Strongly Correlated Electrons
TeMFpy: a Python library for converting fermionic mean-field states into tensor networks
Simon H. Hille and Attila Szabó
We introduce TeMFpy, a Python library for converting fermionic mean-field states to finite or infinite
matrix product state (MPS) form. TeMFpy includes new, efficient, and easy-to-understand
algorithms for both Slater determinants and Pfaffian states. Together with Gutzwiller projection, these also allow the user to build variational wave functions for various strongly correlated electron systems, such as
quantum spin liquids. We present all implemented
algorithms in detail and describe how they can be accessed through TeMFpy, including full example workflows. TeMFpy is built on top of TeNPy and, therefore, integrates seamlessly with existing MPS-based
algorithms.
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Strongly Correlated Electrons
Spin-spiral instability of the Nagaoka ferromagnet in the crossover between square and triangular lattices
Darren Pereira and Erich J. Mueller
We study the hard-core
Fermi-Hubbard model in the crossover between square and triangular
lattices near half-filling. As was recognized by Nagaoka in the 1960s, on the square
lattice the presence of a single hole leads to
ferromagnetic spin ordering. On the triangular
lattice,
geometric frustration instead leads to a
spin-singlet ground state, which can be associated with a 120-degree spiral order. On
lattices which interpolate between square and triangular, there is a phase transition at which the
ferromagnetic order becomes unstable to a
spin spiral. We model this transition, finding the exact location of the
spin-spiral instability.
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Superconductivity
Superfluid weight in disordered flat-band superconductors as a competition between localization functionals
Kryštof Kolář, Tero T. Heikkilä and Päivi Törmä
According to Anderson's
theorem, the gap of a time-reversal symmetric weak-coupling
superconductor is unaffected by non-
magnetic disorder. However, the superfluid weight (stiffness) is reduced in the disordered limit by a factor of $\Delta \tau$, a product of the scattering time $\tau$ and the superconducting order parameter $\Delta$. Here we show that the opposite holds true in flat-band
superconductors. While non-
magnetic disorder does reduce the order parameter, we find that its direct effect on superfluid weight is mostly negligible. We show analytically that the effect of disorder is to lowest order given in terms of the difference between the intraband and interband parts of the localization functional of
impurity wavefunctions, finding it to be typically vanishing.
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Statistical Mechanics
Scalable accuracy gains from postselection in quantum error correcting codes
Hongkun Chen, Daohong Xu, Grace M. Sommers et al. (+3 more)
Decoding stabilizer codes such as the surface and toric codes involves evaluating free-energy differences in a disordered statistical mechanics model, in which the randomness comes from the observed pattern of error syndromes. We study the statistical distribution of logical failure rates across observed syndromes in the toric code, and show that, within the coding phase, logical failures are predominantly caused by exponentially unlikely syndromes. Therefore, postselecting on not seeing these exponentially unlikely syndrome patterns offers a scalable accuracy gain. In general, the logical error rate can be suppressed from $p_f$ to $p_f^b$, where $b \geq 2$ in general; in the specific case of the toric code with perfect syndrome measurements, we find numerically that $b = 3.1(1)$. Our arguments apply to general topological stabilizer codes, and can be extended to more general settings as long as the decoding failure probability obeys a large deviation principle.
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All authors Hongkun Chen, Daohong Xu, Grace M. Sommers, David A. Huse, Jeff D. Thompson, Sarang Gopalakrishnan
Quantum Gases
Effects of intertube dipole-dipole interactions in nearly integrable one-dimensional $^{162}$Dy gases
Yicheng Zhang, Kangning Yang, Benjamin L. Lev et al. (+1 more)
We study the effects of the intertube dipole-dipole interactions (DDI) in recent experiments with arrays of nearly integrable one-dimensional (1D) dipolar Bose gases of $^{162}$Dy atoms. An earlier theoretical modeling ignored those interactions, which we include here via a modification of the 1D confining potentials. We investigate the effects of the intertube DDI both during the state preparation and during the measurements of the rapidity distributions. We explore how the strength of the contact interactions and the
magnetic field angles modify the intertube DDI corrections. We find that those corrections slightly change both the properties of the
equilibrium state and the rapidity measurements. Remarkably, however, the changes nearly cancel each other, resulting in measured rapidity distributions that are very close to those predicted in the absence of the intertube DDI.
