaching $\sim$ 45%, far below the projected $\sim$ 80% needed to comply with the current delivery of advanced transistor nodes. Recent advances in orbital current physics, evidenced in a wide class of materials, offer a path to enhance $\xi_{DL}$. Here, we study the Ta(3-30 nm)\slash W(1-4 nm) system, revealing a large additional
spin-orbit torque contribution arising from Ta, a four-fold increase compared to the
spin Hall effect in Ta alone, attributed to the orbital
Hall contribution. This system exhibits larger $\xi_{DL}$ than W-based SOT systems with more robust perpendicular
magnetic anisotropy and compatibility with 400$^\circ$C annealing. Leveraging these advantages, we integrate the Ta/W system into 3-terminal SOT-MTJ devices, showing a level of performance similar to that of W-based systems. Our results show that orbital physics can be easily integrated into SOT-MTJ systems, offering a viable strategy to enhance SOT-MRAM efficiency. In addition, we propose and demonstrate a proof-of-concept for vertical non-local switching of SOT-MTJ using orbital torques, simplifying bottom-pinned SOT-MRAM fabrication.
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All authors Marco Biagi, Corrado C. M. Capriata, K. Subham Senapati, Ioannis Trikoilis Koll, Corentin Bouchard, Ricardo C. Sousa, Louis Hutin, Bernard Viala, Kevin Garello
Strongly Correlated Electrons · Cross-listed from quant-ph
Gonzalo Camacho and Benedikt Fauseweh
Time
crystals are nonequilibrium phases of matter characterized by the emergence of temporal ordering, in which an interacting many-body system develops robust structure in its time
evolution that is not trivially dictated by the external driving or environment. While related phenomena have long been studied in classical nonlinear systems, their realization in entangled
quantum matter represents a distinct frontier. The theoretical understanding of discrete time
crystals has substantially advanced, yet recent experiments using modern
quantum devices and
quantum processors reveal regimes beyond established paradigms. These developments call for an extended classification of time-crystalline phases according to both their stabilization mechanisms and their physical character, including discrete and continuous, closed and open, critical, topological, quasiperiodic, and controlled realizations. We review recent implementations of time
crystals on
quantum platforms and propose such a classification framework, identifying promising directions for the discovery of novel time-crystalline phases of matter.
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Statistical Mechanics · Cross-listed from cs.CY
Queue & AI: When Faster Tasks Slow Down the Workflow
Silvia Bartolucci and Pierpaolo Vivo
Quantifying the workplace productivity effects of Generative Artificial Intelligence is now central to economics, management, and public policy. The deployment of AI tools in customer service, writing, software development, and consulting operations has been reported to generate large per-task productivity gains, typically measured as tasks completed per worker-hour or reductions in mean handle time. We argue that such mean-based metrics can misrepresent AI's effects in workflows where tasks accumulate and compete for scarce human
attention. AI assistance can generate a deceptive productivity signature: average completion times fall because AI tools typically supply a fast first draft, yet workflow-level performance deteriorates when a subset of AI errors escapes review and returns as costly downstream rework. We call this divergence between mean task speed and system-level delay the variance wedge. Depending on the operational parameters, the most time-efficient way to complete a workflow may undergo a transition between two task-processing regimes, a fully AI-assisted and a fully manual one. We formalize the mechanism as a queueing model and derive two main implications analytically. First, under congestion, reviewers rationally raise the risk threshold for checking AI outputs, reducing scrutiny precisely when it would matter the most. Second, AI assistance can stabilize an overloaded workflow only when (i) the fraction of tasks handled by AI exceeds a critical threshold, and (ii) the human
attention required for review and expected rework is lower than the
attention for manual completion, a requirement substantially more stringent than faster draft generation. These results suggest that AI deployment should be evaluated not only by average task speed, but by its overall effects on congestion, rework, and the robustness of human oversight under load.
