Mesoscale and Nanoscale Physics
Flow topology classification of limit cycles
Thomas Mutschler, Greta Villa and Oded Zilberberg
Recent topological tools offer a powerful way to classify how phases of nonlinear bosonic resonators are organized. Yet, they remain incomplete. In particular, self-sustained oscillations in the form of limit cycles act as robust organizing centers in phase space that are not captured by existing fixed-point-based approaches. In this work, we extend the flow
topology framework for nonlinear resonators to include limit cycles as fundamental topological elements. Using a graph-based construction, we show how periodic attractors impact the global connectivity of phase-space flows. We illustrate the approach with a minimal nonlinear Van der Pol resonator model, where limit cycles coexist with stationary points. Our results provide a unified topological description of stationary and time-periodic phases in nonlinear bosonic systems, with direct relevance to photonic, superconducting, and optomechanical platforms, and raise new questions on synchronization and the extension of flow
topology to the
quantum regime.
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Strongly Correlated Electrons · Cross-listed from physics.chem-ph
DoNOF 2.0: A modern Open-Source Electronic Structure Program for Natural Orbital Functionals
Juan Felipe Huan Lew-Yee, Ion Mitxelena, Jorge M. del Campo et al. (+1 more)
In this work, we present the second version of the Donostia Natural Orbital Functional Software, an open-source program for natural orbital functional calculations. The new release incorporates improved optimization
algorithms, capabilities for excited-state computations, support for ab initio molecular dynamics, and integration with the libcint library. DoNOF 2.0 also extends its property toolbox by enabling the evaluation of nonlinear optical responses, including static polarizabilities and higher-order hyperpolarizabilities via a finite-field Romberg-Richardson scheme. Program Summary [Title: DoNOF; Developer's repository link: http://github.com/DoNOF/; Program's Manual link: https://donof.readthedocs.io/; Licensing provisions: GPLv3; Programming
language: Fortran; additional implementations available in Python (PyNOF) and Julia (DoNOF.jl); Multinode capability: Support for distributed execution through a hybrid OpenMPI and OpenMP implementation]
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All authors Juan Felipe Huan Lew-Yee, Ion Mitxelena, Jorge M. del Campo, and Mario Piris
Strongly Correlated Electrons
Magnetic order and novel quantum criticality in the strongly interacting quasicrystals
Cong Zhang, Yin-Kai Yu, Shao-Hang Shi et al. (+1 more)
We present the sign-problem-free
quantum Monte Carlo study of the half-filled Hubbard model on two-dimensional quasicrystals, revealing how specific aperiodic geometries fundamentally dictate
quantum criticality. By comparing the Penrose and Thue-Morse quasicrystals, we demonstrate that the nature of the
magnetic phase transition is controlled by the electronic density of states (DOS): while the singular DOS of the Penrose tiling induces
magnetic order at infinitesimal interaction strengths, the Thue-Morse
lattice requires a finite critical interaction to drive the transition. Crucially, through a novel boundary construction strategy and rigorous finite-size scaling, we identify a
quantum critical point on the Thue-Morse quasicrystal with critical exponents ($\nu \approx 0.94$, $\beta \approx 0.72$ and $z\approx 1.51$) that deviate significantly from the conventional $(2+1)$D Heisenberg $O(3)$ class. These findings establish the existence of a novel universality class driven by the interplay between electronic correlations and aperiodic geometry, challenging standard paradigms of
magnetic criticality in two dimensions.
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All authors Cong Zhang, Yin-Kai Yu, Shao-Hang Shi, Zi-Xiang Li
Strongly Correlated Electrons
The classical-quantum disproportionation transition and magnetic ordering in RNiO$_3$ nickelates
A.S. Moskvin and Yu.D. Panov
The
insulator-quasi-metal (bad metal) transition observed in Jahn-Teller (JT) magnets orthonickelates RNiO$_3$ (R = rare earth, or yttrium Y) is considered a canonical example of the Mott transition, traditionally described in the framework of Hubbard's $U-t$ model. However, in reality, the insulating phase of nickelates is the result of charge disproportionation (CD) with the formation of a system of
spin-triplet ($S = 1$) electron [NiO$_6$]$^{10-}$ and spinless ($S = 0$) hole [NiO$_6$]$^{8-}$ centers, equivalent to a system of effective
spin-triplet composite
bosons moving in a nonmagnetic
lattice. The effective CD-phase
Hamiltonian takes into account local ($U$) and nonlocal ($V$) correlations, and the transfer of composite
bosons ($t_b$). Within the framework of the effective field approximation, we have shown the existence of two types of CD phases: the high-temperature classical paramagnetic CO-phase of charge ordering of electron and hole centers, and the low-temperature
magnetic quantum CDq phase with charge and
spin density transfer between electron and hole centers, with ”uncertain valence” [NiO$_{6}$]$^{(9\pm\delta)-}$ ($0 \le \delta \le 1$) and
spin density $(1 \pm \delta)/2$ NiO$_6$-centers. In the classical CO phase,
spin-triplet electron centers are surrounded by the nearest nonmagnetic hole centers, which ”turns off” the strong superexchange interaction of the nearest neighbors. The
magnetic ordering in the
quantum CDq phase is determined by a strong traditional superexchange and an unusual bosonic double exchange mechanism.
