Mesoscale and Nanoscale Physics
Wiener-Hopf factorization and non-Hermitian topology for Amoeba formulation in one-dimensional multiband systems
Shin Kaneshiro and Robert Peters
The non-Hermitian skin effect (NHSE), characterized by the extensive localization of bulk modes at the boundaries, has attracted significant
attention as a hallmark feature of non-Hermitian
topology. This localization invalidates the conventional Bloch band theory, necessitating an analysis under open boundary conditions even in the thermodynamic limit. The Amoeba formulation addresses this challenge by computing the spectral potential rather than the spectrum itself. Based on the (strong) Szegö limit
theorem and its topological generalization, this approach reduces the evaluation of the potential to an optimization problem involving the Ronkin function. However, while the generalized Szegö limit
theorem is formally applicable in arbitrary dimensions, its implementation is limited to single-band systems, and its applicability to multiband systems remains unclear even in one-dimensional systems. In this paper, we establish the Wiener-
Hopf factorization (WHF) of the non-Bloch
Hamiltonian as a powerful framework, providing a unified and rigorous foundation for Amoeba analysis in one-dimensional multiband systems. By combining the WHF with Hermitian doubling, we first elucidate the applicability criteria for the generalized Szegö limit
theorem in multiband systems. We then show that the WHF provides the natural mathematical origin for the
symmetry-decomposed Ronkin function in
symmetry class AII$^\dagger$, leading to a rigorous proof of the generalized Szegö limit
theorem for these systems and opening a path toward systematic generalizations to other
symmetry classes.
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Strongly Correlated Electrons · Cross-listed from hep-th
Global symmetries: locality, unitarity, and regularity
Ibrahima Bah, Shlomo S. Razamat, Michal Shemesh et al. (+1 more)
We study the apparent tension between locality and unitarity for
symmetries in
quantum field theory. This emerges in the context of categorical
symmetries where
symmetry operators are generically non-invertible. We argue that locality imposes particular regularities in the action of
symmetries on the
Hilbert space. This allows us to introduce an observable that can measure the properties of the non-locality for
symmetry operators. We study it for a class of examples and demonstrate that this observable can encode data associated to the fusion
algebra of
symmetries.
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All authors Ibrahima Bah, Shlomo S. Razamat, Michal Shemesh, Hannah Tillim
Mesoscale and Nanoscale Physics
Fokker-Planck approach to thermal fluctuations in antiferromagnetic systems
E. Martello, G. A. Falci, E. Paladino et al. (+1 more)
We develop a Fokker-Planck approach to describe the dynamics of staggered magnetization and thermal fluctuations in a two-dimensional
antiferromagnetic system with uniaxial anisotropy. Beginning with a classical model for the
antiferromagnetic system, we incorporate a Landau-Lifshitz-Gilbert equation augmented by Langevin fields to account for thermal fluctuations, and we derive the Fokker-Planck equation governing the probability distribution function of the
spin configuration. Employing the mean-field approximation, we derive the equations of motion for the
spin polarization and the two-time
spin-
spin correlation functions. The methodology is applied to the study of
spin-wave dynamics and to the formulation of a phenomenological model for resistance fluctuations in two-dimensional
antiferromagnetic semiconductors.
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All authors E. Martello, G. A. Falci, E. Paladino, F. M. D. Pellegrino
Statistical Mechanics
Scaling of free cumulants in closed system-bath setups
Merlin Füllgraf, Jochen Gemmer and Jiaozi Wang
The Eigenstate Thermalization Hypothesis (ETH) has been established as a cornerstone for understanding thermalization in
quantum many-body systems. Recently, there has been growing interest in the full ETH, which extends the framework of the conventional ETH and postulates a smooth function to describe the multi-point correlations among
matrix elements. Within this framework, free cumulants play a central role, and most previous studies have primarily focused on closed systems. In this paper, we extend the analysis to a system-bath setup, considering both an idealized case with a random-
matrix bath and a more realistic scenario where the bath is modeled as a defect Ising chain. In both cases, we uncover a universal scaling of the microcanonical free cumulants of observables associated with the central system
Hamiltonian with respect to the interaction strength. Furthermore we establish a connection between this scaling behavior and the thermalization dynamics of the thermal free cumulants of corresponding observables.