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Superconductivity
Electride States and Superconductivity in Dense Potassium Carbides
Jiance Sun, Ting Zhong and Shoutao Zhang
Metal carbides have attracted a great deal of
attention due to their diverse
geometric motifs, remarkable physicochemical properties, and widespread practical applications. However, there is still a lack of systematic understanding regarding the phase diagram of pressurized potassium carbide. Employing first-principles swarm-intelligence structure prediction approach, we comprehensively explore the binary potassium-carbon phases under compression and identify a series of new K-rich and C-rich stoichiometric compounds. Among them, K7C with high K concentration manifests a monoclinic structure with space group C2/m and is predicted to be an electride with zero-dimensional (0D) interstitial electrons. C-abundant KC has an orthorhombic configuration with
symmetry Imma, with the carbon atoms arranged in a zigzag pattern. Strikingly, KC3, belonging to a monoclinic C2/m structure, possesses the highest carbon content and features a crumpled honeycomb carbon layer. Furthermore, calculations of electron-
phonon coupling reveals that K7C is a 0D electride
superconductor with a transition temperature (Tc) of 0.6 K at a pressure of 25 GPa. By contrast, KC exhibits a maximum Tc of 21.4 K at 25 GPa, which is primarily attributed to the robust coupling between low-frequency K- and C-derived
phonon modes and C 2p electrons at the
Fermi level. In addition, KC3 is calculated to have a Tc value of 6.7 K at 25 GPa. This study provides valuable insights into K-C compounds and broadens the diversity of metal carbide
superconductors.
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Statistical Mechanics
Quantum fluctuations and chaos in fully connected spin models
Aleksandra A. Ziolkowska and Aleksandr N. Mikheev
We investigate beyond-mean-field dynamics in a fully connected $\mathrm{SU}(3)$
spin-exchange model, focusing on the interplay between chaotic dynamics and
quantum fluctuations. Using the two-particle irreducible (2PI) effective action formalism, we derive equations of motion that systematically account for higher-order correlations generated by interactions, and demonstrate how
quantum fluctuations can regularize chaotic dynamics displayed by macroscopic observables. Our results show that an accurate treatment of fluctuations is essential for describing macroscopic dynamics in
quantum many-body systems and promote 2PI as a robust framework for connecting microscopic correlations to macroscopic nonequilibrium phenomena.
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Strongly Correlated Electrons
Algebras of order parameters in one-dimensional spin systems
Ameya Chavda, Clement Delcamp, Alex Turzillo et al. (+1 more)
We study order parameters in one-dimensional
quantum lattice models with finite invertible or non-invertible
symmetry. We investigate what properties a string operator must satisfy in order to acquire a non-vanishing expectation value in a given gapped phase. We deduce that multiplets of string order parameters organise into a Lagrangian
algebra in the Drinfel'd centre of the
symmetry category. In particular, we highlight the role of the multiplication rule as governing the fusion of the twisted sector local operators that constitute the string operator in the infrared limit. Our derivations exploit the tensor network approach to the classification of gapped phases and its reformulation in terms of module categories over the
symmetry category. Within this framework, a gapped phase is associated with a pattern of spontaneous
symmetry breaking wherein a Morita class of
algebras of topological lines is preserved in the ground state subspace. The crux of the proof is to show that the expectation value of any string operator explicitly depends on the tube
algebra module associated with the Lagrangian
algebra, which is realised as the full centre of the corresponding module category. Finally, we demonstrate that these techniques extend to phases of symmetric mixed states.
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All authors Ameya Chavda, Clement Delcamp, Alex Turzillo, Minyoung You
Mesoscale and Nanoscale Physics
Overcoming contact resistance at metal-2D semiconductor interfaces: atomically clean MoS2/Au ohmic junctions
Rafal Dunal, Maxime Le Ster, Iaroslav Lutsyk et al. (+8 more)
The application of two-dimensional (2D)
semiconductors, such as monolayer MoS2, is limited by the high contact resistance commonly attributed to interfacial barriers at metal contacts. Furthermore, the dependence of electrical conductivity on MoS2 thickness is still unsettled, as both increasing and decreasing trends with layer number have been reported. By showing the contrast between electrical transport of mono- and multilayer MoS2 exfoliated on Au under ultra-high
vacuum (UHV) and ambient conditions, we experimentally prove that, contrary to the prevailing view in the literature, the intrinsic MoS2/Au junction is highly conductive and exhibits ohmic behaviour. Our results indicate that interfacial contamination is responsible for the high contact resistances reported to date and affects the thickness dependence of electrical transport, explaining the discrepancies observed in the literature. We rationalize those findings using electrical transport simulations. Lastly, we show that local force-mediated lamination on lightly contaminated contacts can recover pristine, ohmic contacts, offering a route towards nanoscale patterning.