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All authors Yicheng Zhang, Kangning Yang, Benjamin L. Lev, Marcos Rigol
Strongly Correlated Electrons · Cross-listed from quant-ph
Self-dual bivariate bicycle codes with transversal Clifford gates
Zijian Liang and Yu-An Chen
Bivariate bicycle codes are promising candidates for high-threshold, low-overhead fault-tolerant
quantum memories. Meanwhile, color codes are the most prominent self-dual CSS codes, supporting transversal Clifford gates that have been demonstrated experimentally. In this work, we combine these advantages and introduce a broad family of self-dual bivariate bicycle codes. These codes achieve higher encoding rates than surface and color codes while admitting transversal CNOT, Hadamard, and $S$ gates. In particular, we enumerate weight-8 self-dual bivariate bicycle codes with up to $n \leq 200$ physical
qubits, realized on twisted
tori that enhance code distance and improve stabilizer locality. Representative examples include codes with parameters $[[n,k,d]]$: $[[16,4,4]]$, $[[40,6,6]]$, $[[56,6,8]]$, $[[64,8,8]]$, $[[120,8,12]]$, $[[152,6,16]]$, and $[[160,8,16]]$.
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Strongly Correlated Electrons
Vestigial $d$-wave charge-$4e$ Superconductivity from Bidirectional Pair Density Waves
Ethan Huecker and Yuxuan Wang
We analyze the leading vestigial instability due to the melting of a bidirectional pair-density-wave state in two dimensions. In a previous work by one of the authors, it was found that the interplay between pair-density-wave fluctuations with ordering momenta along the $x$ and $y$ directions can provide a strong attractive interaction for charge-$4e$ superconductivity in the $d$-wave channel. In this work, we go beyond the artificial large-$M$ mean-field theory previously adopted and compute the phase diagram by incorporating phase fluctuations of the pair-density-wave order parameters. By investigating the relevance of various topological defects, we show that the interaction in the $d$-wave channel, together with the strong anisotropy of phase fluctuations around the pair-density-wave ordering momenta, favors a vestigial charge-$4e$ superconducting order at intermediate temperatures. By contrast, a competing charge-density-wave vestigial order does not develop, due to the suppression of its stiffness.
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Strongly Correlated Electrons
Casimir Stabilization of Fluctuating Electronic Nematic Order
Ola Carlsson, Sambuddha Chattopadhyay, Jonathan B. Curtis et al. (+4 more)
Vacuum cavity control of
quantum materials is the engineering of
quantum materials systems through electromagnetic zero-point fluctuations. In this work we articulate a generic mechanism for
vacuum optical control of correlated electronic order: Casimir control, where the zero-point energy of the electromagnetic continuum, the Casimir energy, depends on the properties of the material system. To assess the experimental viability of this mechanism we focus on the Casimir stabilization of fluctuating nematic order. In nematic
Fermi liquids, different orientations of the electronic order are often energetically degenerate. Thus, while local domains of fixed orientation may form, thermal disordering inhibits long range order. By engineering the electromagnetic environment of the electronic system, however, we show that the Casimir energy can be used as a tool to preferentially stabilize particular orientations of the nematic order. As a concrete example, we examine the interplay between a birefringent
crystal – which sources an anisotropic electromagnetic environment – and a
quantum Hall stripe system, an archetypal nematic
Fermi fluid. We show that for experimentally feasible setups, the anisotropy induced by the orientation dependent Casimir energy can be $10^4$ times larger than other mechanisms known to stabilize
quantum Hall stripes. This finding convincingly implies that our setting may be realized with currently available experimental technology. Having demonstrated that the Casimir energy can be used to stabilize fluctuating nematic order, we close by discussing the implications for recent terahertz cavity experiments on
quantum Hall stripes, as well as pave the road towards broader Casimir control of competing correlated electronic phases.
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All authors Ola Carlsson, Sambuddha Chattopadhyay, Jonathan B. Curtis, Frieder Lindel, Lorenzo Graziotto, Jérôme Faist, Eugene Demler
Statistical Mechanics · Cross-listed from quant-ph
The role of entropy production and thermodynamic uncertainty relations in the asymmetric thermalization of open quantum systems
Álvaro Tejero
The asymmetry between heating and cooling in open
quantum systems is a hallmark of nonequilibrium dynamics, yet its thermodynamic origin has remained unclear. Here, we investigate the thermalization of a
quantum system weakly coupled to a thermal bath, focusing on the
entropy production rate and the
quantum thermokinetic uncertainty relation (TKUR). We derive an analytical expression for the
entropy production rate, showing that heating begins with a higher
entropy production, which drives faster thermalization than cooling. The
quantum TKUR links this asymmetry to heat-current fluctuations, demonstrating that larger
entropy production suppresses fluctuations, making heating more stable than cooling. Our results reveal the thermodynamic basis of asymmetric thermalization and highlight uncertainty relations as key to nonequilibrium
quantum dynamics.
