Strongly Correlated Electrons · Cross-listed from math-ph
The Classification of Pauli Stabilizer Codes: A Lattice and Continuum Treatise
Bowen Yang and Matthew Yu
We classify mobile Pauli stabilizer codes up to gapped interfaces and coarse-graining using the framework of algebraic $\mathrm{L}$-theory. We compare this classification with that of framed TQFTs, theories that arise naturally in the continuum, highlighting a close structural relationship between the two. Our approach is formulated in the category of perfect chain complexes equipped with quadratic functor over the Laurent
polynomial ring $R = \mathbb{Z}/p[x_1^{\pm 1}, \ldots, x_n^{\pm 1}]$, within which the collection of topological operators of Pauli stabilizer codes arise naturally as objects. In particular, we establish a bulk-boundary correspondence for
lattice theories: the equivalence class of a Pauli stabilizer code up to gapped interface is described by a Clifford QCA in one dimension higher. This is done using the universal target category for stabilizer codes, which is the categorical spectrum whose existence and universal properties are introduced in this work. We conclude by highlighting subtle differences between the classification of Pauli stabilizer codes and TQFTs, leading to qualitative distinctions between
lattice and continuum theories.
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Strongly Correlated Electrons
Quantum Rotors on the Fuzzy Sphere and the Cubic CFT
Andreas Stergiou
The three-dimensional cubic conformal field theory governs the critical behaviour of Heisenberg magnets with cubic anisotropy. Studying this theory non-perturbatively is challenging, because its most easily accessible observables are numerically very close to those of the more symmetric $O(3)$ model. In this work, we overcome this difficulty using the fuzzy sphere regularisation method. By adding a cubic-invariant two-body interaction to the
quantum rotor
Hamiltonian used for the $O(3)$ model, we break the continuous rotational
symmetry by construction and unambiguously isolate the cubic critical point. Using exact diagonalisation and the density
matrix renormalisation group, we calculate the scaling dimensions of several key operators, including the leading scalar singlets, and resolve the splitting of the $O(3)$ rank-two traceless symmetric tensor into the $E_g$ and $T_{2g}$ representations of the cubic group. Our results are consistent with existing Monte Carlo, conformal perturbation theory, and $\varepsilon$ expansion
benchmarks, demonstrating the power of the fuzzy sphere in resolving closely spaced universality classes.
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Quantum Gases · Cross-listed from physics.hist-ph
The Legacy of Enrico Fermi to Varenna
Vladislav Gavryusev and Massimo Inguscio
The Varenna school is a hub where generations of physicists, including numerous Nobel laureates, have shaped the field, often through collaborative exchanges across political and cultural boundaries. We examine the scientific legacy of Enrico
Fermi and its influence on modern atomic, molecular, and optical physics. Beginning with
Fermi's 1954 lectures at the Varenna school, key developments are traced from high-energy physics to
laser spectroscopy, precision metrology, and the control of ultracold atoms. Milestones such as Doppler-free spectroscopy, optical frequency combs, Bose-Einstein condensation, and degenerate
Fermi gases are highlighted as turning points leading to
quantum simulation and
quantum computation.
Fermi's early advocacy for building a computer, rather than buying it, can be viewed as a precursor to today's efforts in
quantum science and technologies. This historical trajectory and legacy continues to inform current research in
quantum matter and information science.
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Materials Science
Trillion-atom molecular dynamics simulations with ab initio accuracy
Pengfei Suo, Wudi Cao, Xingxing Wu et al. (+14 more)
Material properties are fundamentally dictated by multiscale phenomena, which often reach mesoscale in size. The {\mu}m mesoscale is also the size which can be observed directly under an optical microscope, bridging the atomistic microscopic description with the continuous model macroscopic world. In this work, we report an unprecedented molecular dynamics (MD) simulation comprising 1.62 trillion atoms. Utilizing the neuroevolution potential (NEP) framework, we attained ab initio accuracy on China's New-generation Intelligent Supercomputer. Our implementation achieves a time-to-solution (s/step/atom) 100 times faster than previous state-of-the-art machine learning force field simulations, and 1,000 times faster than the Gordon Bell Prize-winning application from six years ago. Furthermore, we demonstrate an 86.9% weak scaling efficiency from a single GPGPU to 45,000 GPGPUs. These results redefine atomistic simulation boundaries, enabling direct mesoscopic modeling with
quantum-level precision.
