Materials Science
Defect thermodynamics of orthorhombic Ba$_2$In$_2$O$_5$: First-principles calculations on the role of oxygen dumbbell interstitials
Rachele Sciotto and Karsten Albe
The brownmillerite-type barium indate (Ba$_2$In$_2$O$_5$) is a potential electrolyte for mixed ionic-electronic conduction in solid
oxide fuel
cells. Revealing the defect chemistry of this material is key to understanding its ionic and electronic conductivity. In this contribution, we report the existence of oxygen interstitials in a dumbbell configuration, which are also observed in In$_2$O$_3$. Using Density Functional Theory within the generalized gradient approximation, complemented by selected hybrid-functional calculations, we investigate vacancies, various oxygen interstitials, and Frenkel pairs. In doing so, we evaluate the formation energies, charge transition levels, and concentrations as a function of oxygen partial pressure. Our results show that oxygen vacancies and interstitials dominate the intrinsic defect landscape. Among the interstitials, we identify stable dumbbell configurations that remain neutral across the entire band gap. Other interstitial configurations exhibit charged states and become the prevailing compensating defects at high oxygen partial pressures, alongside oxygen vacancies. Our results provide a consistent picture of the thermodynamics of intrinsic defects in barium indate, setting the stage for future investigations of the
diffusion dynamics of oxygen vacancies and interstitials.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from physics.bio-ph
Inheritance Entropy: A Model-Independent Method to Probe the Hereditary Structure of Cell Lineage Trees
Alessandro Allegrezza, Riccardo Beschi, Domenico Caudo et al. (+14 more)
Human bone marrow stromal
cells (BMSC) include skeletal stem
cells with ground-breaking therapeutic potential. However, BMSC colonies have very heterogeneous in vivo behaviour, due to their different potency; this unpredictability is the greatest hurdle to the development of skeletal regeneration therapies. Colony-level heterogeneity urges a fundamental question: how is it possible that one colony as a collective unit behaves differently from another one? If
cell-to-
cell variability were just an uncorrelated random process, a million
cells in a transplant-bound colony would be enough to yield statistical homogeneity, hence washing out any colony-level traits. A possible answer is that the differences between two originating
cells are transmitted to their progenies and collectively persist through an hereditary mechanism. But non-genetic inheritance remains an elusive notion, both at the experimental and at the theoretical level. Here, we prove that heterogeneity in the lineage
topology of BMSC clonal colonies is determined by heritable traits that regulate
cell-cycle exit. The cornerstone of this result is the definition of a novel
entropy of the colony, which measures the hereditary ramifications in the distribution of inactive
cells across different branches of the proliferation tree. We measure the
entropy in 32 clonal colonies, obtained from single-
cell lineage tracing experiments, and show that in the greatest majority of clones this
entropy is decisively smaller than that of the corresponding non-hereditary lineage. This result indicates that hereditary epigenetic factors play a major role in determining cycle exit of bone marrow stromal
cells.
Read the full abstract ▾
All authors Alessandro Allegrezza, Riccardo Beschi, Domenico Caudo, Andrea Cavagna, Alessandro Corsi, Antonio Culla, Samantha Donsante, Giuseppe Giannicola, Irene Giardina, Giorgio Gosti, Tomas S. Grigera, Stefania Melillo, Biagio Palmisano, Leonardo Parisi, Lorena Postiglione, Mara Riminucci, Francesco Saverio Rotondi
Materials Science
Multiferroic-like Quasiparticles in Ferroelectrics
Ping Tang and Gerrit E. W. Bauer
Multiferroics are materials with coexisting electric and
magnetic orders that are of central importance for fundamental research and technological applications. Unfortunately, intrinsic multiferroics that operate at room temperature remain rare due to an apparent incompatibility between magnetism and ferroelectricity. Here we predict that a pure ferroelectric support multiferroic-like quasiparticles, termed “multiferrons", that simultaneously carry static
magnetic and electric dipoles. The electric dipole moment emerges from the parity-odd anharmonicity of the ferroelectric dynamics, while the
magnetic moment has both paramagnetic and diamagnetic origins generated by circularly polarized transverse fluctuations of the ferroelectric polarization. In contrast to the established “dynamical multiferroicity" of circularly polarized
phonons, which involve only oscillating electric dipoles, multiferrons cause, apart from Zeeman and Einstein-de Haas effects, a linear dc Stark response,
giant electric-field-tunable second-harmonic generation in the THz-frequency regime, and a finite magnetoelectric cross coupling. Multiferrons open a new route toward nonlinear THz optical applications and offer multiferroic functionalities with simple ferroelectrics.
Read the full abstract ▾
Materials Science
Stability Criteria and Optoelectronic Properties of Mg3ZBr3 (Z = As, Sb, Bi) Perovskites for Evaluating the Performance in PIN Photo Diode
Md Mohiuddin, Mohammed Mehedi Hasan and Alamgir Kabir
The toxicity and stability issues of lead-based perovskites motivate the search for non-toxic, durable alternatives. This work examines lead-free $\mathrm{Mg_3ZBr_3}$ ($Z=\mathrm{As,Sb,Bi}$) halide perovskites as optoelectronic materials, with emphasis on $\mathrm{Mg_3AsBr_3}$ and $\mathrm{Mg_3SbBr_3}$. First-principles calculations establish cubic $Pm\bar{3}m$ frameworks stabilized by strong Mg–Br linkages, and indirect band gaps of $2.0645\,\mathrm{eV}$ for $\mathrm{Mg_3AsBr_3}$ and $1.6533\,\mathrm{eV}$ for $\mathrm{Mg_3SbBr_3}$ obtained using hybrid functionals. Optical spectra show a rapid rise in absorption above the gap and an increasing static dielectric response along $\mathrm{As}\rightarrow\mathrm{Sb}\rightarrow\mathrm{Bi}$, indicating strengthened light–matter coupling.