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Superconductivity
Interpretable descriptors enable prediction of hydrogen-based superconductors at moderate pressures
Jiawei Chen, Junhao Peng, Yanwei Liang et al. (+3 more)
Room temperature superconductivity remains elusive, and hydrogen-base compounds despite remarkable transition temperatures(Tc) typically require extreme pressures that hinder application. To accelerate discovery under moderate pressures, an interpretable framework based on symbolic regression is developed to predict Tc in hydrogen-based
superconductors. A key descriptor is an integrated density of states (IDOS) within 1 eV of the
Fermi level (EF), which exhibits greater robustness than conventional single-point DOS features. The resulting analytic model links electronic-structure characteristics to superconducting performance, achieves high accuracy (RMSEtrain = 20.15 K), and generalizes well to external
datasets. By relying solely on electronic structure calculations, the approach greatly accelerates materials screening. Guided by this model, four hydrogen-based candidates are identified and validated via calculation: Na2GaCuH6 with Tc =42.04 K at ambient pressure (exceeding MgB2), and NaCaH12, NaSrH12, and KSrH12 with Tc up to 162.35 K, 86.32 K, and 55.13 K at 100 GPa, 25 GPa, and 25 GPa, respectively. Beyond rapid screening, the interpretable form clarifies how hydrogen-projected electronic weight near EF and related features govern Tc in hydrides, offering a mechanism-aware route to stabilize high-Tc phases at reduced pressures.
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All authors Jiawei Chen, Junhao Peng, Yanwei Liang, Renhai Wang, Huafeng Dong, Wei Zhang
Mesoscale and Nanoscale Physics
Impact of spin-orbit coupling and Zeeman interaction on the multiple Andreev reflections subharmonic gap structure in nanoscopic Josephson junctions
D. Kuiri, J. H. Correa, A. Biborski et al. (+1 more)
Multiple Andreev reflections in voltage-biased Josephson junctions give rise to the subharmonic gap structure in the conductance, which is widely used to characterize transport properties and estimate the induced gap in the junctions. Here we theoretically investigate the
evolution of the subharmonic gap structure in spinful Josephson junctions.
Spin mixing introduced by the
spin-orbit coupling opens avoided crossings in the dispersion relation of the leads, which, as we demonstrate, subsequently results in pronounced multiple Andreev reflection features in the conductance traces. We analyze how these features evolve under an external
magnetic field and explain that their visibility in conductance is governed by the
spin polarization of the bands.
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All authors D. Kuiri, J. H. Correa, A. Biborski, M. P. Nowak
Mesoscale and Nanoscale Physics
Orbital Accumulation Induced by Chiral Phonons
Tetsuya Sato, Takeo Kato and Aurelien Manchon
We theoretically investigate orbital accumulation driven by
chiral phonons via orbital-dependent electron-
lattice coupling. We derive a formula for the orbital accumulation induced by classical
lattice dynamics or nonequilibrium
phonons, emphasizing the rectified second-order response of the orbital moment to
lattice displacement. We show that
chiral phonons primarily couple to orbital quadrupole moments and that static orbital dipole accumulation can be generated at second order in the
lattice displacement. Our study provides a useful method for generating orbital accumulation without using
spin-orbit interactions and suggests a strategy to boost its magnitude by harnessing band structure hot spots associated with orbital degeneracy.
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Superconductivity
Multiple correlation lengths and type-1.5 superconductivity in $U(1)$ superconductors due to hidden competition between irreducible representations of nonlocal pairing
Anton Talkachov, Paul Leask and Egor Babaev
A fundamental characteristic of a superconducting state is the coherence length $\xi$. Multicomponent
superconductors, particularly ones breaking multiple
symmetries, are characterized by multiple coherence lengths. Here we show that even, nominally $single$-component
superconductors under certain conditions are characterized by multiple coherence lengths. We consider nearest-neighbor pairing interactions on a square
lattice that leads to $s$-wave and $d$-wave representations of link superconducting order parameter. We show that even if the subdominant order parameter is completely suppressed in the ground state, it results in multiple correlation lengths with nontrivial hierarchy, resulting in important physical consequences in inhomogeneous solutions. Under certain conditions, this leads to type-1.5 superconductivity, where
magnetic field penetration length falls between two coherence lengths, leading to
vortex clustering in an external
magnetic field.
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Mesoscale and Nanoscale Physics
Topological states and flat bands in exactly solvable decorated Cayley trees
Wanda P. Duss, Askar Iliasov and Tomáš Bzdušek
We derive the full spectrum of decorated Cayley trees that constitute tree analogs of selected two-dimensional Euclidean
lattices; namely of the Lieb, the double Lieb, the kagome, and the
star lattice. The common feature of these Euclidean
lattices is that their nearest-neighbor models give rise to flat energy bands interpretable through compact localized states. We find that the tree analogs exhibit similar flat or nearly flat energy bands at the corresponding energies. Interestingly, such flat bands in the decorated Cayley trees acquire an interpretation that is absent in their Euclidean counterparts: as edge states localized to the inner or the outer boundary of the tree branches. In particular, we establish an exact correspondence between the Lieb-Cayley tree and an ensemble of one-dimensional Su-Schrieffer-Heeger chains, which maps topological edge states on one side of the chains to flat-band states localized in the bulk of the tree, furnishing the flat energy band with a topological stability. Similar mapping to topological edge states or to states bound to edge defects in one-dimensional chains is shown for flat-band states in all the considered tree decorations. We finally show that the persistence of exact flat bands on infinite decorated trees (i.e., Bethe
lattices) arises naturally from a covering interpretation of tree graphs. Our findings reveal a rich landscape of flat-band and topological phenomena in non-Euclidean systems, where geometry alone can generate and stabilize unconventional
quantum states.