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All authors Pengfei Suo, Wudi Cao, Xingxing Wu, Wenjie Zhang, Zheyong Fan, Shuanghan Xian, Rui Wang, Cheng Qian, Chao Liang, Qinghong Yuan, Xiaoshuang Chen, Pengfei Guan, Jingde Bu, Hongzhen Tian, Yanjing Su, Feng Ding, Lin-Wang Wang
Statistical Mechanics
Thermoinformational State Construction: Generative Energies, Entropies, and H-Theorem Consistency
George-Rafael Domenikos, Lock Yue Chew and Victoria Leong
We introduce a constructive framework for assigning thermodynamic structure to an arbitrary data system from its measured microstates. Starting from an empirical distribution over configurations, we first infer a data-driven energy function by fitting a Boltzmann-type model to the observed statistics, thereby defining an energy axis that is intrinsic to the system. We then push the empirical distribution onto this energy coordinate and pose an inverse maximum-
entropy problem: we learn a strictly concave trace-form
entropy functional whose maximizer, under a small set of constraints extracted from the data, reproduces the observed energy-space histogram. With energy and
entropy defined in this coupled, system-specific manner, macroscopic variables such as internal energy, an
entropy-energy relation S(U), and a thermoinformational temperature T^(-1)= dS/dU follow consistently along admissible families of states. We demonstrate the construction on canonical unimodal and
multimodal examples, including a harmonic well (recovering the classical
equilibrium limit up to gauge) and a bistable double-well where global-constraint MaxEnt surrogates can obscure barrier and coexistence structure. The resulting formulation provides a principled route from microstate data to thermodynamically consistent macroscopic descriptors, with an optimized
entropy matched to the empirical system.
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Statistical Mechanics · Cross-listed from quant-ph
Contracting Tensor Networks with Generalized Belief Propagation
Joseph Tindall, Grace M. Sommers and Hilbert Kappen
Recent years have seen a growing interest in the use of belief propagation - an
algorithm originally introduced for performing statistical inference on graphical models - for approximate, but highly efficient, tensor network contraction. Here, we detail how to apply generalized belief propagation (GBP) - where messages are passed within a hierarchy of overlapping regions of the tensor network - to approximately contract tensor networks and obtain accurate results. The original belief propagation
algorithm is a corner case of this approach, corresponding to a particularly simple choice of regions of the tensor network. We implement the GBP
algorithm for a number of different region choices on a range of two- and three-dimensional, infinite and finite tensor networks, solving the corresponding fixed point equations both numerically and, in certain tractable cases, analytically. Our examples include calculating the partition function of the fully frustrated Ising model, computing the ground state degeneracy of three-dimensional ice models, measuring observables on the deformed AKLT
quantum state and evaluating the norm of randomly generated tensor network states.
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Strongly Correlated Electrons
Non-Abelian Particle-Loop, Fracton, and Planon Condensation in Cage-Net Models
Yifei Wang, Yu Zhao, Yingcheng Li et al. (+2 more)
We present a framework for non-Abelian p-loop, fracton, and planon condensation in 3+1 dimensions by constructing extended cage-net fracton models using decoupled layers of the Hu-Geer-Wu (HGW) string-net model. These cage-net models extend the conventional cage-net models based on the Levin-Wen (LW) string-net model in the sense that they inherit the tail degrees of freedom of the HGW models, which are essential for completely describing the internal spaces of quasiparticles. This approach allows us to explicitly derive the quasiparticle spectra of the cage-net models by projecting those of the parent 2D HGW layers. Utilizing this framework, we can condense the p-loops formed by non-Abelian anyons within a fracton phase. Specifically, we construct the condensation projector for $(\sigma\bar{\sigma}, 1)$-loops within the extended Ising Cage-Net (ICN) model. We demonstrate that condensing these non-Abelian loops drives a phase transition that maps the ICN model to the X-cube (XC) model defined on a truncated cubic
lattice, a process that explicitly reveals the splitting of non-Abelian planons into distinct sub-dimensional excitations. Furthermore, our framework extends to the condensation of fractons and planons: we demonstrate that in the ICN model fracton condensation drives the decoupling of the 3D fracton order back into isolated 2D topological order layers, while planon condensation collapses the system entirely into a trivial phase. Our results establish a concrete
Hamiltonian mechanism for phase transitions between distinct fracton orders and provide a generalizable method for analyzing the
evolution of sub-dimensional excitations.
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All authors Yifei Wang, Yu Zhao, Yingcheng Li, Hao Song, Yidun Wan
Quantum Gases
Dynamical preparation of U(1) quantum spin liquids in an analogue quantum simulator
Simon Karch, Melissa Will, Irene Prieto Rodriguez et al. (+7 more)
Locally constrained gauge theories underpin our understanding of fundamental interactions in particle physics and the emergent behaviour of
quantum materials. In strongly correlated systems, they can give rise to
quantum spin liquids that lack conventional order and are defined by coherent superpositions of an extensive number of many-body configurations. Realising and probing such exotic states experimentally is an outstanding challenge both in solid-state and synthetic
quantum systems, not least due to the difficulty of detecting the fragile coherences between many-body states. Here, we report a large-scale (>3,000 sites) realisation of a two-dimensional U(1)
lattice gauge theory with ultracold atoms in a square optical superlattice and demonstrate non-
equilibrium preparation of extended regions of U(1)
quantum spin liquids. We demonstrate Gauss's law validity in a quench experiment, enabled by a new microscopy technique for detecting doubly occupied sites. We observe characteristic real-space correlations and momentum-space pinch points, hallmarks of the emergent U(1) gauge structure. Using round-trip interferometric protocols, we directly observe large-scale coherence between many-body configurations, providing strong evidence for
quantum spin liquid regions extending over ~100
lattice sites. Our results establish non-
equilibrium quantum simulation protocols as a powerful route for accessing and probing exotic, highly-entangled states beyond those hosted by the engineered
Hamiltonian in thermal
equilibrium.