Phonon dispersions lack imaginary branches, confirming dynamical stability, and exhibit large mode anharmonicity (Grüneisen signatures) consistent with soft-
lattice heat transport. Moving down the pnictogen series expands the
lattice and lowers the Goldschmidt tolerance factor, while enhanced pnictogen–Br $p$-orbital hybridization and stereochemically active $n\mathrm{s}^{2}$ lone pairs (Sb, Bi) narrow the band gap and increase the optical dielectric response. Elastic analyses confirm Born stability and moderate stiffness, with Hill-averaged bulk
moduli decreasing from approximately $44\,\mathrm{GPa}$ ($\mathrm{Mg_3AsBr_3}$) to $35\,\mathrm{GPa}$ ($\mathrm{Mg_3BiBr_3}$). Drift–
diffusion $p$–$i$–$n$ simulations qualitatively track band-edge-limited spectra, aligning with the computed gaps. Together, these results position these materials as promising lead-free candidates for stable thin-film photodiode and photovoltaic applications.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from hep-th
Covariant field theory of 3D massive fractons
Erica Bertolini, Matteo Carrega, Nicola Maggiore et al. (+1 more)
We construct a covariant and gauge-invariant theory describing massive fractons in three spacetime dimensions, based on a symmetric rank-2 tensor field. The model includes a Chern-Simons-like term that plays a dual role: it generates a topological mass for the tensor gauge field and simultaneously acts as a source of intrinsic fractonic matter. This dual mechanism is novel and leads to a propagating fractonic degree of freedom described by a massive Klein-Gordon equation. The theory propagates two degrees of freedom – one massive, one massless – whose number is preserved in the massless limit, in analogy with the Maxwell-Chern-Simons mechanism of Deser-Jackiw-Templeton. We analyze the resulting equations of motion and show that the intrinsic fractonic matter satisfies Gauss- and Ampère-like laws, with conserved dipole and trace of the quadrupole moment. Upon coupling to external matter, a second fractonic sector emerges, leading to a coexistence of intrinsic and extrinsic subsystems with different mobility and conservation properties. Our model provides a unified framework for describing massive fractons with internal structure, and offers a covariant setting for exploring their interactions and extensions.
Read the full abstract ▾
All authors Erica Bertolini, Matteo Carrega, Nicola Maggiore, Daniel Sacco Shaikh
Disordered Systems and Neural Networks
Large deviations in the many-body localization transition: The case of the random-field XXZ chain
Greivin Alfaro Miranda, Fabien Alet, Giulio Biroli et al. (+3 more)
The effect of rare system-wide resonances in the many-body localization (MBL) transition has recently attracted significant
attention. They are expected to play a prominent role in the stability of the MBL phase, prompting the development of new theoretical frameworks to properly account for their statistical weight. We employ a method based on an analogy with mean-field disordered glassy systems to characterize the statistics of transmission amplitudes between distant many-body configurations in
Hilbert space, and apply it to the random-field XXZ
spin chain. By introducing a Lagrange multiplier, which formally plays the role of an effective temperature controlling the influence of extreme outliers in the heavy-tailed distribution of propagators, we identify three distinct regimes: (i) an ergodic phase with uniform spreading in
Hilbert space, (ii) an intermediate regime where delocalization is driven by rare, disorder-dependent long-range resonances, and (iii) a robust MBL phase where such resonances cannot destabilize localization. We derive a finite-size phase diagram in the disorder–interaction plane both in the
spin and in the Anderson basis that quantitatively agrees with recent numerical results based on real-space
spin-
spin correlation functions. We further demonstrate that even infinitesimal interactions can destroy the Anderson
insulator at finite disorder, with the critical disorder remaining finite down to small interaction strengths. By visualizing resonant transmission pathways on the
Hilbert space graph, we provide a complementary perspective to real-space and spectral probes, revealing how the destabilization of the MBL phase at finite sizes stems from the emergence of resonant paths that become progressively rarer and shorter-ranged deep in the localized phase.