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Materials Science
Electronic and magnetic properties of light rare-earth cubic Laves compounds derived from XMCD experiments
Vilde G. S. Lunde, Benedicte S. Ofstad, Øystein S. Fjellvåg et al. (+4 more)
This work presents electronic and
magnetic properties of selected members in the cubic Laves phase series Nd1-xPrxCoNi and Ce0.25Pr0.75CoNi, together with the corresponding binary compositions (NdCo2, NdNi2, PrCo2, PrNi2, CeCo2, CeNi2), using soft x-ray absorption spectroscopy, x-ray
magnetic circular dichroism (XMCD), density-functional theory, and
crystal field multiplet calculations. All transition-metal moments saturate below 1 T, while the rare-earth moments do not saturate even at 5 T, consistent with van Vleck paramagnetic contributions and
crystal field suppression. While the sum rules are widely used to extract element-specific
magnetic moments from XMCD, we show that for 3d transition metals, their application requires accurate estimates of the number of unoccupied 3d states. We observe a finite
magnetic moment on Ni, challenging the common assumption of its nonmagnetic character in Laves phases. The orbital
magnetic moments were determined using the
spin rules, while the
spin moments were estimated from single-ion values from multiplet calculations, due to the invalidity of the
spin sum rule for light rare-earth elements. The
magnetic moments of Nd and Pr are found to be suppressed relative to their free-ion values, with multiplet theory indicating that this is due to
crystal field effects. Our results confirm that Nd and Pr maintain localized 4f3 and 4f2 configurations, respectively, and that their element-specific
magnetic moments are robust to rare-earth substitution. Ce, on the other hand, exhibits a tunable mixed-valent ground state with both
magnetic 4f1 and nonmagnetic 4f0 components. The relative fraction of these states varies with the electronegativity of the surrounding 3d transition metals, revealing a pathway to tune Ce magnetism via composition. This work establishes a framework for accurately interpreting XMCD in light rare-earth-based intermetallics.
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All authors Vilde G. S. Lunde, Benedicte S. Ofstad, Øystein S. Fjellvåg, Philippe Ohresser, Anja O. Sjåstad, Bjørn C. Hauback, Christoph Frommen
Soft Condensed Matter
From LRO to Disorder via QLRO in Spatially Inhomogeneous Polar Flock
Anish Kumar, Vivek Semwal and Shradha Mishra
We study the collective behavior of a polar flock in an inhomogeneous environment in two-dimensions. The inhomogeneity is modelled by introducing regions at random locations on the substrate with higher noise but accessible for the flock to move. Hence inside such regions the particles orientation get randomised. Such inhomogeneities are different from the physical disorder, which obstructs the space for the incoming particles. The study focuses on how the phase behavior of polar flock changes by tuning the packing fraction of inhomogeneity. As packing fraction increases, the system crosses over from long-range to quasi long range order and ultimately to a disordered phase, while the order disorder transition for flocking changes from discontinuous to continuous. The resultant phase behavior of polar flock patterns here is comparable to that exhibited in the presence of physical disorder.
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Superconductivity
Topological Theory of Helium 4
Leonid Lantsman
In this paper we attempt to construct the topological theory of superfluid helium $4$ in the framework of the (rigid) $U(1)$ model in which the initial $U(1)$ group is destroyed with appearance of (topologically nontrivial) domains separated by domain walls treated as step voltages between domains (e.g. with neighboring topological numbers). This can explain the superfluid properties in a helium $4$ specimen as well as the appearance of topologically nontrivial
vortices therein.
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Materials Science
Potential-Barrier Affinity Effect in Solid Systems
Qiang Xu, Zhao Liu and Yanming Ma
Electron accumulation in interatomic regions is a fundamental
quantum phenomenon dictating chemical bonding and material properties, yet its origin remains elusive across disciplines. Here, we report a
quantum accumulation effect – potential-barrier affinity (PBA) – revealed by solving the Schrödinger equation for a crystalline potential. PBA effect drives significant interatomic electron accumulation when electron energy exceeds the barrier maximum. This effect essentially enhances interatomic electron density, governing microstructures and properties of condensed matter. Our theory overturns the traditional wisdom that the interstitial electron localization in electride requires potential-well constraints or hybrid orbitals, and it serves as the fundamental mechanism underlying the formation of conventional solid bonding. This work delivers a paradigm shift in understanding electron distribution and establishes a theoretical foundation for the microscopic design of material properties.