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All authors Simon Karch, Melissa Will, Irene Prieto Rodriguez, Nikolas Liebster, SeungJung Huh, Michael Knap, Frank Pollmann, Clemens Kuhlenkamp, Immanuel Bloch, Monika Aidelsburger
Statistical Mechanics
Universal tracer statistics in single-file transport
Soumyabrata Saha, Jitendra Kethepalli, Benjamin Guiselin et al. (+2 more)
We uncover an emergent universality in the large-scale, long-time statistics of a one-dimensional hard-rod gas evolving under two fundamentally different classes of microscopic dynamics:
stochastic (diffusive) and
unitary (ballistic). Remarkably, despite the difference of the two systems, the one-time joint distribution of the positions of multiple tracers exhibits identical non-Gaussian fluctuations, up to a simple dynamical scaling. This universality holds in both annealed and quenched ensembles, demonstrating a persistent
memory of the initial state. Differences between the dynamics manifest at large scales only in multi-time statistics. Our conclusions are based on explicit large-deviation results for the one-time statistics of tracer pairs and the two-time statistics of a single tracer. Similar physics extends to current fluctuations, demonstrated explicitly in the quenched ensemble. We obtain these results from exact microscopic solutions for both dynamics and, independently, from fluctuating hydrodynamics in the ballistic case in the annealed ensemble. Our rare-event simulations further corroborate these findings and provide a novel demonstration of sampling atypical fluctuations in both types of hard-rod gas.
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All authors Soumyabrata Saha, Jitendra Kethepalli, Benjamin Guiselin, Jacopo De Nardis, Tridib Sadhu
Statistical Mechanics · Cross-listed from quant-ph
Experimental high-dimensional multi-qubit Bell non-locality on a superconducting quantum processor
Yousef Mafi, Ali G. Moghaddam and Teemu Ojanen
Combining recent advances in superconducting
quantum hardware, we explore
quantum correlations in a previously inaccessible regime by observing simultaneously high-dimensional and many-body Bell non-locality. We report a high-confidence Bell violation in the correlations between two $d=64$-dimensional systems encoded in twelve
qubits. For system sizes up to $d=32$, the strength of the observed nonlocal correlations exceeds the
quantum upper bound for $d=2$ systems, providing direct evidence of high-dimensional nonlocality. Furthermore, we demonstrate that the observed violation is genuinely collective: all
qubits contribute to the nonlocal correlations, while most pairwise correlations across the bipartition remain Bell-local. Our work illustrates how present-day
quantum processors enable the exploration of fundamental predictions of
quantum mechanics in previously inaccessible regimes and, in turn, how fundamental
quantum effects can be used to
benchmark their performance.
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Superconductivity
Nonintegral Flux Trapping in Frustrated Josephson Networks of Triplet Superconductors
Grayson R. Frazier, Colton Lelievre and Yi Li
In a Josephson junction network, anisotropic coupling between
spin triplet pairing correlations can lead to frustrated $d$ vector textures that support spontaneous Josephson currents and nonintegral flux trapping. Such networks can appear in superconducting polycrystals, as well as single-
crystal superconductors. In analogy to classical
spin systems, in which the presence of
geometric frustration and anisotropic superexchange can lead to nontrivial
spin textures, Josephson networks with anisotropic Josephson couplings cannot simultaneously optimize their $\mathrm{U}(1)$ superconducting phase difference and relative $d$ vector orientations. The internal pairing structure of Cooper pairs twists as they tunnel across the Josephson junction, and the $d$ vector texture enters as an emergent
geometric phase which can spontaneously trap fractional flux. For
unitary triplet pairing order, this mechanism can support $\pi$-flux trapping above a critical value of antisymmetric Josephson coupling, and is distinct from usual half-
quantum vortices. The results of this work reveal new routes to engineer frustrated Josephson networks from the interplay of
magnetic textures and
spin triplet superconducting pairing order.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Operating a contextual Stern-Gerlach apparatus
Th. K. Mavrogordatos
We propose a contextual cavity/
circuit QED analogue and extension of the Stern-Gerlach experiment, where the pseudo-
spin of a two-state `atomic' transition plays the role of the “
spin”, while the resonant field driving the transition stands for the “
magnetic field”. A phase-sensitive continuous detection of the cavity field coupled to the induced `atomic' dipole affects the stability of the two distinct outcomes. The dressed states comprising the latter give their place to a self-consistent spontaneous dressed-state polarization as the driving strength is lowered. The associated
evolution proves anew highly contextual, underpinned by a persistent production of coherent-state superpositions for a particular setting of the monitoring device. Finally, when bistability is absent, we employ the photoelectron `atomic' emission statistics as a diagnostic tool of the cavity field fluctuations.