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Quantum Gases
Optically trapped Feshbach molecules of fermionic $^{161}$Dy and $^{40}$K: Role of light-induced and collisional losses
Alberto Canali, Chun-Kit Wong, Luc Absil et al. (+4 more)
We study the decay of a dense, ultracold sample of weakly bound DyK dimers stored in an optical dipole trap. Our bosonic dimers are composed of the fermionic isotopes $^{161}$Dy and $^{40}$K, which is of particular interest for experiments related to pairing and superfluidity in fermionic systems with mass imbalance. We have realized dipole traps with near-infrared
laser light in four different wavelength regions between 1050 and 2002 nm. We have identified trap-light-induced processes as the overall dominant source of losses, except for wavelengths around 2000 nm, where light-induced losses appeared to be much weaker. In a trap near 1550 nm, we found a plateau of minimal light-induced losses, and by carefully tuning the wavelength, we reached conditions where losses from inelastic collisions between the trapped dimers became observable. For very weakly bound dimers close to the center of a magnetically tuned Feshbach resonance, we demonstrate the Pauli suppression of collisional losses by about an order of magnitude.
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All authors Alberto Canali, Chun-Kit Wong, Luc Absil, Zhu-Xiong Ye, Marian Kreyer, Emil Kirilov, Rudolf Grimm
Soft Condensed Matter
Kovacs-like memory effect in strain stiffening collagen networks
Abhishek Ghadai and Sayantan Majumdar
Materials driven far from
equilibrium can encode
memories of past deformations through long-lived structural reorganisations. Such
memory effects-reflecting parameters such as deformation direction, magnitude, and duration have been widely explored in soft amorphous solids. Here, we report a Kovacs-like
memory effect manifested as a non-monotonic stress relaxation in vitro biopolymer networks formed by collagen, an essential component of the mammalian extracellular
matrix. Using shear rheology combined with in-situ optical imaging, we find that this
memory effect emerges exclusively in the nonlinear strain-stiffening regime, and persists over a much broader range of strain amplitudes than previously reported for other viscoelastic amorphous materials. Furthermore, we uncover a strong correlation between the
memory response and the development of negative normal stresses and associated strain fields, highlighting the unique nonequilibrium mechanics underlying
memory formation in biopolymer networks.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Multi-Photon Lasing Phenomena in Quantum Dot-Cavity QED
Lavakumar Addepalli
Multi-
photon lasing has been realized in systems with strong nonlinear interactions between emitters and cavity modes, where single-
photon processes are suppressed. Coherence between the internal states of a
quantum emitter, or among multiple emitters, plays a key role. Such continuous nonclassical sources of light can find applications in
quantum computation,
quantum sensing,
quantum metrology, and
quantum communication. This thesis explores the multi-
photon lasing phenomena in various
quantum dot-photonic
crystal cavity
quantum electrodynamic (QED) setups.
Exciton-
phonon interactions are inevitable in such systems and are incorporated using the polaron-transformed master equation. The Born-Markov approximation is employed to obtain the reduced density
matrix rate equation. Using
quantum laser theory, we derived the Scully-Lamb
laser rate equations and evaluated the single- and multi-
photon excess emission rates defined as the difference between emission and absorption rates into the cavity mode without mean-field approximations. We investigated cooperative two-
photon lasing, correlated emission lasing, hyperradiant lasing, non-degenerate two-mode two-
photon lasing, and continuous variable
entanglement in open
quantum systems with single or multiple
semiconductor quantum dots (two-level, three-level, and four-level) driven coherently/incoherently and coupled to single/ bimodal cavities.