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All authors Rafal Dunal, Maxime Le Ster, Iaroslav Lutsyk, Michal Piskorski, Pawel Dabrowski, Pawel Krukowski, Witold Kozlowski, Aleksandra Nadolska, Wojciech Rys, Pawel J. Kowalczyk, Maciej Rogala
Mesoscale and Nanoscale Physics
Microwave-driven Floquet-Fano interference in a ring-chord quantum dot structure for enhanced spin-caloritronic performance
Parbati Senapati and Kalpataru Pradhan
We investigate
photon-assisted thermoelectric transport in four–
quantum-dot nanostructures featuring ring and ring–chord geometries coupled to
ferromagnetic leads. Focusing on the interplay between microwave-induced Floquet sidebands and geometry-driven Fano interference, we employ the nonequilibrium Green's function formalism combined with Floquet theory and a self-consistent Hartree treatment of electron-electron interactions within the linear response regime. The inclusion of a longitudinal interdot chord bridging the lead-coupled dots introduces a discrete interference pathway that competes with the continuum of ring-mediated states, giving rise to pronounced Fano resonances. Microwave irradiation dynamically reshapes these resonances through
photon absorption and emission processes, enabling tunable control of electrical conductance, thermopower, and electronic thermal conductance. Quantitatively, at an intermediate temperature of $T=0.3\Gamma_0$ (where $\Gamma_0$ denotes the dot-lead coupling strength), the microwave-driven ring-chord geometry exhibits an exceptional thermoelectric figure of merit of ZT $\approx$ 12 and an optimal efficiency–power trade-off, reaching nearly $62\%$ of the Carnot efficiency with an output power of $6.24~\mathrm{fW}$. Crucially, the combination of
spin-polarized injection from the leads and Zeeman splitting within the dots induces a robust
spin-dependence within this Floquet–Fano interference. This cooperative interplay results in an enhanced
spin Seebeck response and a maximum
spin thermoelectric figure of merit of nearly $Z_sT \approx 18$. Our findings establish microwave-driven engineering of Fano interference as an effective strategy for modulating
spin-caloritronic behavior in multi-
quantum-dot devices.
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Superconductivity
Impact of Stoichiometry of MoSi Thin Films for Enhanced Sensitivity of Superconducting Nanowire Single-Photon Detectors
Stefanie Grotowski, Damjan Pecijareski, Hadrien Le Petit Delacour et al. (+8 more)
We report on the impact of the stoichiometry of superconducting MoSi thin films on the performance of superconducting nanowire single-
photon detectors (SNSPDs). Specifically, we investigate the relation between the film parameters critical temperature Tc , sheet resistance Rs and
superconductor thickness d and observe a universal scaling behavior. To
benchmark the performance of SNSPDs fabricated from films having different stoichiometry, we measure the bias dependent count rate curves, while the detector is illuminated with wavelengths between 780 nm and 1550 nm. The detector performance as a function
photon energy for different nanowire widths reveals a linear relation between the detection current and the
photon energy. Furthermore, we determine the interfacial thermal boundary conductance $\beta$ between the superconducting thin film and the substrate, by measuring the return current of the SNSPD and find an increase of $\beta$ with increasing Mo concentration. The highest sensitivity amongst all compared devices is achieved for Mo$_{0.53}$Si$_{0.47}$, with low Tc (4.1 K) and high Rs (397$\Omega$/sq) at a film thickness of 5.4 nm.