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Soft Condensed Matter
Models for active particles: common features and differences
Colin-Marius Koch and Michael Wilczek
Systems of active particles can show a large variety of collective behavior. In theory, two aspects determine the collective behavior: the model at the particle level and the parameter regime. While many studies consider a single model and study its parameter regime, here, we focus on the former aspect. Motivated by experiments that study dilute suspensions of Chlamydomonas reinhardtii in a self-generated oxygen gradient, we compare various models with external field-dependent motility to understand how the collective behavior changes between models. We vary the particle-particle interaction from no interactions to steric interactions, the particle shape from round disks to dumbbells, the self-propulsion mechanism from constant speed to rocking motion, and the particle's center of mass from the
geometric center to off-center. We find that changes in the model of the active
agents can lead to similar statistics in the dilute regime and different collective behavior in the dense regime. We conclude that active particle models do not easily generalize for different real active
agents, but instead require a clear understanding of the
agents' microscopic properties.
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Disordered Systems and Neural Networks
Nonequilibrium Thermodynamics of Associative Memory Continuous-Time Recurrent Neural Networks
Miguel Aguilera, Daniele De Martino, Ivan Garashchuk et al. (+1 more)
Continuous-Time Recurrent Neural Networks (CTRNNs) have been widely used for their capacity to model complex temporal behaviour. However, their internal dynamics often remain difficult to interpret. In this paper, we propose a new class of CTRNNs based on Hopfield-like associative
memories with asymmetric couplings. This model combines the expressive power of associative
memories with a tractable mathematical formalism to characterize fluctuations in nonequilibrium dynamics. We show that this mathematical description allows us to directly compute the
evolution of its macroscopic observables (the encoded features), as well as the instantaneous
entropy and
entropy dissipation of the system, thereby offering a bridge between dynamical systems descriptions of low-dimensional observables and the statistical mechanics of large nonequilibrium networks. Our results suggest that these nonequilibrium associative CTRNNs can serve as more interpretable models for complex sequence-encoding networks.
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All authors Miguel Aguilera, Daniele De Martino, Ivan Garashchuk, Dmitry Sinelshchikov
Materials Science
Tunable electronic band structure in WSSe van der Waals Alloys
Meryem Bouaziz, Leonard Schue, Noeliarinala Felana Andriambelaza et al. (+12 more)
The electronic structure of semiconducting 2D materials such as transition metal dichalcogenides (TMDs) is known to be tunable by its environment, from simple external fields applied with electrical contacts up to complex van der Waals
heterostructure assemblies. However, conventional alloying from reference binary TMD compounds to composition-controlled ternary
alloys also offers unexplored opportunities. In this work, we use nano-angle resolved photoemission spectroscopy (nano-ARPES) and density functional theory (DFT) calculations to study the structural and electronic properties of different
alloy compositions of bulk WS2(1-x)Se2x. Our results demonstrate the continuous variation of the band structure and the progressive
evolution of the valence band splitting at the K points from 420 to 520 meV in bulk WS2(1-x)Se2x. We also carried out scanning tunneling microscopy (STM) measurements and DFT to understand the possible S or Se substitutions variants in WS2(1-x)Se2x
alloys, with different local atomic configurations. Our work opens up perspectives for the fine control of the band dispersion in van der Waals materials and demonstrate how the band structure can be tuned in bulk TMDs. The collected information can serve as a reference for future applications.
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All authors Meryem Bouaziz, Leonard Schue, Noeliarinala Felana Andriambelaza, Natalia Alyabyeva, Jean-Christophe Girard, Pavel Dudin, Fabian Cadiz, Jose Avila, Yannick Dappe, Cesar Gonzalez, Julien Chaste, Fabrice Oehler, Christine Giorgetti, Fausto Sirotti, Abdelkarim Ouerghi
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Perovskite Nanocrystals as Emerging Single-Photon Emitters: Progress, Challenges, and Opportunities
Jehyeok Ryu, Victor Krivenkov, Adam Olejniczak et al. (+2 more)
Metal-halide perovskite nanocrystals (PNCs) have emerged as leading candidates for next-generation
quantum emitters, offering a unique combination of high photoluminescence
quantum yield, tunable emission, short radiative lifetimes, and record-high single-
photon purity under ambient conditions. These properties, together with low-cost and scalable solution-phase fabrication, position PNCs as attractive alternatives to traditional epitaxial and colloidal
quantum dots. In this Review, we outline the physical parameters that define
quantum emission in PNCs, compare their performance to other established and emerging
quantum emitters, and assess the key figures of merit, including photostability, single-
photon purity, and
photon indistinguishability, required for practical
quantum applications. We discuss underlying mechanisms affecting PNC emission behavior and highlight recent advances in improving their
quantum emitting properties through synthetic and photonic engineering approaches. While challenges related to environmental stability and
photon indistinguishability remain, emerging strategies, such as surface passivation, metal ion doping, and coupling with electromagnetic nano- and micro-cavities, are steadily closing the gap between PNCs and ideal
quantum light sources.