Read the full abstract ▾
All authors Greivin Alfaro Miranda, Fabien Alet, Giulio Biroli, Leticia F. Cugliandolo, Nicolas Laflorencie, Marco Tarzia
Materials Science
Imaging atoms in real-space with elemental selectivity
Harry Mönig
Tip functionalization in AFM allows imaging organic nano-structures with sub-molecular resolution. Here, recent progress by using atomically defined copper-
oxide tips is discussed. With their outstanding
rigidity and elemental selectivity on metal-
oxide surfaces, these probes constitute a powerful approach for the atomic-scale characterization of metal-
oxide surfaces and a major step towards standardized scanning probe microscopy.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Fibonacci-Engineered Spin and Charge Thermoelectrics in a Long Range Su-Schrieffer-Heeger Chain: A Pathway to Giant Figure of Merit
Ranjini Bhattacharya and Souvik Roy
In this work, we present a novel investigation into the
spin-dependent thermoelectric performance of an extended Su-Schrieffer-Heeger (SSH) model, showcasing for the first time how its intrinsic
spin filtration mechanism can be strategically harnessed to function as an efficient
spin thermoelectric generator. By introducing a Fibonacci-type aperiodic modulation in the onsite energies, we engineer a deterministic disorder that mimics realistic aperiodic systems and profoundly influences transport characteristics. Furthermore, we incorporate both nearest-neighbor (NN) and next-nearest-neighbor (NNN) hopping amplitudes with tunable cosine dependencies, enabling us to meticulously explore the intricate interplay between these hopping processes and its implications on thermoelectric behavior. Our analysis reveals a remarkable enhancement in the dimensionless thermoelectric figure of merit ZT for both charge and
spin transport channels, under carefully optimized conditions. Notably, the
spin thermoelectric response exhibits distinct advantages, opening a new frontier in the design of next-generation thermoelectric materials and devices. This qualitative study not only deepens our understanding of aperiodic topological systems but also establish a foundational framework for exploiting
spin-based thermoelectricity in low-dimensional platforms.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from quant-ph
Quantum Reversibility Meets Classical Reverse Diffusion
Ryota Nasu, Gota Tanaka and Asato Tsuchiya
Bayes' rule connects forward and reverse processes in classical probability theory, and its
quantum analogue has been discussed in terms of the Petz (transpose) map. For
quantum dynamics governed by the Lindblad equation, the corresponding Petz map can also be written in Lindblad form. In classical
stochastic systems, the analogue of the Lindblad equation is the Fokker-Planck equation, and applying Bayes' rule to it yields the reverse
diffusion equation underlying modern
diffusion-based generative models. It is known that a semiclassical approximation of the Lindblad equation yields the Fokker-Planck equation for the Wigner function, which is a quasiprobability distribution defined on phase space as the Wigner transform of the density operator. Here we demonstrate that applying the same approximation to the Lindblad equation associated with the Petz map produces an equation that coincides with that obtained from the Fokker-Planck equation via Bayes' rule. This finding establishes a direct correspondence between the Petz map and Bayes' rule, unifying
quantum reversibility with classical reverse
diffusion.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Semiconductor-Semimetal Transition in van der Waals Carbyne Crystals
Daniele Barettin, Stella V. Kavokina, Evgeny L. Ivchenko et al. (+1 more)
Freestanding van der Waals
crystals made of single-atom carbon chains (carbynes) have been recently realized technologically. Here we investigate their electronic and optical properties experimentally, by continuous-wave and time-resolved photoluminescence spectroscopy, and theoretically. Employing a fully three-dimensional tight-binding formalism benchmarked against density functional theory calculations we predict the semimetal-
semiconductor transition to occur in van der Waals carbyne
crystals composed by the chains of about 42 atoms long. The
semiconductor phase is characterized by a
hyperbolic van Hove singularity which gives rise to unconventional
hyperbolic exciton states. Experimentally, we access the
semiconductor phase, where resonant features associated with
hyperbolic excitons are clearly visible. The
exciton oscillator strength is found to be strongly sensitive to the length of carbon chains: our experiments show that it decreases with the increasing chain length. This tendency, confirmed by the theoretical modeling, manifests the
evolution of the
hyperbolic exciton state on the way to the
semiconductor-semimetal crossover. Our approach accounts for the actual crystalline geometry, including alternating intra-chain hoppings and inter-chain couplings. By fitting tight-binding dispersions to density functional theory data we extract consistent parameters and establish a comprehensive framework for the physics of carbyne
crystals. This study paves the way towards efficient band-gap engineering in ultimate one-dimensional carbon
crystals.
Read the full abstract ▾
All authors Daniele Barettin, Stella V. Kavokina, Evgeny L. Ivchenko, Alexey V. Kavokin
Materials Science
Interpretable machine learning of magnetic transition temperature in Heusler magnets via hierarchical dependence extraction
Jean-Baptiste Morée, Ryotaro Arita and Juba Bouaziz
We employ interpretable machine learning to analyze the material dependence of the
magnetic transition temperature $T_c$ in
ferromagnetic and ferrimagnetic Heusler compounds. For over 200 candidate materials with the same $F\overline{4}3m$
crystal structure but different chemical formulae and
lattice constants, we consider both experimental $T_c$ and those computed via classical Monte Carlo simulations using
magnetic interactions derived from ab initio calculations. We use the hierarchical dependence extraction (HDE) procedure [Morée and Arita, Phys. Rev. B 110, 014502 (2024)] to determine how $T_c$ depends on chemical composition and
magnetic moments, from leading to higher-order effects, and use these dependencies to construct an explicit expression for $T_c$. Our results show that the HDE framework predicts $T_c$ with accuracy comparable to other machine-learning approaches such as neural network and random forest
algorithms while remaining fully interpretable. $T_c$ is primarily governed by the proportions of Fe, Co, and Mn, increasing systematically with their concentration. These findings clarify how chemical composition and
magnetic moments influence $T_c$ in collinear Heusler
alloys and support the use of the HDE for computationally guided discovery of new functional materials with tailored $T_c$ values.