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Quantum Gases
Floquet engineering of tight-binding Hamiltonians in momentum space lattices
D. Ronco, F. Arrouas, N. Ombredane et al. (+4 more)
Quantum simulation with ultracold atoms provides a versatile platform to emulate condensed-matter models. In particular, momentum-space
lattices enable the realization of programmable tight-binding
Hamiltonians. Here, we generalize this approach by exploiting
quantum resonances of a periodically driven (shaken) rotor within the Floquet framework. Using first-order time-dependent perturbation theory, we derive analytical relations between the
lattice modulation and the effective tight-binding parameters, and identify explicit solutions for several resonances. We further apply optimal-control techniques to enhance the multi-period Floquet fidelity and extend the accessible parameter regimes. Experimentally, we implement this scheme with a Bose-Einstein condensate of rubidium-87 atoms in a dynamically modulated optical
lattice. We demonstrate the simulation of the Rice-Mele model, including band-structure measurements and topological edge states, as well as momentum Bloch oscillations, and superlattice configurations with controlled periodicity. Our results establish
quantum resonances as a powerful resource for Floquet engineering of tight-binding models in momentum space.
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All authors D. Ronco, F. Arrouas, N. Ombredane, E. Flament, Q. Levoy, B. Peaudecerf, D. Guéry-Odelin
Mesoscale and Nanoscale Physics
Gate-dependent offset charge shifts and anharmonicity in gatemon qubits in the weak tunneling regime
Utkan Güngördü, Rusko Ruskov, Silas Hoffman et al. (+3 more)
Gatemon
qubits are based on a
superconductor-
quantum dot-
superconductor (S-QD-S) junction which enables in situ electrostatic tuning via a gate electrode. For a single-channel QD this structure gives rise to two subgap Andreev bound states (ABSs), and generally leads to a richer
quantum phase dynamics as compared to conventional transmons. In a recent work [Phys. Rev. B 111, 214503 (2025)] we derived the
quantum phase dynamics from a many-body treatment which leads to an effective gate voltage-dependent
Hamiltonian that self-consistently incorporates the phase quantization. It predicts (i) a renormalization of the junction's effective capacitance and (ii) the presence of gate voltage and occupation-dependent charge offsets in junctions with tunneling asymmetry. Here, we quantify the observable impact of these effects on the
qubit's energy spectrum and anharmonicity, by studying the interplay of the two Andreev branches as a function of dot-gate voltages and junction transparencies. We show the relation of these predictions to simplified gatemon models and propose a protocol to experimentally detect the predicted charge offsets.
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All authors Utkan Güngördü, Rusko Ruskov, Silas Hoffman, Kyle Serniak, Andrew J. Kerman, Charles Tahan
Soft Condensed Matter
Shear-driven mixing of segregated granular materials
Hugo N. Ulloa and Tomás Trewhela
As granular materials flow and settle, interactions among particles of different sizes or properties drive mixing and segregation, producing dynamics that shape systems ranging from silos to asteroids. A hallmark of polydisperse granular flows is shear-driven size segregation, in which larger grains tend to rise above smaller ones through particle-scale rearrangements. Despite substantial progress in modeling granular flow and segregation, the complementary process of granular mixing remains less well understood. Here, we investigate the
evolution of initially segregated dense granular materials driven out of
equilibrium by imposed shear. We ask: what controls the extent and rate of mixing and restratification in a sheared bidisperse granular flow? Addressing this question is essential for understanding how external forcing disrupts or reinforces particle-size organization, and for optimizing processes that require controlled mixing. Using theoretical analysis and numerical simulations, we develop a framework that quantifies the degree of mixing and segregation dynamics of dense bidisperse granular flows. Our results identify the controlling roles of particle-size ratio and the Péclet number, clarify the conditions under which segregated states persist or are transiently homogenized, and provide a basis for improved prediction and control of granular mixtures in natural and industrial settings.