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Statistical Mechanics
Field-Theoretic Simulation of Dean-Kawasaki Dynamics for Interacting Particles
Jaehyeok Jin, Chen Liu and David R. Reichman
The formulation of a fluctuating hydrodynamic theory for interacting particles is a crucial step in the theoretical description of
liquids. The microscopic mappings proposed decades ago by Dean and Kawasaki have played a central role in the analytical treatment of such problems. However, the singular mathematical nature of the density distributions used in these derivations raises concerns about the validity and practical utility of the resulting
stochastic partial differential equations, particularly for direct numerical simulations. Recent efforts have centered on establishing a rigorous coarse-graining procedure to regularize the effective Dean-Kawasaki equation. Building on this foundation, we numerically investigate weakly interacting fluids within such a regularized framework for the first time. Our work reveals, at the level of structural correlations, the effects of regularization on the Dean-Kawasaki formalism and paves the way for improved numerical approaches to simulate fluctuating hydrodynamics in
liquids.
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Materials Science
Role of chromium oxides and carbides in strengthening CoCrFeNi multi-principle element alloys
Artur Olejarz, Wenyi Huo, Anna Kosinska et al. (+7 more)
Multi-principal element
alloys (MPEAs) can potentially offer exceptional material properties, but their complex, costly manufacturing limits their scalability. Chemical complexity and complex manufacturing processes lead to the formation of some secondary phases, which have a significant impact on the final properties. In this work, chromium compound dispersoid enhancements (Cr-
oxides and carbides) were formed in CoCrFeNi MPEAs to enhance their microstructural and high-temperature mechanical properties. A single FCC phase was observed in the arc melted (AM) samples, chromium
oxides were detected in the gas-atomized (GA) samples, and Cr2O3 with Cr23C6 or Cr7C3 was found in the mechanically alloyed (MA)samples depending on the sintering temperature. Mechanical tests at room temperature and 575{\deg}C, where no phase
evolution is expected, showed that the GA samples with
oxides achieved enhanced mechanical properties at 575{\deg}C. This was co-induced by precipitation strengthening, recrystallization suppression, and twinning-induced plasticity. The MA samples with carbides exhibited high strength but low ductility, with Cr7C3 outperforming Cr23C6 because of its lower hardness and twinning effects. This work links chromium compound
evolution to mechanical performance of MPEAs, offering insights to optimize HEA production for high-temperature applications through controlled phase formation.
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All authors Artur Olejarz, Wenyi Huo, Anna Kosinska, Maciej Zielinski, Tomasz Stasiak, Marcin Chmielewski, Wojciech Chmurzynski, Max Rae Chu, Michael Patrick Short, Lukasz Kurpaska
Materials Science
Comparing fine-tuning strategies of MACE machine learning force field for modeling Li-ion diffusion in LiF for batteries
Nada Alghamdi, Paolo de Angelis, Pietro Asinari et al. (+1 more)
Machine learning force fields (MLFFs) are transforming materials science and engineering by enabling the study of complex phenomena, such as those critical to battery operation. In this work, we explore the predictive capabilities of pre-trained and fine-tuned MACE MLFF and compare different fine-tuning strategies for predicting interstitial lithium diffusivity in LiF, a key component in the solid electrolyte interphase in Li-ion batteries. Our results demonstrate that the MACE-MPA-0 foundational model achieves comparable accuracy to well-trained DeePMD, in predicting key
diffusion properties based on large scale molecular dynamics simulation, while requiring minimal or no training data. For instance, the MACE-MPA-0 predicts an activation energy $E_a$ of 0.22eV, the fine-tuned model with only 300 data points predicts $E_a =$ 0.20eV, both of which show good agreement with the DeePMD model reference value of $E_a = $ 0.24eV. In this work, we provide a solid test case where fine-tuning approaches, whether using data generated for DeePMD or data produced by the foundational MACE model itself, yield similar robust performance to the DeePMD potential trained with over 40,000 actively learned data, albeit requiring only a fraction of the training data.
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All authors Nada Alghamdi, Paolo de Angelis, Pietro Asinari, Eliodoro Chiavazzo
Strongly Correlated Electrons
Emergent Electronic Flat Bands Through Dislocation Defect Phase Patterning: Effective One-Dimensional Model
Aziz Fall and Kaushik Dayal
Recent theoretical work has predicted that dislocation patterning induces anisotropic flat bands in the electronic band diagram, which can lead to unusual effects such as unconventional superconductivity. This work develops a reduced-dimensional framework to provide insights into their origin. An effective one-dimensional dislocation potential is constructed by averaging over the spatial distributions of dislocations along a singular direction. The resulting model introduces a parameter that quantifies the strain modulation, thereby providing a transparent approach to analyze the role of dislocation strain in leading to flat band formation.