Read the full abstract ▾
Materials Science
Persistence of Layer-Tolerant Defect Levels in ReS2
Nikhilesh Maity, Shibu Meher, Manoj Dey et al. (+1 more)
Defects in two-dimensional (2D)
semiconductors play a decisive role in determining their electronic, optical, catalytic and
quantum properties. Understanding how defect energy levels respond to variations in layer thickness is essential for achieving reproducible and scalable device performance. We report the persistence of layer-tolerant defect levels in rhenium disulfide (ReS2), where both donor- and acceptor-type charge transition levels remain nearly unchanged from monolayer to bulk in both AA and AB stacking. The associated two-level
quantum system also retains its character across thicknesses, enabling ReS2 to serve as a platform for layer-tolerant single-
photon emitters. The invariance arises from the interplay between electronic energy minimization and structural relaxation, which together counteract
quantum confinement and reduced dielectric screening. Additionally, the intrinsically weak interlayer coupling in ReS2 plays a crucial role. Our findings uncover the microscopic origin of this unique behavior, distinguishing ReS2 from other transitionmetal dichalcogenides and highlighting its potential for thickness-independent optoelectronic and
quantum photonic applications.
Read the full abstract ▾
All authors Nikhilesh Maity, Shibu Meher, Manoj Dey, Abhishek Kumar Singh
Materials Science
Robust Material Properties in Epitaxial In$_2$Te$_3$ Thin Films Across Varying Thicknesses
Maximilian Buchta, Felix Hoff, Lucas Bothe et al. (+8 more)
Sesqui-chalcogenides serve as a critical bridge between traditional
semiconductors and
quantum materials, offering significant potential in applications such as thermoelectrics, phase change
memory, and topological
insulators. While considerable
attention has been focused on antimony- and bismuth-based compounds, characterized by substantial property changes upon reduction in film thickness, indium containing sesqui-chalcogenides like In$_2$Te$_3$ are emerging as promising candidates for photovoltaics and electronic devices. However, the effects of film thickness on the properties of In$_2$Te$_3$ remain largely unexplored. In this study, we investigate high-quality In$_2$Te$_3$ thin films grown by molecular beam epitaxy on Si(111) substrates across a thickness range from 2.7 nm to 24 nm. We employ X-ray diffraction, reflective high-energy electron diffraction and atomic force microscopy to analyze both the
crystal structure and film morphology. Additionally, we utilize broadband optical spectroscopy alongside femtosecond pump-probe measurements and Raman spectroscopy to assess optical and vibrational properties, respectively. Our analysis reveals that material properties exhibit minimal dependence on film thickness, contrasting sharply with behavior observed in other chalcogenides such as Sb$_2$Te$_3$, Bi$_2$Se$_3$, or GeTe. This phenomenon can be attributed to covalent bonding present in In$_2$Te$_3$, which differs from those in its antimony- and bismuth-containing counterparts.
Read the full abstract ▾
All authors Maximilian Buchta, Felix Hoff, Lucas Bothe, Niklas Penner, Christoph Ringkamp, Thomas Schmidt, Timo Veslin, Ka Lei Mak, Jonathan Frank, Dasol Kim, Matthias Wuttig
Statistical Mechanics
Fingerprints of cluster-based Haldane and bound-magnon states in a spin-1 Heisenberg diamond chain
Azam Zoshki, Hamid Arian Zad, Katarina Karlova et al. (+1 more)
We investigate
magnetic and thermodynamic properties of a
spin-1 Heisenberg diamond chain in a
magnetic field using a combination of analytical and numerical methods including the variational approach, exact diagonalization, density-
matrix renormalization group, localized-
magnon theory, and
quantum Monte Carlo simulations. In the unfrustrated regime, the model exhibits a
quantum ferrimagnetic phase that captures key
magnetic features of the nickel-based polymeric compound [Ni3(OH)2(C4H2O4)(H2O)4].2H2O such as a at minimum in the temperature dependence of the susceptibility times temperature product and an intermediate one-third magnetization plateau. In the frustrated regime, we uncover a rich variety of unconventional
quantum phases including uniform and cluster-based Haldane states, fragmented monomer-dimer phase, and bound-
magnon crystals. Analysis of the adiabatic temperature change and
magnetic Gruneisen parameter reveals an enhanced magnetocaloric effect near field-induced transitions between these exotic
quantum phases. Additionally, we demonstrate that the frustrated
spin-1 diamond chain can operate as an efficient working medium of a
quantum Stirling engine, which approaches near-optimal efficiency when driven into these unconventional
quantum states.