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All authors Jehyeok Ryu, Victor Krivenkov, Adam Olejniczak, Alexey Y. Nikitin, Yury Rakovich
Materials Science
Field-tunable partial antiferromagnetism, glassy spin dynamics, and magnetodielectric coupling in the quasi-one-dimensional spin-chain compound Ca3CoIrO6
Priyanka Mahalle, A. Kumar, Kumar Bharti et al. (+3 more)
We report a comprehensive investigation of the quasi-one-dimensional
spin-chain compound Ca3CoIrO6 (CCIO) using a combination of structural,
magnetic, thermodynamic, transport, Raman, and dielectric measurements. Temperature-dependent
neutron powder diffraction confirms the rhombohedral R-3c structure down to 5 K without any structural phase transition. DC magnetization, ac susceptibility, and relaxation measurements reveal a gradual
evolution from a high-temperature paramagnetic-like state to a partially disordered
antiferromagnetic (PDA) state below 100 K, accompanied by slow cluster-like
spin dynamics followed by a freezing transition near 30 K. Isothermal
magnetic hysteresis M(H) loops demonstrate partial chain freezing, while robust exchange bias is observed in field-cooled protocols, highlighting the interplay between PDA ordering and frozen
spins. Resistivity and specific heat data indicate strong coupling between
spin and charge degrees of freedom, accompanied by activated transport behavior. Raman spectroscopy identifies pronounced anomalies in
phonon frequencies and linewidths across multiple
magnetic regimes, reflecting strong
spin-
lattice coupling. Polarization-electric field (P-E) measurements reveal temperature-dependent crossovers from linear dielectric to weakly hysteretic behavior, consistent with short-range polar correlations driven by
spin-
lattice interactions. These findings establish CCIO as a prototypical quasi-one-dimensional frustrated
spin-chain system where
geometric frustration,
spin-orbit coupling, and low-dimensionality generate field-tunable PDA order, glassy
spin dynamics, exchange bias, and magnetodielectric coupling. These results provide new insights into frustration-driven phases in low-dimensional
oxides and point towards potential multifunctional applications based on intrinsic magnetodielectric and exchange bias phenomena.
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All authors Priyanka Mahalle, A. Kumar, Kumar Bharti, Dipanshu Bansal, P. D. Babu, S. M. Yusuf
Superconductivity
Optical Properties of Superconducting K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ Single Crystals
Andrei Muratov, Yevgeny Rakhmanov, Andrei Shilov et al. (+2 more)
The optical properties of the superconducting K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ single
crystals with a critical temperature $T_c\approx 26$ K have been measured in the ab plane in a wide frequency range using both infrared
Fourier-transform spectroscopy and spectroscopic ellipsometry at temperatures of 4–300 K. The normal-state reflectance of K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ is analyzed using a Drude-Lorentz model with one Drude component. The temperature dependences of the
plasma frequency, optical conductivity, scattering rate, and dc resistivity of the Drude contribution in the normal state are presented. In the superconducting state, we observe a signature of the superconducting gap opening at $2\Delta $(5~K) = 11.8~meV. An abrupt decrease in the low-frequency dielectric permittivity $\varepsilon _1(\omega )$ at $T < T_c$ also evidences the formation of the superconducting condensate. The superconducting
plasma frequency $\omega _{pl,s} = (213\pm 5)$~cm$^{-1}$ and the
magnetic penetration depth $\lambda =(7.5\pm 0.2)$~$\mu $m at $T=5$~K are determined.