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Strongly Correlated Electrons
Controlling an altermagnetic spin density wave in the kagome magnet CsCr3Sb5
Zihao Huang, Chenchao Xu, Yande Que et al. (+8 more)
The interplay of charge and
spin orders lies at the heart of correlated electron physics and plays a critical role in the emergence of unconventional
quantum phases. Kagome magnets provide a particularly promising platform to investigate these phenomena, owing to their geometrically frustrated
lattice structure. However, resolving
spin and charge orders microscopically and establishing ways to control them remain fundamental challenges. Here, we demonstrate
magnetic field control of an altermagnetic
spin density wave order intertwined with charge density wave order in kagome magnet CsCr3Sb5. Scanning tunneling microscopy down to deep cryogenic temperature of 50 mK reveals two previously unreported charge density wave orders in the Sb surface. Density functional theory confirms that one of them is coupled to a
spin density wave with an altermagnetic ground state. The charge density waves can be tuned in both amplitude and phase by an external
magnetic field, reflected in domain switching and stripe sliding of the charge density wave. Our findings deepen the understanding of
symmetry-breaking in kagome systems, providing a tunable platform to explore the interplay of electronic correlation with emergent
quantum magnetism.
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All authors Zihao Huang, Chenchao Xu, Yande Que, Yi Liu, Ranjith Shivajirao, Zheng Jue Tong, Amit Kumar, Chao Cao, Guang-Han Cao, Hong-Jun Gao, Bent Weber
Mesoscale and Nanoscale Physics
Fermionic influence superoperator for transport through Majorana zero modes
Jia-Lin Pan, Zi-Fan Zhu, Shixuan Chen et al. (+2 more)
In recent years, the study of Majorana signatures in
quantum transport has become a central focus in condensed matter physics. Here, we present a rigorous and systematic derivation of the fermionic superoperator describing the open
quantum dynamics of electron transport through Majorana zero modes, building on the techniques introduced in Phys. Rev. B 105, 035121 (2022). The numerical implementation of this superoperator is to construct its differential equivalence, the hierarchical equations of motion (HEOM). The HEOM approach describes the system-bath correlated dynamics. Furthermore, we also develop a functional derivative scheme that provides exact expressions for the transport observables in terms of the auxiliary density operators introduced in the HEOM formulation. The superoperator formalism establishes a solid theoretical foundation for analyzing key transport signatures that may uncover the unique characteristics of Majorana physics in mesoscopic systems.
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All authors Jia-Lin Pan, Zi-Fan Zhu, Shixuan Chen, Yu Su, Yao Wang
Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Surface Acoustic Wave Gas Sensors: Innovations in Functional Materials, Sensing Dynamics, and Signal Analysis
Suman Acharya, Balasubramanian Srinivasan, David Shanahan et al. (+3 more)
Surface Acoustic Wave gas sensors have garnered increasing
attention as highly sensitive, miniaturized, and wireless compatible platforms for molecular detection. Their unique ability to convert surface perturbations into measurable acoustic shifts makes them ideal for gas sensing across diverse environments. This review synthesizes reported SAW platforms across substrates and modes Rayleigh, SH-SAW, Love links transduction pathways to material choice, and
benchmarks performance for key analytes, e.g., NO2, NH3, VOCs, CO2, etc. We catalogue nanostructured
oxides,
polymers, carbon based films, and hybrid heterojunction coatings, highlighting attributes such as porosity, surface chemistry, and interfacial charge transfer that govern sensitivity and reversibility. We also highlight the emerging use of SAW devices to probe adsorption desorption dynamics, offering analyte specific interaction signatures beyond
equilibrium, offering a new perspective into analyte specific interaction pathways. Additionally, the integration of machine learning is discussed as a transformative tool for signal decoding, environmental compensation, and adaptive calibration. We also identify key challenges, cross sensitivity, signal drift, material degradation, and deployment at the edge and review recent strategies to address them. Looking ahead, we envision the
evolution of SAW platforms into intelligent, autonomous sensing systems with applications in environmental monitoring, industrial process control, and healthcare diagnostics.
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All authors Suman Acharya, Balasubramanian Srinivasan, David Shanahan, Utz Roedig, Alan O Riordan, Veda Sandeep Nagaraja
Strongly Correlated Electrons
The two conduction bands of monolayer CrSBr on Au
Yogal Prasad Ghimirey, Laxman Nagireddy, Cephise Cacho et al. (+2 more)
We report the electronic structure of monolayer CrSBr exfoliated onto mica template-stripped gold substrates. Angle-resolved photoemission spectroscopy reveals charge transfer from the substrate, populating the conduction band of monolayer CrSBr, accompanied by a pronounced reduction in the quasiparticle band gap. Furthermore, we observe two separate conduction bands that exhibit a splitting at the X point. This indicates a breaking of glide-mirror
symmetry, which in the bulk or in a free-standing monolayer protects the band degeneracies at the Brillouin zone boundary. Our results demonstrate that ultraflat gold substrates do more than modify carrier densities and screening: they can lift
symmetry-protected degeneracies and thus fundamentally reshape the band
topology of 2D materials.