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Strongly Correlated Electrons
Asliddin Khudoyberdiev, Dag-Björn Hering, Vanessa Sulaiman et al. (+1 more)
The switching of
antiferromagnetic order and its efficient control promise to enable ultrafast manipulation of data and large storage capacity. Recently, the time-dependent Schwinger
boson mean-field theory has been successfully developed to study the Néel vector switching in hypercubic
antiferromagnetic lattices. In the present article, we aim at demonstrating that the approach is a well-justified framework to capture the essentials of the switching process, even in low-
symmetry quantum antiferromagnets. To this end, we show the possibility of the sublattice magnetization reorientation in the
quantum antiferromagnetic honeycomb
lattice. First,
equilibrium properties of the honeycomb
lattice are analyzed using the Schwinger
boson mean-field theory and compared to the continuous similarity transformation method to justify the applicability of the approach. Then, the Schwinger
boson mean-field theory is employed for switching process. We provide a comprehensive answer to the question what the threshold switching fields are when the coordination number of the
lattice is varied. Indeed, the results of the study reveal a correspondence between
lattice structures and the threshold fields by comparing them for the square and the simple cubic
lattices and the honeycomb
lattice. The findings of the present article extend the foundation for future theoretical and computational advancements in the field of
antiferromagnetic switching. These advancements are of particular relevance for the development of ultrafast spintronic or magnonic devices.
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All authors Asliddin Khudoyberdiev, Dag-Björn Hering, Vanessa Sulaiman, Götz S. Uhrig
Mesoscale and Nanoscale Physics
Singlet-triplet oscillations in multivalley Si double quantum dots
Łukasz Cywiński, Mats Volmer, Tom Struck et al. (+2 more)
Charge separation from the $(4,0)$ to the $(3,1)$ state in a Si/SiGe double
quantum dot is commonly used for initialization of
spin qubits and Pauli-
spin-blockade readout. It was used in recent experiments involving creation of the $(3,1)$ singlet, and subsequent shuttling of one of the electrons. We present a theoretical description of the process of charge separation and singlet-triplet mixing, arriving at expressions for the singlet return probability that take into account experimentally observed finite probabilities of the creation of singlets with various patterns of valley occupations. In our analysis we focus on
magnetic fields for which the electron
spin Zeeman splitting is close to the valley splitting in one of the dots, when the
spin-valley coupling causes a strong renormalization of the frequency of oscillations of singlet return probability. The latter effect has been recently used to perform valley splitting mapping by shuttling of one
quantum dot to various locations with respect to the other. We give a detailed description of singlet-triplet dynamics near these
spin-valley resonances and compare the results of calculations with measurements on double
quantum dots in two distinct Si/SiGe
heterostructures. Comparison of theory with experiments in which the presence of a few valley occupation patterns is visible, gives insight into the valley dependence of $g$-factors in these structures, providing support for a recently proposed theoretical model of this dependence. We also discuss how dephasing of singlet return probability oscillations near the
spin-valley resonances is affected by valley splitting fluctuations caused by electric field noise.
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All authors Łukasz Cywiński, Mats Volmer, Tom Struck, Giordano Scappucci, Lars R. Schreiber
Statistical Mechanics
N. Johnson, D. Marenduzzo, A. Morozov et al. (+2 more)
We revisit the classical transfer
matrix solution of the one- and two-dimensional Ising model from the perspective of Clifford and conformal
geometric algebras. Building on Kaufman's spinor formulation, we show that all elements entering the solution, including the transfer
matrix, its eigenvectors, and the quasiparticle excitations, admit a natural and unified interpretation as elements of an appropriate conformal Clifford
algebra. In particular, the transfer
matrix can be viewed as a dilation generated by a conformal bivector, while its eigenvectors correspond to null combinations of Clifford generators, closely paralleling the emergence of Majorana fermionic degrees of freedom. In the two-dimensional case, the standard
eigenvalue equation for the row-to-row transfer
matrix is reinterpreted as a dispersion relation for quasiparticle excitations, exposing the connection between the Ising model and a theory of free Majorana
fermions. While all the explicit exact results recovered are well known, this
geometric reformulation provides a unified algebraic framework which is compact and physically interpretable. Specifically, this clarifies the role of scale transformations, fermionic modes, and duality in the Ising model. We believe this approach offers a useful pedagogical complement to more conventional fermionic, Grassmann, or field theoretic treatments.
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All authors N. Johnson, D. Marenduzzo, A. Morozov, E. Orlandini, G. M. Vasil
Strongly Correlated Electrons
Field-induced jammed polyhex spin liquid in the honeycomb Ising antiferromagnet
Nicholas Franklin, Jacob Richards and Harry Lane
We analyze the ground state properties of the honeycomb Ising antiferromagnet in an external
magnetic field. We demonstrate the existence of extensive ground state degeneracy at finite field that maps to a polyhex tiling problem. This state is shown to be a jammed
spin liquid, with no local zero modes connecting ground states. Through Monte Carlo simulations, we explore the properties of these states and show that the
spin diffusion can be controlled by the
magnetic field strength. By considering
quantum fluctuations, we demonstrate that transverse coupling partially lifts the ground state degeneracy, selecting an extensive subspace of non-periodic tilings of 12-hexes. We suggest that the jammed polyhex
spin liquid phase exists in an experimentally realizable region of parameter space and may be present in the FePX$_3$ compounds.