Read the full abstract ▾
All authors Azam Zoshki, Hamid Arian Zad, Katarina Karlova, Jozef Strecka
Soft Condensed Matter · Cross-listed from physics.flu-dyn
Multiscale transitional flow in anisotropic nanoparticle suspensions revealed by time-resolved x-ray scatter microscopy
Kesavan Sekar, Viney Ghai, Reza Ghanbari et al. (+6 more)
Complex fluids transition from laminar to transitory flow above a critical control parameter, akin to their Newtonian counterparts. In a continuum mechanics sense, fluid elements follow the ensuing complex trajectories, giving rise to secondary flows in terms of macroscopic
vortices and patterns thereof. However, if we replace idealized fluid elements with actual anisotropic nanoparticles, would their trajectories still reveal the same spatiotemporal behavior as the macroscopic flow field? This question is fundamental for complex fluids, where fully developed
turbulence is suppressed by high viscosities and where understanding particle-flow coupling is central to transport, processing, and structure formation. To address this question, we develop small-angle x-ray scatter microscopy of unprecedented temporal resolution combined with polarized light imaging, thereby bridging seven orders of magnitude in lengtscales. Proof-of-principle is demonstrated on a classical stability problem, Taylor-Couette flow, of platelet-like
graphene oxide nanoparticle and rod-like cellulose nanocrystal suspensions. The analysis shows hitherto hidden, markedly different multiscale dynamics underlying flow stability; while the platelet-like particles follow the wavy motion of the macroscopic, secondary flow field, the rod-like particles exhibit high-frequency motion that is uncorrelated with the
vortex instabilities.
Read the full abstract ▾
All authors Kesavan Sekar, Viney Ghai, Reza Ghanbari, Marko Bek, Marianne Liebi, Aleksandar Matic, Ann E. Terry, Kim Nygård, Roland Kádár
Soft Condensed Matter
Granular fluid in an arbitrary external potential: spontaneous convection, self-phoresis
Alvaro Domínguez and Nagi Khalil
The hydrodynamic stationary states of a granular fluid are addressed theoretically when subject to energy injection and a time-independent, but otherwise arbitrary external potential force. When the latter is not too symmetrical in a well defined sense, we show that a quiescent stationary state does not exist, rather than simply being unstable and, correspondingly, a steady convective state emerges spontaneously. We also unveil an unexpected connection of this feature with the self-diffusiophoresis of catalytically active particles: if an intruder in the granular fluid is the source of the potential, it will self-propel according to a recently proposed mechanism that lies beyond linear response theory, and that highlights the role of the intrinsic nonequilibrium nature of the state of the granular bath. In both scenarios, a state-dependent characteristic length of the granular fluid is identified which sets the scale at which the induced flow is the largest.
Read the full abstract ▾
Disordered Systems and Neural Networks
Overparametrization bends the landscape: BBP transitions at initialization in simple Neural Networks
Brandon Livio Annesi, Dario Bocchi and Chiara Cammarota
High-dimensional non-convex loss landscapes play a central role in the theory of Machine Learning. Gaining insight into how these landscapes interact with gradient-based optimization methods, even in relatively simple models, can shed light on this enigmatic feature of neural networks. In this work, we will focus on a prototypical simple learning problem, which generalizes the Phase
Retrieval inference problem by allowing the exploration of overparametrized settings. Using techniques from field theory, we analyze the spectrum of the Hessian at initialization and identify a Baik-Ben Arous-Péché (BBP) transition in the amount of data that separates regimes where the initialization is informative or uninformative about a planted signal of a teacher-student setup. Crucially, we demonstrate how overparameterization can bend the loss landscape, shifting the transition point, even reaching the information-theoretic weak-recovery threshold in the large overparameterization limit, while also altering its qualitative nature. We distinguish between continuous and discontinuous BBP transitions and support our analytical predictions with simulations, examining how they compare to the finite-N behavior. In the case of discontinuous BBP transitions strong finite-N corrections allow the
retrieval of information at a signal-to-noise ratio (SNR) smaller than the predicted BBP transition. In these cases we provide estimates for a new lower SNR threshold that marks the point at which initialization becomes entirely uninformative.
Read the full abstract ▾
Materials Science
Ideal Nodal-Sphere Semimetal in the Three-Dimensional Boron Allotrope CT-B$_{24}$
Xiao-jing Gao, Yanfeng Ge and Yan Gao
Nodal-sphere semimetals (NSSMs), featuring spherical band degeneracies in momentum space, constitute a fascinating class of topological materials. However, their realization in real materials is severely hampered by discrete crystallographic
symmetry constraints, often resulting in gapped “pseudo” nodal spheres. Here, combining first-principles calculations and
symmetry analysis, we predict a new three-dimensional boron allotrope, CT-B$_{24}$, as a nearly ideal NSSM. Its structural stability is systematically confirmed by
phonon calculations, ab initio molecular dynamics simulations at 600~K, and elastic constant analysis. Notably, the electronic structure of CT-B$_{24}$ exhibits two bands crossing linearly near the
Fermi level, forming a quasi-nodal sphere around the $\Gamma$ point. The maximum energy gap is merely 0.008~meV, which is two orders of magnitude smaller than the gaps reported in previous pseudo-NSSMs. Furthermore, the (001) surface hosts pronounced drumhead-like surface states located outside the projected nodal sphere, providing distinct signatures detectable by angle-resolved photoemission spectroscopy (ARPES). The nodal sphere also demonstrates remarkable robustness and tunability under external strain, driving a topological phase transition from an NSSM to a Dirac semimetal and finally to a trivial
insulator. Our work not only presents a superior material platform for exploring nodal-sphere physics but also suggests potential for strain-tunable topological devices.