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All authors Yogal Prasad Ghimirey, Laxman Nagireddy, Cephise Cacho, Neil R. Wilson, Matthew D. Watson
Materials Science
Atomistic Insights into the Degradation of Metal Phthalocyanine Catalysts during Oxygen Reduction Reaction
Huanhuan Yang and Guangfu Luo
Oxygen reduction catalysts frequently suffer from degradation under harsh operating conditions, and the limited understanding of the underlying mechanisms hampers the development of effective mitigation strategies. In this study, we integrate first-principles calculations with a time-dependent microkinetic model to investigate the deactivation pathways of six highly active metal phthalocyanines (MPc, M = Cr, Mn, Fe, Ru, Rh, and Ir) during the oxygen reduction reaction (ORR). We quantitatively assess the ORR processes, hydrogen peroxide generation, radical generation, and three primary degradation mechanisms, namely carbon oxidation, nitrogen protonation, and demetallation, through a reaction network involving 40 chemical species and 75 elementary reactions. Our findings reveal that the dominant degradation mechanism varies significantly across the MPcs. Under typical alkaline conditions, the primary byproducts arise from carbon oxidation, driven by .OH radical attack and structural reorganization of surface adsorbates, and from protonation at either the metal center or nitrogen sites. In the kinetics-controlled region, the ORR activity follows the order of RhPc > IrPc > FePc > MnPc > RuPc > CrPc. Notably, RhPc and IrPc demonstrate both higher ORR activity and greater stability than the widely studied FePc under elevated potentials.
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Strongly Correlated Electrons
Variational optimization of projected entangled-pair states on the triangular lattice
Jan Naumann, Jens Eisert and Philipp Schmoll
We introduce a general corner transfer
matrix renormalization group
algorithm tailored to projected entangled-pair states on the triangular
lattice. By integrating automatic differentiation, our approach enables direct variational energy minimization on this
lattice geometry. In contrast to conventional approaches that map the triangular
lattice onto a square
lattice with diagonal next-nearest-neighbour interactions, our native formulation yields improved variational results at the same bond dimension. This improvement stems from a more faithful and physically informed representation of the
entanglement structure in the tensor network and an increased number of variational parameters. We apply our method to the
antiferromagnetic nearest-neighbour Heisenberg model on the triangular and kagome
lattice, and
benchmark our results against previous numerical studies.
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Soft Condensed Matter
Effect of ice nucleating proteins on the structure-property relationships of ice: A molecular dynamics study
A. K. Shargh, C. D. Stiles and J. A. El-Awady
Ice-nucleating
proteins (INPs) are a unique class of biological macromolecules that catalyze the freezing of supercooled water far more efficiently than homogeneous nucleation. Their remarkable efficiency has motivated applications across diverse sectors, including agricultural frost protection, food processing and packaging, biomedical cryopreservation, and even strategies for mitigating glacier ice loss. The ice-nucleation performance of INPs and the mechanical behavior of the ice they produce depend strongly on their structural and biochemical characteristics. However, the links between INP properties, the resulting ice microstructure, and their mechanical behavior have yet to be systematically established. In this study, coarse-grained molecular dynamics (CGMD) simulations using the machine-learned ML-BOP potential are employed to investigate how varying INP densities influence the ice nucleation temperature, the resulting ice microstructure, and the mechanical behavior of the formed ice under creep tensile loading. We find that, depending on their density, INPs can significantly raise the ice nucleation rate while altering the grain structure of ice. Our simulations reveal that INP-assisted nucleation leads to faster stabilization of the resulting polycrystalline ice composed of hexagonal ice (ice Ih) and cubic ice (ice Ic) as compared to nucleation in pure water. Moreover, higher INP densities and smaller ice grain sizes reduce the overall yield stress, while promoting
diffusion-accommodated grain boundary sliding creep. These findings provide molecular-level insight into how INPs influence both the nucleation process and the mechanical behavior of ice, highlighting a pathway to engineer ice with tailored stability for real-world settings, including human activities and infrastructure in polar and icy environments.