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All authors Stefanie Grotowski, Damjan Pecijareski, Hadrien Le Petit Delacour, Lucio Zugliani, Fabian Wietschorke, Christian Schmid, Stefan Strohauer, Matthias Althammer, Rudolf Gross, Kai Müller, Jonathan Finley
Strongly Correlated Electrons
Quantum criticality and factorization in a constrained Rydberg spin chain
Yuan Jiang, Wen-Long You, Liangsheng Li et al. (+1 more)
We investigate the zero-temperature phase diagram of a one-dimensional constrained
quantum spin chain realized in coherently driven Rydberg-atom arrays with competing local Rabi driving and dipole-dipole exchange interactions. Projecting onto the blockade-constrained
Hilbert space yields an effective model in which local and nonlocal
quantum fluctuations compete on equal footing. Combining exact diagonalization, the density-
matrix renormalization group, and variational uniform
matrix-product-state calculations, we establish a complete phase diagram comprising a Luttinger
liquid, an
antiferromagnetic ordered phase, and a polarized paramagnet. We identify two distinct mechanisms for the destruction of
antiferromagnetic order: a conventional Ising transition at strong driving and a continuous
quantum melting into the Luttinger
liquid at weak driving, characterized using
entanglement-based diagnostics and finite-
entanglement scaling. In addition, we uncover an exact ground-state factorization line embedded within the ordered phase, providing an analytically tractable zero-
entanglement reference point for experiments with programmable Rydberg
quantum simulators.
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All authors Yuan Jiang, Wen-Long You, Liangsheng Li, Maoxin Liu
Materials Science
Rapid estimation of synthesizability windows of inorganic materials from first principles
Finja Tadge, Javier Sanz Rodrigo and Andrea Crovetto
Fast prediction of the synthesizability conditions of materials remains challenging, even assuming synthesis under thermodynamic
equilibrium. We combine density functional theory (DFT) with machine-learned interatomic potentials to enable high-throughput generation of phase predominance diagrams as a function of temperature and partial pressures of the gaseous reactants. These diagrams can immediately be used by experimentalists to translate computational predictions into real synthesis parameters in the lab. Predominance diagrams are generated for a diverse set of binary compounds and for 48 more complex ternary metal phosphosulfide systems, but the method is in principle scalable to any inorganic material class. The calculated predominance diagrams generally show good agreement with the experimental synthesis literature, with a drastic reduction in computational cost compared to a full DFT approach. We find several examples of compounds that appear as metastable in a zero-temperature stability hull picture, but that become thermodynamically stable under well-defined synthesis windows.
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Materials Science
Simplified criteria for identifying and designing altermagnetic crystals in real space
Ying Chen, Qiushi Huang, Yu Wu et al. (+2 more)
Altermagnetism is a compensated
magnetic phase characterized by zero net magnetization and exchange-driven
spin splitting. However, identifying altermagnets among collinear antiferromagnets usually requires full
magnetic-space-group or
spin-group analysis, which is not always intuitive. Here we formulate a simple real-space criterion based on how the crystallographic operations of the host nonmagnetic structure permute the two opposite-
spin sublattices. We show that altermagnets usually exist on collinear compensated antiferromagnets whose
magnetic primitive
cell coincides with the host nonmagnetic crystallographic primitive
cell. In this case, altermagnetic
spin splitting is generally allowed unless an inversion-type operation exists that exchanges the two opposite-
spin sublattices. Using chemically ordered Mn2SSe prototypes derived from zinc-blende or rocksalt parent structures, we demonstrate that these criteria can be easily used to construct the three
symmetry classes by controlling chemical ordering and
magnetic-sublattice permutation. Similar rules can also be applied to low-dimensional
crystals or quasicrystals. Our work reduces the identification of altermagnets to a transparent real-space
symmetry test and provides a practical route for designing altermagnetic
crystals.
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All authors Ying Chen, Qiushi Huang, Yu Wu, Xiaolan Yan, Su-Huai Wei
Statistical Mechanics
Subdiffusion equation with Cattaneo effect
Tadeusz Kosztołowicz, Aldona Dutkiewicz and Katarzyna D. Lewandowska
The ordinary subdiffusion equation, with a fractional time derivative of at most first order, describes a process in which the propagation velocity of diffusing molecules is unlimited. To avoid this non-physical property different forms of the Cattaneo subdiffusion equation have been proposed. We define the Cattaneo effect as a delay of the ordinary subdiffusion flux activation by a random time. By incorporating this effect into the flux equation we get a Cattaneo–type subdiffusion equation (CTSE). We consider a subdiffusion process in which the Cattaneo effect is generated by the time-delay probability distribution controlled by the Mittag-Leffler function. Then, CTSE differs from the ordinary subdiffusion equation by a term with a fractional time derivative, whose order can be independent of the subdiffusion exponent. The influence of the Cattaneo effect on the solutions to the CTSE is discussed. We show that the process described by CTSE is subdiffusion in the entire time domain even though the temporal
evolution of the mean square displacement of diffusing particle in the short-time limit is typical for superdiffusion. The delay in the flux activation in the subdiffusion equation should also cause a flux delay in a boundary condition. As an example, we study subdiffusion with the Cattaneo effect in a system with a partially absorbing wall at which the Robin boundary condition is assumed. We also propose a method for experimentally identifying the Cattaneo effect in a subdiffusive system.