Read the full abstract ▾
Strongly Correlated Electrons
KVASIR: A backscattering neutron spectrometer for hard condensed matter at ESS
Amalie F. Davidsen, Kristine M. L. Krighaar, Pascale P. Deen et al. (+1 more)
We present the instrument concept for KVASIR, a backscattering indirect time-of-flight
neutron spectrometer for the European Spallation Source (ESS). KVASIR will probe low lying excitations of single
crystal hard condensed matter that many advanced technologies rely upon. The instrument is simultaneously optimized for high resolution of energy-and momentum transfer, while ensuring perturbation by high
magnetic fields. Detailed ray tracing simulations, considering the true geometry and aberrations of the analyser configuration have been performed. The proposed concept has room for polarisation analysis and extreme sample environments. Inelastic
neutron scattering studies of single
crystal hard condensed matter, with a particular focus on
quantum, at yet unseen spatial and dynamic precision under extreme conditions are hereby enabled.
Read the full abstract ▾
All authors Amalie F. Davidsen, Kristine M. L. Krighaar, Pascale P. Deen, and Kim Lefmann
Statistical Mechanics · Cross-listed from hep-th
Multi-entropy from Linking in Chern-Simons Theory
Ma-Ke Yuan, Mingyi Li and Yang Zhou
We study the multipartite
entanglement structure of
quantum states prepared by the Euclidean path integral over three-
manifolds with multiple
torus boundaries (the so-called link states) in both Abelian and non-Abelian Chern-Simons theories. For three-component link states in the Abelian theory, we derive an explicit formula for the Rényi multi-
entropy in terms of linking numbers. We further show that the genuine multi-
entropy faithfully quantifies the tripartite
entanglement generated by GHZ-states, consistent with the fact that the prepared states are stabilizer states.
Read the full abstract ▾
Quantum Gases
Dynamically generating superflow in a bosonic ring via phase imprinting
Ke-Ji Chen and Fan Wu
Phase imprinting enables the dynamic generation of superflow in bosonic atoms, effectively overcoming traditional limitations such as
vortex number constraints and heating effects. However, the mechanisms underlying superflow formation remain insufficiently understood. In this work, we reveal these mechanisms by studying the time
evolution of the transferred total angular momentum and the quantized current throughout the phase imprinting process, achieved through numerically solving the time-dependent Schrödinger and Gross-Pitaevskii equations. We demonstrate that the Bose gas dynamically acquires angular momentum through the density depletion induced by the phase imprinting potential, whereas quantized currents emerge from azimuthal phase slips accompanied by complete density depletions. Regarding the impact of system parameters, such as interactions, we find that interactions hinder superflow formation, as the azimuthal density distribution becomes less susceptible to the phase imprinting potential. Our findings offer microscopic insights into the dynamic development of superflow during the phase imprinting process and provide valuable guidance for ongoing experimental efforts.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from quant-ph
Coherence-induced deep thermalization transition in random permutation quantum dynamics
Chang Liu, Matteo Ippoliti and Wen Wei Ho
We report a phase transition in the projected ensemble - the collection of post-measurement wavefunctions of a local subsystem obtained by measuring its complement. The transition emerges in systems undergoing random permutation dynamics, a type of
quantum time
evolution wherein computational basis states are shuffled without creating superpositions. It separates a phase exhibiting deep thermalization, where the projected ensemble is distributed over
Hilbert space in a maximally entropic fashion (Haar-random), from a phase where it is minimally entropic ("classical bit-string ensemble"). Crucially, this deep thermalization transition is invisible to the subsystem's density
matrix, which always exhibits thermalization to infinite-temperature across the phase diagram. Through a combination of analytical arguments and numerical simulations, we show that the transition is tuned by the total amount of coherence injected by the input state and the measurement basis, and is exhibited robustly across different microscopic models. Our findings represent a novel form of ergodicity-breaking universality in
quantum many-body dynamics, characterized not by a failure of regular thermalization, but rather by a failure of deep thermalization.
Read the full abstract ▾
Materials Science
Aqueous Preparation of CsPbBr3 Perovskite Nanocrystals Under Ambient Conditio
Zhaoyi Du, Jiewen Wei, Ding Ding et al. (+17 more)
Metal halide perovskites (MHPs) have had a profound impact on numerous emerging optoelectronic technologies, achieving performance metrics that rival or exceed incumbent materials. This impact is underpinned by the exceptional properties of MHPs, including tuneable band gaps, high absorption coefficients, long carrier
diffusion lengths and combined with uncomplicated synthesis methods. However, current MHP production relies on the toxic solvents, which pose significant environmental and health risks. Moreover, these methods often require complex multi component solvent systems and thermal processing to achieve the desired material phases, further hindering scalability and sustainability. Overcoming these challenges is critical to the future development of MHP-based technologies. Overcoming these challenges is critical to the future development of MHP-based technologies. Here, we present a novel water-based solvent system and synthetic approach for the preparation of size-controlled CsPbBr3 perovskite nanocrystals in ambient air and at room temperature. The photoluminescence
quantum yield (PLQY) of CsPbBr3 erovskite nanocrystals (PNCs) exceeds 60 precent. To demonstrate the light to current conversion ability of our PNCs a series of photoconductors were prepared, with the best performing devices achieving a specific detectivity (D*) of 1.2 x 10^11 Jones. Thus, this green, scalable, and low-cost approach offers a sustainable pathway for precise size and compositional control of MHP nanocrystals, opening new possibilities for environmentally friendly optoelectronic applications.