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Soft Condensed Matter
A network-based approach to measure granule size distribution for discrete element modeling of granulation
Shubham Jain, Anurag Tripathi, Jayanta Chakraborty et al. (+1 more)
Drum granulation is a size enlargement process where granular material is agitated with a
liquid binder to form larger size granules. Discrete element modeling is increasingly being used to better understand and investigate the granulation process. However, unlike experiments the measurement of granule size within a DEM framework often necessitates an explicit quantitative definition of a granule and a corresponding granule identification method. In this work, we show that the existing definitions and the associated methods in literature are ineffective at identifying granules for dense flows such as during drum granulation. We propose an improved definition and granule identification method based on community-detection used in network science literature. The proposed method better identifies granules in a drum granulator as benchmarked against
liquid-settling. We also vary granulation process parameters like
liquid content and fill level and study their effect on the cumulative granule size distribution attained after drum granulation. We find that the existing granule-identification methods fail to reproduce the well-known effects of process parameters on the cumulative granule size distribution. The proposed method, based on community detection, reproduces the effects with better accuracy.
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All authors Shubham Jain, Anurag Tripathi, Jayanta Chakraborty, Jitendra Kumar
Statistical Mechanics · Cross-listed from quant-ph
Information-thermodynamic bounds on precision in interacting quantum systems
Ryotaro Honma and Tan Van Vu
The thermodynamic uncertainty relation quantifies a trade-off between the relative fluctuations of trajectory currents and the thermodynamic cost, indicating that the current precision is fundamentally constrained by
entropy production. In classical bipartite systems, it has been shown that information flow between subsystems can enhance the current precision alongside thermodynamic dissipation. In this study, we investigate how information flow, local dissipation, and
quantum effects jointly constrain current fluctuations within a subsystem of interacting
quantum systems. Unlike classical bipartite systems,
quantum subsystems can exhibit simultaneous state changes and maintain
quantum coherence, which fundamentally alters the precision-dissipation trade-off. For this general setting, we derive a
quantum thermokinetic uncertainty relation for interacting multipartite systems, establishing a thermodynamic trade-off between current fluctuations, information flow, local dissipation, and
quantum effects. Our analysis shows that, in addition to local dissipation, both information exchange and
quantum coherence play essential roles in suppressing current fluctuations. These results have important implications for the performance of
quantum thermal machines, such as information-thermodynamic engines and
quantum clocks. We validate our theoretical findings through numerical simulations on two representative models: an autonomous
quantum Maxwell's demon and a
quantum clock. These results extend uncertainty relations to multipartite open
quantum systems and elucidate the functional role of information flow in fluctuation suppression.
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Strongly Correlated Electrons
Dynamical moment fragmentation in the all-in all-out pyrochlore Nd2Sn2O7
Yi Luo, Matthew S. Powell, Joseph A. M. Paddison et al. (+4 more)
We report single-
crystal neutron spectroscopy and bulk characterization on hydrothermally grown Nd2Sn2O7, revealing a dynamical moment fragmentation embedded within the all-in-all-out ordered state. The spectra show a nearly flat band with pinch-point-like momentum dependence, accompanied by dispersive branches that generate half-moon features across multiple Brillouin zones. These defining signatures are captured quantitatively by a minimal dipolar-octupolar
spin Hamiltonian, demonstrating excellent agreement between experiment and theory. The higher flat-mode energy helps account for the absence of dynamical interference in prior
muon spin relaxation (muSR) studies, while the lack of any
photon-like excitation imposes strict constraints on the proposed Coulombic antiferromagnet scenario. Our results extend dynamical moment fragmentation to Nd2Sn2O7 and identify it as a clean, tractable platform for quantitative exploration of emergent gauge-field physics and multipolar
spin-wave dynamics in frustrated magnets.
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All authors Yi Luo, Matthew S. Powell, Joseph A. M. Paddison, Brenden R. Ortiz, J. Ross Stewart, Joseph W. Kolis, Adam A. Aczel
Materials Science
Investigating Anharmonicities in Polarization-Orientation Raman Spectra of Acene Crystals with Machine Learning
Paolo Lazzaroni, Shubham Sharma and Mariana Rossi
We present a first-principles machine-learning computational framework to investigate anharmonic effects in polarization-orientation (PO) Raman spectra of molecular
crystals, focusing on anthracene and naphthalene. By combining machine learning models for interatomic potentials and polarizability tensors, we enable efficient, large-scale simulations that capture temperature-dependent vibrational dynamics beyond the harmonic approximation. Our approach reproduces key qualitative features observed experimentally. We show, systematically, what are the fingerprints of anharmonic
lattice dynamics, thermal expansion, and Raman tensor
symmetries on PO-Raman intensities. However, we find that the simulated polarization dependence of Raman intensities shows only subtle deviations from quasi-harmonic predictions, failing to capture the pronounced temperature-dependent changes that have been reported experimentally in anthracene. We propose that part of these inconsistencies stem from the impossibility to deconvolute certain vibrational peaks when only experimental data is available. This work therefore provides a foundation to improve the interpretation of PO-Raman experiments in complex molecular
crystals with the aid of theoretical simulations.