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Materials Science
Improved Electrochemical Performance and Diffusion kinetics by Boron-doping in Na$_{0.66}$Mn$_{0.8}$Fe$_{0.2}$O$_{2}$ Layered Cathodes for Sodium-Ion Batteries
Jayashree Pati, P. Senthilkumar, Deepak Seth et al. (+6 more)
We report the electrochemical investigation and study the
diffusion kinetics of boron doped Na$_{0.66}$Mn$_{0.8}$Fe$_{0.2}$O$_{2}$ (B-NMFO) cathode materials for sodium-ion batteries. Notably, the B-NMFO cathode exhibits improved specific capacity of 163 mAh g$^{-1}$ as compared to 133 mAhg$^{-1}$ at 0.1~C for the NMFO cathode. Further, we observe better capacity retention of 70% for B-NMFO as compared to the NMFO (60%) at 1 C after 200 cycles, indicating high structural stability due to the presence of strong B-O bonds. The
diffusion coefficient evaluation through galvanostatic intermittent titration technique and cyclic voltammetry, which is found to be in the range of 10$^{-8}$–10$^{-10}$ cm$^{2}$s$^{-1}$. Interestingly, the temperature dependent distribution of relaxation time (DRT) analysis provides a clear understanding about the individual physical processes occurring at different time domains during the electro-chemical testing. Moreover, density functional theory is employed to determine the energetics and the electronic properties of B-NMFO, which suggests that the interstitial tetrahedral sites, especially those next to vacancies, are the dominant incorporation path ways for B in the host structure. Additionally, classical molecular dynamics (MD) simulations are applied to gain insights into the Na-ion transport properties in the bulk structures cathode materials.
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All authors Jayashree Pati, P. Senthilkumar, Deepak Seth, Riya Gulati, Manish Kr. Singh, Madhav Sharma, Anita Dhaka, M. Ali Haider, Rajendra S. Dhaka
Statistical Mechanics
Conformal Invariance of the large-$N$ limit of the $O(N)$ universality class
Santiago Cabrera, Gonzalo De Polsi, Adam Rançon et al. (+1 more)
Conformal
symmetry is expected to be realized in many
equilibrium statistical mechanical systems at criticality. Although this is certainly true in two-dimensional systems, the three-dimensional case is subtler, and only a few proofs exist, only so in very specific cases. In this work, we give two proofs for the large $N$ limit of the $O(N)$ universality class within the non-perturbative renormalization group framework: one functional, and one vertex-by-vertex in
Fourier space. While doing so, we unveil how the theory is structured in order for conformal
symmetry to be realized. As a consequence, we shed light on what to expect, on rather general grounds, for a theory to be conformally invariant.
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All authors Santiago Cabrera, Gonzalo De Polsi, Adam Rançon, Nicolás Wschebor
Materials Science
Bottom-up realization of a type-II organic-TMD heterointerface: Pentacene on monolayer WS2
Michele Capra, Christian S. Kern, Mira S. Arndt et al. (+11 more)
Stacked van der Waals
heterostructures based on transition metal dichalcogenides (TMDs) exhibit a rich variety of exotic interfacial phenomena. Substituting one component with an organic
semiconductor (OSC) enables the design of hybrid
heterostructures with tunable functionalities for optoelectronic, photovoltaic, and spintronic applications. In this work, exploiting scanning tunneling spectroscopy (STS), photoemission orbital
tomography (POT) and G0W0 electronic structure calculations, we experimentally and theoretically demonstrate the self-assembly of an ordered single layer of pentacene (5A) above monolayer WS2, exhibiting a type-II (staggered) band
alignment in the hybrid 5A/WS2 interface. Central to this result is the synthesis of extended, atomically flat WS2 - an essential prerequisite for a highly ordered and electronically homogeneous OSC/TMD interface - which can only be reliably achieved via bottom-up growth, most notably molecular beam epitaxy (MBE). We realize this by leveraging Au(111) as an atomically clean and conductive sample for epitaxial growth - a necessary requirement for reliable and comparable STS/POT characterizations. The high quality of the synthesized
heterostructure, together with its type-II band
alignment, establishes pentacene/WS2 as a model system for orbital-resolved studies of charge transfer, energy-level renormalization, and non-
equilibrium interfacial processes in hybrid organic-inorganic-2D
heterostructures.