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Materials Science
Light-induced Faraday effect from dynamical breakdown of Kleinman symmetry
Niccolò Sellati, Jacopo Fiore and Lara Benfatto
The observation of anomalously large polarization rotations in pump-probe experiments with circularly polarized light has recently challenged the conventional understanding of the inverse Faraday effect. The striking magnitude of these responses implies the generation of effective
magnetic fields orders of magnitude larger than theoretical expectations, raising fundamental questions about the nature of light-induced time-reversal
symmetry breaking. In this work we demonstrate that a static polarization rotation can originate entirely from the antisymmetric component of the third-order optical susceptibility, without generating a macroscopic magnetization of the material. We show that this light-induced Faraday effect is inherently dynamical, emerging when Kleinman
symmetry breaks down. Using a minimal $sp$ tight-binding model on a square
lattice, we demonstrate that the light-induced Faraday response can be sizable even far from dissipative resonances. While the effect emerges at a purely electronic level, we show that resonant coupling with
phonons can significantly enhance the pump-probe response. Finally, we demonstrate that the light-induced Faraday contribution can strongly exceed the magneto-optical response mediated by the inverse Faraday effect in nonmagnetic materials.
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Mesoscale and Nanoscale Physics · Cross-listed from physics.ins-det
A Levitated Random Telegraph Noise Spectrometer
Molly Message, Bianca C. J. Uy, Katie O'Flynn et al. (+7 more)
Random Telegraph Noise is a ubiquitous process manifesting across technology and the natural world. It is characterized by random jumps between two distinct states with Poissonian waiting times, and is the origin of 1/f noise. Understanding and characterizing this noise is critical for the reliable operation of micro-, nano- and
quantum-technologies. In this work we probe random telegraph noise using a levitated microparticle sensor whose dynamics are driven almost entirely by this non-white source of noise. We observe a startling resonant behaviour, characterized by a thousand-fold increase in the underdamped sensor's position fluctuations, enabling us to measure the spectral properties of the noise over six decades of timescale. This work not only provides a unique way to probe random telegraph noise, but also demonstrates a platform for studying non-
equilibrium stochastic dynamics in the presence of realistic non-white noise, with applications from biology to social behaviour.
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All authors Molly Message, Bianca C. J. Uy, Katie O'Flynn, Yugang Ren, Muddassar Rashid, Jonathan D. Pritchett, Qiongyuan Wu, Hyukjoon Kwon, Benjamin A. Stickler, James Millen
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Quantifying the liquid flow between a soap film and a vertical meniscus
Alexandre Vigna-Brummer, Simon Cox, Médéric Argentina et al. (+2 more)
Fluid exchange between a soap film and its bounding menisci governs film drainage and stability, with direct implications for the lifetime of surface bubbles and
liquid foams. Despite recent advances, a quantitative characterization of this coupling, associated with the phenomenon of marginal regeneration, remains incomplete. The volumetric flux per unit length of contact follows a well-established scaling law involving geometrical parameters such as the film height and the meniscus radius of
curvature. However, the dimensionless prefactor of this relation - the flux coefficient - remains difficult to determine for vertical menisci because of the complex and intermittent flows occurring at the film-meniscus interface. Here, we quantify this flux into the meniscus generated by inserting a solid plate into a vertical soap film. We consider both vertical and inclined plates and further investigate the effects of plate inclination, height, and width. Focusing on the dynamics of the growth of the meniscus driven by
liquid supplied by the film, we analyze both steady and transient regimes resulting from the interplay between capillary pressure,
gravity, and
liquid exchange. Combining experiments, numerical simulations, and theoretical modelling, we determine the flux coefficient using three independent methods and show that it remains constant over the range of parameters explored.
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All authors Alexandre Vigna-Brummer, Simon Cox, Médéric Argentina, Christophe Brouzet, Christophe Raufaste