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All authors Andrei Muratov, Yevgeny Rakhmanov, Andrei Shilov, Igor Morozov, Yurii Aleshchenko
Soft Condensed Matter
First-passage statistics of confined colloids
Guirec de Tournemire, Nicolas Fares, Yacine Amarouchene et al. (+1 more)
The encounter of diffusing entities underlies a wide range of natural phenomena. The dynamics of these first-passage dynamics are strongly influenced by confining geometries. Confinement modifies microscopic
diffusion through conservative and hydrodynamic interactions, making it essential for realistic modeling. In this Letter, we investigate how confinement affects the first-passage statistics of a diffusing particle. Using state-of-the-art
holographic microscopy combined with advanced statistical inference, we probe this motion with nanometric precision. Our experimental and numerical results show that confinement can either hinder or enhance first-passage kinetics, depending on the spatial direction. In particular, wall-normal target finding is accelerated by confinement-induced non-Gaussian displacement statistics, which increases the probability of rare, large displacements, with implications for confined chemical reactions and biological winners-take-all processes near boundaries.
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All authors Guirec de Tournemire, Nicolas Fares, Yacine Amarouchene, Thomas Salez
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Ligand Engineering for Precise Control of Ultrathin CsPbI3 Nanoplatelet Superlattices for Efficient Light-Emitting Diodes
Jongbeom Kim, Woo Hyeon Jeong, Junzhi Ye et al. (+17 more)
Strongly-confined perovskite nanoplatelets (PeNPLs) offer opportunities not found in conventional isotropic nanocubes, especially in producing linearly polarized light, as well as enhancing outcoupling through control over the transition dipole moment. But this requires ultrathin nanoplatelets with three or fewer monolayers of PbI6 octahedra across the thickness, which are challenging to synthesise uniformly, and their luminescence is strongly affected by surface defects. Together, these limit the performance of ultrathin PeNPLs in light-emitting diodes (LEDs). Here, we address these challenges with an ancillary ligand engineering strategy. We demonstrate that ligands with phosphoryl functional groups strongly bind to the perovskite surface, while having an organic backbone that is not sterically bulky ensures high ligand density. By modulating nucleation and growth, these ancillary ligands lead to monodisperse PeNPLs that stack more uniformly when self-assembled into superlattices, with suppressed agglomeration. As a result, from edge-up PeNPL superlattices, we achieve enhanced degree of polarization, while from face-down PeNPL superlattices, we achieve enhanced outcoupling that results in LEDs with 13.1% external
quantum efficiency, the highest reported for ultrathin PeNPL LEDs. This work establishes ancillary ligand-induced synthesis as a decisive route to achieve uniform nanoplatelets with robust orientation control, enabling full utilization of the multifunctionality of anisotropic PeNPLs.
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All authors Jongbeom Kim, Woo Hyeon Jeong, Junzhi Ye, Allison Nicole Arber, Vikram, Donghan Kim, Yi-Teng Huang, Yixin Wang, Dongeun Kim, Dongryeol Lee, Chia-Yu Chang, Xinyu Shen, Sung Yong Bae, Ashish Gaurav, Akshay Rao, Henry J. Snaith, M. Saiful Islam, Bo Ram Lee, Myoung Hoon Song, Robert L. Z. Hoye
Strongly Correlated Electrons
Optical conductivity of layered topological semimetal TaNiTe$_5$
Jakov Budić, Serena Nasrallah, D. Santos-Cottin et al. (+9 more)
We present an infrared spectroscopy study of the layered topological semimetal TaNiTe$_5$, a material with a quasi-one-dimensional structure and strong in-plane anisotropy. Despite its structural features, infrared reflectivity and electronic transport measurements along the $a$ and $c$ crystallographic axes show metallic behavior without evidence of reduced dimensionality. Optical conductivity reveals an anisotropic but conventional metallic response with low scattering rates and a single sharp infrared-active
phonon mode at $396$ cm$^{-1}$ ($49$ meV). Ab initio calculations closely match the experimental optical data and confirm a three-dimensional electronic structure. Our results demonstrate that TaNiTe$_5$ behaves as a three-dimensional anisotropic semimetal in its electronic and optical properties.
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All authors Jakov Budić, Serena Nasrallah, D. Santos-Cottin, F. Le Mardelé, A. Pulkkinen, J. Minár, P. Sačer, B. Gudac, N. Barišić, C. C. Homes, Ana Akrap, Mario Novak
Soft Condensed Matter
Emergent Synchronization and Defect Dynamics in Confined Chiral Active Suspensions
Zaiyi Shen, Leilei Wang, Shishuang Zhang et al. (+4 more)
Hydrodynamic interactions can generate rich emergent structures in active matter systems. Using large-scale hydrodynamic simulations, we demonstrate that hydrodynamic coupling alone can drive spontaneous self-organization across a hierarchy of spatial and temporal scales in confined suspensions of torque-driven particles at moderate Reynolds numbers. Spinners first self-assemble into dimers, which crystallize into a hexatic
lattice and subsequently undergo a collective tilting instability. The resulting tilted dimers rotate and synchronize through hydrodynamic repulsion, which can be tuned by the Reynolds number. Upon synchronization, the polar director develops splay and bend deformations and nucleates topological defects with charges of $\pm1$. These defects induce long-wavelength concentration gradients and drive
crystal vortex dynamics spanning hundreds of particle diameters. Our results reveal a purely hydrodynamic route to synchronization and defect-mediated dynamics in
chiral active matter, without explicit
alignment rules or interparticle forces.