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Materials Science
Impact of an electron Wigner crystal on exciton propagation
Daniel Erkensten, Alexey Chernikov and Ermin Malic
The strong Coulomb interaction in 2D materials facilitates the formation of tightly bound
excitons and charge-ordered phases of matter. A prominent example is the formation of a crystalline phase from free charges due to mutual Coulomb repulsion, known as the Wigner
crystal. While
exciton-electron interactions have been used as a sensor for Wigner crystallization, its impact on
exciton properties has been poorly understood so far. Here, we show that the weak potential induced by periodically ordered Wigner
crystal electrons has a major impact on
exciton propagation, albeit having only a minor influence on
exciton energy. The effect is tunable with carrier density determining the Wigner
crystal confinement and temperature via thermal occupation of higher subbands. Our work provides microscopic insights into the interplay between
excitons and charge-ordered states identifying key signatures in
exciton transport, and establishes a theoretical framework for understanding
exciton propagation in the presence of strong electronic correlations.
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Strongly Correlated Electrons
Generation of chirality and orbital magnetization by Stone-Wales-type lattice defects in the Kitaev spin liquid
Arnab Seth, Fay Borhani and Itamar Kimchi
In this work we extend our study of the effect of certain crystallographic defects on the
spin-1/2 Kitaev honeycomb
spin liquid (arXiv:2511.19409), focusing on its gapless phase and contrasting with the gapped phase. We identify a Stone-Wales (SW) local defect consisting of a 90$^\circ$ bond rotation that preserves Kitaev bond labels for edge-sharing octahedra and thereby enables exact solvability. These SW-type defects involve odd-sided plaquettes with $\pm \pi/2$ fluxes, but can be created locally. An isolated defect hosts a time-reversal pair of ground-state flux configurations with large net chirality. Certain excitations are also
chiral. The chirality manifests in Majorana local Chern marker and in scalar
spin chirality, producing electronic orbital magnetization. T-
matrix analysis and numerics at finite defect density $n_d$ show that defect chiralities generate a topological gap of $11 n_d$ protecting a Chern number $C=\pm 1$. Emergent
ferromagnetic long range Ising interactions $r^{-\gamma}$ with $2<\gamma < 3$ between defect chiralities lead to a finite temperature $T_c$ phase transition into the
chiral spin liquid. The $T_c$ is proportional to $n_d$ and diverges when $\gamma\rightarrow 2$. We also consider additional solvable
impurity potentials and find that $\gamma$ can be reduced to below $2.3$ and correspondingly enhance $T_c$. Our results offer applications to 2D Dirac cone systems with a finite density of fluctuating Ising
magnetic impurities and to identifying
spin liquids with
lattice defects.
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Mesoscale and Nanoscale Physics
Linear magnetoresistance of two-dimensional massless Dirac fermions in the quantum limit
Xiao-Bin Qiang, Han-Yi Xu, Ren-Jie Tong et al. (+4 more)
Linear magnetoresistance is a hallmark of 3D Weyl metals in the
quantum limit. Recently, a pronounced linear magnetoresistance has also been observed in 2D
graphene [Xin et al., Nature 616, 270 (2023)]. However, a comprehensive theoretical understanding remains elusive. By employing the self-consistent Born approximation, we derive the analytical expressions for the magnetoresistivity of 2D massless Dirac
fermions in the
quantum limit. Notably, our result recovers the minimum conductivity in the clean limit and reveals a linear dependence of resistivity on the
magnetic field for Gaussian
impurity potentials, in quantitative agreement with experiments. These findings shed light on the magnetoresistance behavior of 2D Dirac
fermions under ultra-high
magnetic fields.
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All authors Xiao-Bin Qiang, Han-Yi Xu, Ren-Jie Tong, Shuai Li, Zi-Xuan Gao, Peng-Lu Zhao, Hai-Zhou Lu
Statistical Mechanics · Cross-listed from math-ph
Gibbs state postulate from dynamical stability
Vjosa Blakaj, Matthias C. Caro, Anouar Kouraich et al. (+2 more)
Gibbs states play a central role in
quantum statistical mechanics as the standard description of thermal
equilibrium. Traditionally, their use is justified either by a heuristic, a posteriori
reasoning, or by derivations based on notions of typicality or passivity. In this work, we show that Gibbs states are completely characterized by assuming dynamical stability of the system itself and of the system in weak contact with an arbitrary environment. This builds on and strengthens a result by Frigerio, Gorini, and Verri (1986), who derived Gibbs states from dynamical stability using an additional assumption that they referred to as the "zeroth law of thermodynamics", as it concerns a nested dynamical stability of a triple of systems. We prove that this "zeroth law" is redundant and that an environment consisting solely of harmonic oscillators is sufficient to single out Gibbs states as the only dynamically stable states.