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All authors Michele Capra, Christian S. Kern, Mira S. Arndt, Karl J. Schiller, Max Niederreiter, Francesco Presel, Iolanda Di Bernardo, Marco Gruenewald, Torsten Fritz, Stefan Tappertzhofen, Martin Sterrer, Peter Puschnig, Mirko Cinchetti, Giovanni Zamborlini
Materials Science
A step-by-step workflow to extract the genuine circular dichroism of thin films
Franziska Schölzel, Arina Narudin, Aleksandra Ciesielska et al. (+5 more)
Circular Dichroism (CD) spectroscopy has evolved from a purely solution based method towards a powerful tool in the analysis of
chiral thin films. Although a straightforward technique, the genuine CD signal is often accompanied by artifacts arising from optical anisotropy and instrumental imperfections. This tutorial presents a two-step workflow that reliably isolates the orientation invariant CD response for anisotropic thin films by combining azimuthal sample rotation with sample flipping. For this purpose, a home-built sample stage was developed, which enables systematic suppression of many anisotropy-induced artifacts in commercial CD spectrophotometers. Both a detailed description of the setup itself as well as the needed python script are provided. The reliability of the workflow is demonstrated on two selected samples from different research fields:
chiral molecules attached to metallic surfaces as well as metal halide perovskites incorporating
chiral spacer molecules
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All authors Franziska Schölzel, Arina Narudin, Aleksandra Ciesielska, Alexander Ehm, Dietrich R.T. Zahn, Wouter van Gompel, Simon Kahmann, Georgeta Salvan
Mesoscale and Nanoscale Physics
Electrical tunability of terahertz nonlinearity in graphene
Sergey Kovalev, Hassan A. Hafez, Klaas-Jan Tielrooij et al. (+15 more)
Graphene is conceivably the most nonlinear optoelectronic material. Its nonlinear optical coefficients in the terahertz (THz) frequency range surpass those of other materials by many orders of magnitude. This, in particular, allows one to use
graphene for extremely efficient up-conversion of sub-THz electronic input signals into the THz frequency range at room temperature and under ambient conditions, thus paving the way for practical
graphene-based ultrahigh-frequency electronic technology. Here, we show that the THz nonlinearity of
graphene can be efficiently controlled using electrical gating, with gating voltages as low as a few volts. For example, optimal electrical gating enhances the power conversion efficiency in THz third-harmonic generation in
graphene by about two orders of magnitude. This essentially converts
graphene from an almost perfectly linear, inert electronic material to a material with the highest possible THz nonlinearity. We demonstrate gating control of THz nonlinearity of
graphene for both ultrashort single-cycle and quasi-monochromatic multi-cycle input signals. Our experimental results are in quantitative agreement with a physical model of
graphene nonlinearity, describing the time-dependent thermodynamic balance maintained within the electronic population of
graphene during interaction with ultrafast electric fields. Our results can serve as a basis for straightforward and accurate design of devices and applications for efficient electronic signal processing in
graphene at ultra-high frequencies.
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All authors Sergey Kovalev, Hassan A. Hafez, Klaas-Jan Tielrooij, Jan-Christoph Deinert, Igor Ilyakov, Nilesh Awari, David Alcaraz, Karuppasamy Soundarapandian, David Saleta, Semyon Germanskiy, Min Chen, Mohammed Bawatna, Bertram Green, Frank H. L. Koppens, Martin Mittendorff, Mischa Bonn, Michael Gensch, Dmitry Turchinovich
Materials Science
Physical Basis for Band Transport and Dimensionality in Amorphous Oxide Semiconductor Field-Effect Transistors
Ananth Dodabalapur, Chankeun Yoon and Xiao Wang
A consistent and widely accepted physical basis for interpretation of charge transport in amorphous
oxide semiconductor (AOS) field-effect transistors (FETs), and more generally device physics, has been hampered by uncertainties in crystalline order, dimensionality, and the effects of a significant density of traps. The overarching theme of this paper is to build and justify a much-needed conceptual framework for describing advanced AOS transistors, particularly those with very small channel lengths. Combining new work and selecting prior research results on charge transport and device physics together with literature reports from various groups on morphology, physical properties, electronic structure and percolation effects, the main evidence that is available in support of a trap-influenced band transport picture in quasi-2-dimensional channels in high mobility AOS FETs is presented.
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Statistical Mechanics
Dynamical Fluctuation-Response Relations
Timur Aslyamov and Massimiliano Esposito
We derive exact dynamical fluctuation-response relations (FRRs) for time-integrated observables of any nonautonomous Markov jump process. The finite-time covariance splits into an initial variability and an integral of response kernels along the driven dynamics. The identity sharpens the dynamical response thermodynamic and kinetic uncertainty relations and fluctuation-response inequalities (FRIs). For autonomous processes, dynamical FRRs yield two complementary frequency-domain relations. Steady-state FRRs are recovered in the long time limit, along with the fluctuation-dissipation
theorem and Onsager reciprocity for detailed-balance dynamics. The importance of initial variability for slowly relaxing systems is also highlighted.