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All authors Zaiyi Shen, Leilei Wang, Shishuang Zhang, Chenlu Li, Kaili Xie, Xu Zheng, Juho S. Lintuvuori
Statistical Mechanics
Ergodic properties of occupation times in heterogeneous media
Vicenç Méndez and Rosa Flaquer-Galmés
We investigate the ergodic properties of Brownian motion in heterogeneous media through the statistics of occupation times. Using the Feynman-Kac formalism, we derive analytical expressions for the distributions, moments, and ergodicity breaking parameters of occupation times in two models with spatially varying
diffusion coefficient: a piecewise-constant profile and a power-law profile. In the piecewise model, the half occupation time and the occupation time within an interval follow asymmetric arcsine and half-Gaussian distributions, respectively, indicating non-ergodic behavior. For the power-law case, the corresponding distributions are the Lamperti and Mittag-Leffler. In both models, we identify a transition from non-ergodic to ergodic dynamics as the exponent vary. Numerical simulations fully corroborate the analytical results, demonstrating the effectiveness of the Feynman-Kac approach for quantifying ergodicity in heterogeneous
diffusion processes.
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Materials Science
Intrinsic structure of relaxor ferroelectrics from first principles
Xinyu Xu, Kehan Cai, Yubai Shi et al. (+2 more)
We develop FIRE-Swap, a first-principles framework for sampling intrinsic compositional structures in complex perovskites with machine-learning interatomic potentials (MLIPs). Using both dedicated and universal MLIPs, we study the relaxor lead magnesium niobate (PMN) and the solid solutions lead zirconate titanate (PZT) and lead strontium titanate (PST). Across MLIP models and exchange-correlation approximations, FIRE-Swap robustly predicts a rock-salt-like chemical order in PMN, which is absent in PZT and PST with the same mixing ratio, consistent with experiments. We further identify in PMN a distinct Nb-cluster morphology. Interconnected, non-coarsened polar nanoregions are found within Nb clusters, providing a mesoscale basis for understanding relaxor ferroelectricity.
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All authors Xinyu Xu, Kehan Cai, Yubai Shi, Peichen Zhong, Pinchen Xie
Strongly Correlated Electrons · Cross-listed from hep-th
Generalizing quantum dimensions: Symmetry-based classification of local pseudo-Hermitian systems and the corresponding domain walls
Yoshiki Fukusumi and Taishi Kawamoto
We study conformal field theories (CFTs) and their classifications from a modern perspective based on the abstract algebraic formalism of
symmetries or conserved charges, known as
symmetry topological field theories (SymTFTs). By studying the algebraic structure of the SymTFTs in detail, we found a natural generalization of the
quantum dimensions associated with (pseudo-)Hermitian systems and (non)-
unitary CFTs. These generalized data of SymTFTs provide classifications of massless and massive renormalization group flows, which will describe the
quantum phase transitions of the corresponding pseudo-Hermitian systems. Moreover, our discussions straightforwardly enable one to relate a general class of coset constructions or level-rank dualities to domain wall problems between topological
quantum field theories (or a series of corresponding
quantum phase transitions related to the
Higgs mechanism). Our work provides a systematic reduction and classification of algebraic data,
symmetries, for pseudo-Hermitian systems based on ideas from established mathematical fields, linear
algebra and ring theory.