Read the full abstract ▾
All authors Zhaoyi Du, Jiewen Wei, Ding Ding, Martina Rimmele, Yueyao Dong, Weitao Qian, Davide Nodari, Francesco Furlan, Edoardo Angela, George Morgan, Peter Akinshin, William Rodriguez Kazeem, Gwilherm Kerherve, Adam V. Marsh, Martin Heeney, Thomas J. Macdonald, Saif A. Haque, Nicola Gasparini, David J. Payne, Martyn A. McLachlan
Statistical Mechanics · Cross-listed from quant-ph
Haruki Yagi and Zongping Gong
A rigorous analysis is presented for the
entanglement spectrum of
quantum many-body states possessing a higher-form group-representation
symmetry generated by topological Wilson loops, which is generally non-invertible. A general framework based on elementary algebraic
topology and category theory is developed to determine the block structure of reduced density
matrices for arbitrary bipartite
manifolds on which the states are defined. Within this framework, we scrutinize the impact of
topology on the
entanglement structure for low-dimensional
manifolds, including especially the
torus, the Klein bottle, and lens spaces. By further incorporating gauge invariance, we refine our framework to determine the
entanglement structure for topological gauge theories in arbitrary dimensions. In particular, in two dimensions, it is shown for the Kitaev
quantum double model that not only the topological
entanglement entropy can be reproduced, but also the Li-Haldane
conjecture concerning the full
entanglement spectrum holds exactly.
Read the full abstract ▾
Materials Science
Chemical States and Local Structure in Cu-Deficient CuInSe2 Thin Films: Insights into Engineering and Bandgap Narrowing
Ahmed Yousef Mohamed, Byoung Gun Han, Hyeonseo Jang et al. (+6 more)
The Cu-deficient CuxInSe2 (x larger than 0.3) phase can be stabilized as a thin film. A uniform Cu-deficient composition with a chalcopyrite structure was obtained by the precision engineering of a two-step synthesis process involving electron-beam evaporation and Se vapor deposition. Detailed structural and chemical analyses were performed employing various X-ray and microscopic techniques to demonstrate that the chemical states and local structure in the Cu-Se-In tetrahedral networks change with the loss of Cu, the In-Se bond becomes shorter, and the In ions become excessively oxidized without phase separation. Moreover, the results indicate that the bandgap narrowing is primarily attributed to the reconstruction of In3+d 5s orbital states. The bandgap narrows from 1.51 eV to 1.4 eV, which is optimal for the
photon absorber. Therefore, cation-deficient selenide is promising for stable nontoxic photovoltaics with tunable bandgaps.
Read the full abstract ▾
All authors Ahmed Yousef Mohamed, Byoung Gun Han, Hyeonseo Jang, Jun Oh Jeon, Yejin Kim, Haeseong Jang, Min Gyu Kim, Kug-Seung Lee, Deok-Yong Cho
Materials Science
GoodRegressor: A Hierarchical Inductive Bias for Navigating High-Dimensional Compositional Space
Seong-Hoon Jang
Interpretable scientific machine learning often trades predictive performance for structural transparency. When physical targets arise from hierarchical and nonlinear descriptor
entanglement, weakly interacting white-box models underfit, whereas highly expressive black-box models obscure physical insight. Here I introduce GoodRegressor, a hierarchical depth-controlled symbolic regression framework that systematically assembles nonlinear descriptor interactions through lexicographically-ordered expansion. Despite effective compositional search spaces approaching $\sim 10^{400}$ structures, disciplined depth control enables tractable and reproducible exploration under realistic computational constraints. Across oxygen-ion conductors, NASICONs, and superconducting
oxides, as representative high-complexity testbeds, predictive performances match or exceed state-of-the-art black-box models, retaining explicit functional form. Moreover, interaction-depth
evolution reveals system-dependent optimal windows, providing an empirical taxonomy of hierarchical complexity in scientific
datasets. These results establish hierarchical inductive bias with explicit depth control as a design principle for interpretable artificial intelligence in high-dimensional compositional spaces, and position interaction depth as a structural axis for diagnosing hierarchical complexity in scientific systems.
Read the full abstract ▾
Materials Science
Floquet engineering enabled by charge density wave transition
Fei Wang, Xuanxi Cai, Teng Xiao et al. (+10 more)
Floquet engineering has emerged as a powerful approach for dynamically tailoring the electronic structures of
quantum materials through time-periodic light fields generated by ultrafast
laser pulses. The light fields can transiently dress Bloch electrons, creating novel electronic states inaccessible in
equilibrium. While such temporal modulation provides dynamic control, spatially periodic modulations, such as those arising from charge density wave (CDW) order, can also dramatically reconstruct the band structure through real-space
symmetry breaking. The interplay between these two distinct forms of modulation-temporal and spatial-opens a new frontier in electronic-phase-dependent Floquet engineering. Here we demonstrate this concept experimentally in the prototypical CDW material 1T-TiSe$_2$. Using time- and angle-resolved photoemission spectroscopy (TrARPES) with mid-infrared pumping, we observe a striking pump-induced instantaneous downshift of the valence band maximum (VBM), which is in sharp contrast to the subsequent upward shift on picosecond timescale associated with CDW melting. Most remarkably, the light-induced VBM downshift is observed exclusively in the CDW phase and only when the pump pulse is present, reaching maximum when pumping near resonance with the CDW gap. These observations unequivocally reveal the critical role of CDW in the Floquet engineering of TiSe$_2$. Our work demonstrates how time-periodic drives can synergistically couple to spatially periodic modulations to create non-
equilibrium electronic states, establishing a new paradigm for Floquet engineering enabled by spontaneous
symmetry breaking.