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All authors Vjosa Blakaj, Matthias C. Caro, Anouar Kouraich, Daniel Malz, Michael M. Wolf
Materials Science
Computational prediction of ferromagnetic AT6X6 kagome compounds
Shiya Chen, Zhen Zhang, Vladimir Antropov et al. (+1 more)
We present a systematic high-throughput density-functional-theory investigation of the structural and
magnetic stability of 312 substitutional compounds in the
magnetic kagome AT6X6 family. Our screening confirms the stability of many previously reported structures and predicts several additional stable candidates. Within collinear
spin configurations, we find that Fe-based systems predominantly adopt
antiferromagnetic ground states, whereas Mn-based analogues exhibit a more balanced distribution between
ferromagnetic and
antiferromagnetic order. For compounds exhibiting several nearly degenerate collinear configurations, we analyze the nature of their
magnetic ground states, assess the possible emergence of non-collinear order, and discuss the limitations and uncertainties inherent to standard density-functional approaches. Our electronic-structure analysis further reveals that newly predicted
ferromagnetic kagome systems display characteristic features of topological metals, with rich
magnetic configurations that can be tuned by chemical substitution. Overall, these
ferromagnetic kagome compounds constitute a broad and still largely unexplored materials platform for the emergence of exciting magneto-transport phenomena.
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All authors Shiya Chen, Zhen Zhang, Vladimir Antropov, Yang Sun
Soft Condensed Matter
Towards Animate Droplets: Active, Adaptive, and Autonomous
Joe Forth, Robert Malinowski and Giorgio Volpe
Droplets, sub-millilitre
liquid volumes with at least one interface, have traditionally served as compartments for storing, transporting, and delivering materials. Beyond familiar applications in food, coatings, and consumer goods, they find cutting-edge use in energy storage, sensing, and tissue engineering. The next frontier is their integration into animate matter, emerging materials defined by their levels of activity, adaptiveness, and autonomy. Easy to produce and dispense or print into complex structures, and with enormous chemical versatility, droplets are ideal building blocks for animate matter. In this Perspective, we outline a roadmap for advancing animacy in droplets and call for a more concerted effort to integrate novel mechanisms for motility, sensing, and decision-making into droplet design. Although research on active droplets spans more than a century, achieving true autonomy, where droplets process multiple stimuli and respond without external control, remains a central challenge. We hope to inspire interdisciplinary collaboration towards applications in consumer goods, microfluidics, adaptive optics, tissue engineering, and soft robotics.
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Disordered Systems and Neural Networks
Large Deviation Properties of Minimum Spanning Trees for Random Graphs
Mahdi Sarikhani and Alexander K. Hartmann
We study the large-deviation properties of minimum spanning trees for two ensembles of random graphs with $N$ nodes. First, we consider complete graphs. Second, we study Erdős-Rényi (ER) random graphs with edge probability $p=c/N$ conditioned to be connected. By using large-deviation Markov chain sampling, we are able to obtain the distribution $P(W)$ of the spanning-tree weight $W$ down to probability densities as small as $10^{-300}$. For the complete graph, we confirm analytical predictions with respect to the expectation value. For both ensembles, the large deviation principle is fulfilled. For the connected ER graphs, we observe a remarkable change of the distributions at the value of $c=1$, which is the percolation threshold for the original ER ensemble.
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Mesoscale and Nanoscale Physics
Gate-Tunable Giant Negative Magnetoresistance in Tellurene Driven by Quantum Geometry
Marcello B. Silva Neto, Chang Niu, Marcus V. O. Moutinho et al. (+5 more)
Negative magnetoresistance in conventional two-dimensional electron gases is a well-known phenomenon, but its origin in complex and topological materials, especially those endowed with
quantum geometry, remains largely elusive. Here, we report the discovery of a
giant negative magnetoresistance, reaching a remarkable $- 90\%$ of the resistance at zero
magnetic field, $R_0$, in $n$-type tellurene films. This record-breaking effect persists over a wide
magnetic field range (measured up to $35$ T) at cryogenic temperatures and is suppressed when the chemical potential shifts away from the Weyl node in the conduction band, strongly suggesting a
quantum geometric origin. We propose two novel mechanisms for this phenomenon: a
quantum geometric enhancement of
diffusion and a magnetoelectric
spin interaction that locks the
spin of a Weyl
fermion, in cyclotron motion under crossed electric $\boldsymbol{\cal E}$ and
magnetic ${\bf B}$ fields, to its guiding-center drift, $(\boldsymbol{\cal E}\times{\bf B})\cdot\sigma$. We show that the time integral of the velocity auto-correlations promoted by the
quantum metric between the
spin-split conduction bands enhance
diffusion, thereby reducing the resistance. This mechanism is experimentally confirmed by its unique magnetoelectric dependence, $\Delta R_{zz}(\boldsymbol{\cal E},{\bf B})/R_0=-\beta_{g}(\boldsymbol{\cal E}\times{\bf B})^2$, with $\beta_{g}$ determined by the
quantum metric. Our findings establish a new,
quantum geometric and non-Markovian
memory effect in magnetotransport, paving the way for controlling electronic transport in complex and topological matter.