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Soft Condensed Matter
Chiral active gyrator: Memory induced direction reversal of rotational motion
S Deion, F Adersh and M Sahoo
We theoretically explore the dynamics of a
chiral active Ornstein Uhlenbeck particle confined in a two-dimensional anisotropic harmonic trap. The particle is driven by chirality and is coupled to two orthogonal heat baths, potentially at two different temperatures. Using both analytical approach and numerical simulation, we explore the rotational dynamics of the particle in both viscous and viscoelastic environments. While the particle is suspended in a viscoelastic bath, characterized by a finite
memory time scale, we interestingly observe that even in the absence of a temperature gradient, the angular momentum changes its sign as a function of the
memory timescale, reflecting the direction reversal of rotational motion of the particle, and it is solely due to the interplay between
memory and chirality. This direction reversal is a distinct
memory-induced phenomenon and does not occur in the viscous limit. Moreover, increasing (or decreasing) the temperature gradient shifts the magnitude of the angular momentum further into the negative (or positive) direction, selecting a unique direction of rotation for the particle throughout the activity-
memory parameter space. However, in the viscous limit, the direction reversal of the rotational motion is still possible but occurs only across a neutral line in parameter space, along which the contributions from both chirality and thermal anisotropy to the net angular momentum exactly cancel. These results highlight a distinct mechanism for directional control in active systems, with
memory enabling reversal phenomena unique to viscoelastic media.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Maximizing the nondemolition nature of a quantum measurement via an adaptive readout protocol
Arjen Vaartjes, Rocky Yue Su, Laura A. O'Neill et al. (+15 more)
Quantum error correction (QEC) requires non-invasive measurements for fault tolerant
quantum computing. Deviations from ideal
quantum non-demolition (QND) measurements can disturb the encoded information. To address this challenge, we develop a readout protocol for a $D-$dimensional system that, after a single positive outcome, switches to probing only the $D{-}1$ remaining subspace. This adaptive switching strategy minimizes measurement-induced errors by relying on negative-result measurement results that do not perturb the
Hamiltonian. We apply the protocol on an 8-dimensional $^{123}{\rm Sb}$
nuclear qudit in silicon, and achieve an increase in the readout fidelity from $(98.93\pm0.07)\%$ to $(99.61\pm0.04)\%$, while reducing threefold the overall readout time. To highlight the broader relevance of measurement-induced errors, we study a 10-dimensional $^{73}{\rm Ge}$
nuclear spin read out through Pauli
spin blockade, revealing
nuclear spin flips arising from hyperfine and quadrupole interactions. These results unveil the effect of non-ideal QND readout across diverse platforms, and introduce an efficient readout protocol that can be implemented with minimal FPGA logic on existing hardware.
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All authors Arjen Vaartjes, Rocky Yue Su, Laura A. O'Neill, Paul Steinacker, Gauri Goenka, Mark R. van Blankenstein, Xi Yu, Benjamin Wilhelm, Alexander M. Jakob, Fay E. Hudson, Kohei M. Itoh, Chih Hwan Yang, Andrew S. Dzurak, David N. Jamieson, Martin Nurizzo, Danielle Holmes, Arne Laucht, Andrea Morello
Quantum Gases
Hopfions in the Lee-Huang-Yang superfluids
Liangwei Dong, Mingjing Fan, Boris A. Malomed et al. (+1 more)
It is known that, under appropriate conditions, mean-field interactions can be canceled in binary BEC, leading to the formation of the Lee-Huang-Yang (LHY) superfluid, in which the nonlinearity is solely represented by the quartic LHY term. In this work we systematically investigate the existence, stability and
evolution of hopfion states in this species of
quantum matter. They are characterized by two independent topological winding numbers: inner twist $s$ of the
vortex-ring core and overall vorticity $m$. The interplay between the LHY self-repulsion and a trapping harmonic-oscillator potential results in stability of the hopfions with $s = 1$ and $m$ ranging from $0$ to $4$. The hopfions exhibit distinct topological phase distributions along the vertical axis and the radial direction in the horizontal plane. Their effective radius and peak density increase with the chemical potential, along with expansion of the
vortex-ring core. Although the instability domain of the hopfion modes broadens with the increase of $m$, stable hopfions persist in a wide range of the chemical potential, up to $m=4$, at least, provided that the norm exceeds a certain threshold value. The predictions are experimentally accessible in currently used BEC setups.
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All authors Liangwei Dong, Mingjing Fan, Boris A. Malomed, Yaroslav V. Kartashov
Soft Condensed Matter
Sliding of cylindrical shell into a rigid hole
Yukiho Matsumoto, Keisuke Yoshida and Tomohiko G. Sano
Fitting two different materials is a versatile methodology in manufacturing complex structures. One of the canonical models for fitting is the snap-fit model, in which flexible materials and rigid structures are assembled by pushing their interlocking components together. The assembly via snap-fit is often accompanied by large deformations of flexible structures and abrupt force drops, highlighting the role of elasticity, geometry, and contact friction. Despite several model studies revealing fundamental mechanics for snap-fit, the current snap-fit design relies on prototyping and empirical rules. In this paper, we analyze a snap-fit model in which a naturally curved beam slips into a rigid hole. We construct an analytical model based on the theory of elastica with contact friction and demonstrate that its predictions are in excellent quantitative agreement with both simulations and experiments. We find three distinct sliding modes: Folding, Pinning, and Unfolding. The classification is systematically organized in a phase diagram based on the
geometric parameters of the shells and the hole. Our study complements existing approaches by providing a predictive framework for contact-based structures that involve friction, elasticity, and geometry, and sheds light on a unified understanding of the interactions between an elastic and a rigid body.
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