Read the full abstract ▾
All authors Fei Wang, Xuanxi Cai, Teng Xiao, Changhua Bao, Haoyuan Zhong, Wanying Chen, Tianyun Lin, Tianshuang Sheng, Xiao Tang, Hongyun Zhang, Pu Yu, Zhiyuan Sun, Shuyun Zhou
Statistical Mechanics
Fluctuations in first passage times and utility of resetting protocol in biochemical systems with two-state toggling
Hillol Kumar Barman, Pathik Das and Syed Yunus Ali
Interesting theoretical problems of target search or threshold crossing, formally known as first passage, often arise in both diffusive transport problems as well as problems of chemical reaction kinetics. We study three systems following different chemical kinetics, and are special as they toggle between two states: (i) a population dynamics of
cells with auto-catalytic birth and intermittent toxic chemical-induced forced death, (ii) a bond cluster model representing membrane adhesion to extracellular
matrix under a fluctuating load, and (iii) a model of gene transcription with a regulated promoter switching between active and inactive states. Each of these systems has a target state to attain, which defines a first passage problem – namely, population becoming extinct, complete membrane detachment, or mRNA count crossing a threshold. We study the fluctuations in first passage time and show that it is interestingly non-monotonic in all these cases, with increasing strength of bias towards the target. We also study suitable
stochastic resetting protocols to expedite first passage for these systems, and show that there is a re-entrant transition of the efficacy of this protocol in all the three cases, as a function of the bias. The exact analytical condition for these transitions predicted in earlier literature is verified here through simulations.
Read the full abstract ▾
Statistical Mechanics · Cross-listed from quant-ph
Information geometry of nonmonotonic quantum natural gradient
Hideyuki Miyahara
Natural gradient is an advanced optimization method based on information geometry, where the Fisher metric plays a crucial role. Its
quantum counterpart, known as
quantum natural gradient (QNG), employs the symmetric logarithmic derivative (SLD) metric, one of the
quantum Fisher metrics. While quantization in physics is typically well-defined via the canonical commutation relations, the quantization of information-theoretic quantities introduces inherent arbitrariness. To resolve this ambiguity, monotonicity has been used as a guiding principle for constructing geometries in physics, as it aligns with physical intuition. Recently, a variant of QNG, which we refer to as nonmonotonic QNG in this paper, was proposed by relaxing the monotonicity condition. It was shown to achieve faster convergence compared to conventional QNG. In this paper, we investigate the properties of nonmonotonic QNG. To ensure the paper is self-contained, we first demonstrate that the SLD metric is locally optimal under the monotonicity condition and that non-monotone
quantum Fisher metrics can lead to faster convergence in QNG. Previous studies primarily relied on a specific type of
quantum divergence and assumed that density operators are full-rank. Here, we explicitly consider an alternative
quantum divergence and extend the analysis to non-full-rank cases. Additionally, we explore how geometries can be designed using Petz functions, given that
quantum Fisher metrics are characterized through them. Finally, we present numerical simulations comparing different
quantum Fisher metrics in the context of parameter estimation problems in
quantum circuit learning.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Spin gaps in Transition Metal Dichalcogenide Nanoribbons with atomic Adsorbates
Joshua O. Aggrey, Leonard Bleiziffer and Frank Hagelberg
Edge-functionalized Transition Metal dichalcogenide nanoribbons of the zigzag type (zTMDCNRs) are explored in terms of their
spin transmission properties. Specifically, systems of the type 5-zWXYNR + nA (X, Y = S, Se; n = 0, 1, 2; A = H, B, C, N, O), involving five rows of a zWXY unit, are investigated as transmission elements between semi-infinite electrodes, to identify atomic adsorbates and adsorption conditions for maximizing the
spin polarization of current traversing the ribbons. Janus counterparts of these units, asymmetric structures comprising a transition metal layer sandwiched by two different chalcogen layers, are included in this study. In all cases considered, density functional theory (DFT) modeling, involving the hybrid Heyd-Scuseria-Ernzerhof (HSE) exchange-correlation functional, is combined with the non-
equilibrium Green's function (NEGF) approach to determine both
spin and charge transport properties. The effect of the selected atomic absorbates on the
geometric, electronic, and
magnetic properties of 5-zWXYNR (X, Y = S, Se) is evaluated. A protocol to assess the
spin-filtering capacity of 5-zWXYNR + nad as a function of the nature and the density of atomic adsorbates, is formulated in terms of band structure analysis of the respective electrode units.
Spin gaps emerging close to the
Fermi energy of the electrode are shown to provide an effective predictor for the degree of current
spin polarization achieved by any of the transmission systems studied here. For any adsorbate configuration considered,
ferromagnetic (FM) as well as
antiferromagnetic (AFM) ordering is examined, and the impact of the
magnetic phase on the
spin transport properties is discussed. A
spin-selective negative differential resistance effect is identified for specific nanoribbon systems.
Read the full abstract ▾