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Superconductivity
Anyon Bound States and Hybrid Superconductivity
Paul Leask
The interactions of anyonic quasi-particles (
vortices) in the Chern–Simons extension of the Ginzburg–Landau model is investigated and we show that it manifestly realizes a hybridization of type I/II superconductivity. Through Gauss' law, each
vortex simultaneously carries a flux
quantum and a proportional Noether charge, thereby realizing an anyonic excitation. The Chern–Simons coupling also modifies the screening structure of the gauge fields, producing complex-conjugate masses that yield a common penetration depth with an oscillatory phase. This altered asymptotic behavior breaks the conventional type-I/type-II dichotomy of the Ginzburg–Landau model. As a result,
vortex anyons experience short-range repulsion and long-range attraction, enabling the formation of separated multi-
vortex bound states with non-monotonic interaction energy.
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Strongly Correlated Electrons
Probing frustrated metallo-molecular spin Kondo lattice interfaces through anomalous Nernst effect
Servet Ozdemir, Matthew Rogers, Conor J. McCluskey et al. (+7 more)
Frustrated Kondo
spin lattice (KSL) systems away from the
antiferromagnetic (AFM) ground state have been found to display strange metal behaviour. A signature of strange metals in correlated systems is large Nernst response. Metallo-molecular interfaces of supramolecular
lattices have been demonstrated as 2D KSL systems in STM studies. Here going beyond STM experiments we report a frustrated AFM state on molecular interfaces of Pt(111) and Pt(111)/Co films with around room temperature
spin freezing transitions. Near these transitions we measure an anomalous Nernst coefficient of at least 3 $\mu$V/K.
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All authors Servet Ozdemir, Matthew Rogers, Conor J. McCluskey, Raymond G. McQuaid, Zachariah Parkin, Mannan Ali, Gavin Burnell, Joseph Barker, B J Hickey, Oscar Cespedes
Soft Condensed Matter
Geometric Mechanics of Thin Periodic Surfaces
Wenqian Sun, Yanxin Feng, Christian D. Santangelo et al. (+1 more)
Thin surfaces are ubiquitous in nature, from leaves to
cell membranes, and in technology, from paper to corrugated containers. Structural thinness imbues them with flexibility, the ability to easily bend under light loads, even as their much higher stretching stiffness can bear substantial stresses. When surfaces have periodic patterns of either smooth hills and valleys or sharp origami-like creases this can substantially modify their mechanical response. We show that for any such surface, there is a duality between the surface rotations of an isometric deformation and the in-plane stresses of a force-balanced configuration. This duality means that of the six possible combinations of global in-plane strain and out-of-plane bending, exactly three must be isometries. We show further that stressed configurations can be expressed in terms of both the applied deformation and the isometric deformation that is dual to the pattern of stress that arises. We identify constraints rooted in
symplectic geometry on the three isometries that a single surface can generate. This framework sheds new light on the fundamental limits of the mechanical response of thin periodic surfaces, while also highlighting the role that continuum differential geometry plays in even sharply creased origami surfaces.
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All authors Wenqian Sun, Yanxin Feng, Christian D. Santangelo, D. Zeb Rocklin
Strongly Correlated Electrons
Systematic cRPA study of two-dimensional MA$_2$Z$_4$ materials: From unconventional screening to correlation-driven instabilities
F. Bagherpour, Y. Yekta, H. Hadipour et al. (+5 more)
Understanding the interplay between screening, electronic correlations, and collective excitations is essential for the design of two-dimensional
quantum materials. Here, we present a comprehensive first-principles study of more than 60 MA$_2$Z$_4$ monolayers, encompassing semiconducting, metallic, cold-metallic,
magnetic, and topological phases. Using the constrained random phase approximation (cRPA), we compute material-specific effective Coulomb interaction parameters $U$, $U'$, and $J$, including their spatial dependence across distinct correlated subspaces defined by local coordination and
crystal symmetry. In semiconducting compounds, long-range nonlocal interactions persist, revealing unconventional screening and suggesting strong excitonic effects beyond simple dielectric models. In cold-metallic systems, sizable long-range Coulomb interactions remain despite the presence of free carriers, highlighting their atypical metallic screening. Among 33-valence-electron compounds, we find $U_{\mathrm{eff}} > W$ in the $\beta_2$ phase, indicating proximity to charge-density-wave or Mott instabilities. Several V- and Nb-based systems exhibit intermediate-to-strong correlation strength, with $U/W > 1 $ in multiple cases. Using cRPA-derived Stoner parameters, we identify
magnetic instabilities in various V-, Nb-, Cr-, and Mn-based compounds. Finally, selected cold-metallic systems display plasmon dispersions that deviate from the conventional $\sqrt{q}$ behavior, revealing nearly non-dispersive low-energy modes. These results position MA$_2$Z$_4$ monolayers as a versatile platform for investigating correlation-driven instabilities and emergent collective behavior in two dimensions.