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Materials Science · Cross-listed from physics.chem-ph
Errors that matter: Uncertainty-aware universal machine-learning potentials calibrated on experiments
Matthias Kellner, Teitur Hansen, Thomas Bligaard et al. (+2 more)
Machine-learning models of atomic-scale interactions achieve the accuracy of the
quantum mechanical calculations on which they are trained, but at a dramatically lower computational cost. Their predictions can be made trustworthy by uncertainty quantification techniques that estimate the residual error relative to their reference. These errors, however, do not include uncertainty contributions from the approximations inherent in the electronic structure calculations, which are often the main source of discrepancy with empirical observations. We construct an ensemble of ML potentials trained on multiple electronic-structure references and calibrate it against experimental data on cohesive energies, atomization energies,
lattice constants and bulk
moduli of simple materials and molecules, similar to the uncertainty-aware functional distribution approach. The resulting ensemble of models, which we call PET-UAFD, can be used to simulate matter across a wide range of compositions and thermodynamic conditions. By comparison with experimental measurements of the density and structure of
liquids, we demonstrate that, even outside the static properties on which it was calibrated, PET-UAFD enables predictions that are as accurate against experiments as the best available electronic-structure reference and that the spread in the ensemble can be used to assess the reliability of such predictions. We also introduce the PET-EXP protocol that uses shallow ensembles and statistical reweighting techniques to provide accurate estimates of uncertainty relative to experimental measurements at virtually no additional cost over a simulation based on a single conventional ML potential. Ultimately, this approach provides a practical and inexpensive approach to elevate machine-learning potentials from faithful interpolators of approximate theories to genuinely predictive tools anchored in experimental reality.
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All authors Matthias Kellner, Teitur Hansen, Thomas Bligaard, Karsten Wedel Jacobsen, Michele Ceriotti
Materials Science
Step- and terrace-resolved crystal truncation rod scattering from vicinal surfaces under coherent heteroepitaxy
Junlin Wu, Erqi Xu, Qihui Lin et al. (+4 more)
We develop a general theory of
crystal truncation rod (CTR) scattering from vicinal surfaces with a coherently strained heteroepitaxial film. The formalism incorporates film-induced interference fringes, full elastic
lattice distortion, terrace ordering, surface reconstruction, and real-time growth
evolution within a unified description. Comparison between Nagai model and elasticity-based model shows that the
lattice tilt is nearly identical in the two approaches, whereas the elasticitybased model predicts an additional triclinic deformation arising from shear strain. This deformation has little effect on specular CTRs but strongly modifies non-specular rods, making them a sensitive probe of the full elastic state of coherent epitaxial films. We further show that the characteristic sensitivity of vicinal CTRs to terrace ordering, surface reconstruction, and terrace-resolved compositional modification remains robust in the presence of a coherent film. Representative calculations for InGaN/GaN demonstrate that the framework enables quantitative interpretation of both static and real-time CTR measurements and provides access to step- and terrace-resolved structural and kinetic information during heteroepitaxial growth.
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All authors Junlin Wu, Erqi Xu, Qihui Lin, Jiaqing Yue, Jiale Wang, Zihao Xu, Guangxu Ju
Statistical Mechanics
Generalized flux-weighted boundary walls in kinetic models
Luca Barbieri and Pierfrancesco Di Cintio
We present a technique to investigate the stationary states of a system of a collisionless system confined by an external potential and coupled to boundary reservoirs through prescribed reinjection rules. We consider a family of boundary conditions parametrized by an integer $n$, corresponding to different velocity distributions imposed at the boundaries, generalizing the standard flux-weighted Maxwellian scheme. By combining Liouville's
theorem with the boundary injection rule, we derive an explicit analytical expression for the stationary distribution function. This framework provides a direct link between microscopic boundary dynamics and macroscopic stationary profiles. We show that thermal
equilibrium is recovered only for the standard flux-weighted injection method, while for all other cases the system relaxes to manifestly non-thermal stationary states. The resulting density and temperature profiles exhibit non-trivial spatial structures, including non-monotonic behaviour and temperature gradients induced by the boundary conditions alone. Analytical predictions for stationary moments are obtained in closed form for representative cases and are nicely reproduced by particle-based numerical simulations.
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Materials Science
Electronic and optical properties of arsenic monolayers: from planar honeycomb to the puckered phase
Niloufar Dadkhah and Walter R. L. Lambrecht
Group-V monolayer materials exhibit intriguing electronic and optical properties, influenced by their unique
crystal symmetries and structural phases. In this work, we study arsenic monolayers, investigating their electronic and optical properties across different phases, including planar, and puckered forms, using density functional theory (DFT) and quasi-particle self-consistent $GW$ (QS$GW$) methods, with and without vertex contributions (ladder diagrams) and examine the effects of
spin-orbit coupling and the orbital composition of the bands. The Bethe-Salpeter equation (BSE) method is used to study the optical response and the band origin of the low lying
excitons is determined. The gradual transformation from the puckered $\alpha$-phase to the flat honeycomb structure is studied under biaxial strain and the
evolution of the band structure and optical response is described in terms of band inversions of bands of different orbital character.
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