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All authors F. Bagherpour, Y. Yekta, H. Hadipour, E. Sasioglu, A. Khademi, S. A. Jafari, I. Mertig, S. Lounis
Strongly Correlated Electrons · Cross-listed from physics.chem-ph
Mixed-precision ab initio tensor network state methods adapted for NVIDIA Blackwell technology via emulated FP64 arithmetic
Cole Brower, Samuel Rodriguez Bernabeu, Jeff Hammond et al. (+5 more)
We report cutting-edge performance results via mixed-precision
spin adapted ab initio Density
Matrix Renormalization Group (DMRG) electronic structure calculations utilizing the Ozaki scheme for emulating FP64 arithmetic through the use of fixed-point compute resources. By approximating the underlying
matrix and tensor
algebra with operations on a modest number of fixed-point representatives (“slices”), we demonstrate on smaller
benchmark systems and for the active compounds of the FeMoco and cytochrome P450 (CYP) enzymes with complete active space (CAS) sizes of up to 113 electrons in 76 orbitals [CAS(113, 76)] and 63 electrons in 58 orbitals [CAS(63, 58)], respectively, that the chemical accuracy can be reached with mixed-precision arithmetic. We also show that, due to its variational nature, DMRG provides an ideal tool to
benchmark accuracy domains, as well as the performance of new hardware developments and related numerical libraries. Detailed numerical error analysis and performance assessment are also presented for subcomponents of the DMRG
algebra by systematically interpolating between double- and pseudo-half-precision. Our analyis represents the first
quantum chemistry evaluation of FP64 emulation for correlated calculations capable of achieving chemical accuracy and emulation based on fixed-point arithmetic, and it paves the way for the utilization of state-of-the-art Blackwell technology in tree-like tensor network state electronic structure calculations, opening new research directions in materials sciences and beyond.
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All authors Cole Brower, Samuel Rodriguez Bernabeu, Jeff Hammond, John Gunnels, Sotiris S. Xanthea, Martin Ganahl, Andor Menczer, Örs Legeza
Strongly Correlated Electrons
Refined spin Hamiltonian on the Cairo pentagonal lattice of Bi2Fe4O9
Emma Y. Lenander, Frida B. Nielsen, Jakob Lass et al. (+14 more)
The frustrated magnet Bi2Fe4O9 has been reported to exhibit complex
spin dynamics coexisting with conventional
spin wave excitations. The
magnetic Fe3+ (S = 5/2) ions are arranged into a distorted two-dimensional Cairo pentagonal
lattice with weak couplings between the layers, developing long-ranged non-collinear
antiferromagnetic order below 245 K. In order to enable studies and modelling of the complex dynamics close to TN, we have reexamined the
magnetic excitations across the complete energy scale (0 < E < 90 meV) at 10 K. We discover two distinct gaps, which can be explained by introducing, respectively, easy axis and easy plane anisotropy on the two unequivalent Fe-sites. We develop a refined
spin Hamiltonian that accurately accounts for the dispersion of essentially all
spin-wave branches across the full spectral range, except around 40 meV, where a splitting and dispersion are observed. We propose that this mode is derived from
phonon hybridization. Polarisation analysis shows that the system has
magnetic anisotropic fluctuations, consistent with our model. A continuum of scattering is observed above the
spin wave branches and is found to principally be explained by an instrumental resolution effect. The full experimental mapping of the excitation spectrum and the refined
spin Hamiltonian provides a foundation for future quantitative studies of
spin waves coexisting with unconventional
magnetic fluctuations in this frustrated magnet found at higher temperatures.
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All authors Emma Y. Lenander, Frida B. Nielsen, Jakob Lass, Ursula B. Hansen, Kristine M. L. Krighaar, Asbjørn Preuss, Tobias Weber, Mechthild Enderle, Henrik Jacobsen, Uwe Stuhr, Ryoichi Kajimoto, Mitsutaka Nakamura, Manfred Burianek, Andrea Kirsch, Henrik M. Rønnow, Kim Lefmann, Pascale P. Deen