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All authors Marcello B. Silva Neto, Chang Niu, Marcus V. O. Moutinho, Pierpaolo Fontana, Claudio Iacovelli, Victor Velasco, Caio Lewenkopf, Peide D. Ye
Superconductivity
Probing Pair Density Waves with Twisted Josephson Junctions
Jefferson Tang and Pavel A. Volkov
We show that twisted interfaces between
superconductors can serve as a phase-sensitive platform for the detection and characterization of pair density waves (PDW). In the presence of an in-plane
magnetic field, the critical Josephson current of a twisted PDW interface is maximal at a finite field value, determined by the twist angle and the PDW period – an explicit signature of the PDW. The results are robust to variations in junction geometry and can be adapted to certain cases with strong disorder or fluctuations. Their temperature dependence allows to distinguish pure PDW from byproducts of coexistence of superconductivity and charge- or
spin- density waves.
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Strongly Correlated Electrons
Successive magnetic transitions and multiferroicity in layered honeycomb BiCrTeO$_{6}$
Arkadeb Pal, P. H. Lee, J. Khatua et al. (+12 more)
Low-dimensional
magnetic systems based on honeycomb
lattices provide a promising platform for exploring exotic
quantum phenomena that emerge from the intricate interplay of competing
spin, orbital,
lattice, and dipolar degrees of freedom. Here, we present a comprehensive study of the layered honeycomb
lattice antiferromagnet BiCrTeO$_6$ using magnetization, specific heat,
muon spin–relaxation ($\mu$SR) spectroscopy, dielectric, pyrocurrent, and high-resolution synchrotron X-ray diffraction (SXRD) measurements. Our results reveal an array of intriguing and strongly correlated phenomena, including two successive
antiferromagnetic transitions at $T_{\rm N1}\approx16$ K and $T_{\rm N2}\approx11$ K, a pronounced magnetodielectric coupling effect, and ferroelectric order at $T_{\rm N2}$. Consequently, this compound emerges as a new
spin-driven multiferroic system. The SXRD analysis reveals a magnetoelastic-coupling-induced structural phase transition at $T_{\rm N2}$, characterized by a
symmetry lowering from P$\bar{3}$1c (163) to P31c (159), which likely triggers the onset of ferroelectricity. In addition to its low-temperature multiferroic behavior, the system exhibits dielectric relaxor characteristics at higher temperatures within the paramagnetic region ($T<50$ K), which is intrinsically linked to the antisite disorder of Cr and Te atoms.
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All authors Arkadeb Pal, P. H. Lee, J. Khatua, C. W. Wang, J. Gainza, A. Fitch, Thomas J. Hicken, H. Luetkens, Y.J. Hu, Ajay Tiwari, D. Chandrasekhar Kakarla, J. Y. Lin, K. Y. Choi, G. R. Blake, H. D. Yang
Statistical Mechanics · Cross-listed from quant-ph
Impact of Information on Quantum Heat Engines
Lindsay Bassman Oftelie and Michele Campisi
The emerging field of
quantum thermodynamics is beginning to reveal the intriguing role that information can play in
quantum thermal engines. Information enters as a resource when considering feedback-controlled thermal machines. While both a general theory of
quantum feedback control as well as specific examples of
quantum feedback-controlled engines have been presented, still lacking is a general framework for such machines. Here, we present a framework for a generic, two-stroke
quantum heat engine interacting with $N$ thermal baths and Maxwell's demon. The demon performs projective measurements on the engine working substance, the outcome of which is recorded in a classical
memory, embedded in its own thermal bath. To perform feedback control, the demon enacts
unitary operations on the working substance, conditioned on the recorded outcome. By considering the compound machine-
memory as a hybrid (classical-
quantum) standard thermal machine interacting with $N+1$ thermal baths, our framework puts the working substance and
memory on equal footing, thereby enabling a comprehensible resolution to Maxwell's paradox and elucidating the intricate manner in which information impacts the performance of
quantum engines. We illustrate the application of our framework with a two-
qubit engine. A remarkable observation is that more information does not necessarily result in better thermodynamic performance: sometimes knowing less is better.
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Superconductivity
Control of thin NbN film superconducting properties by ScN buffer layer
N.V. Porokhov, M.A. Dryazgov, A.R. Shevchenko et al. (+7 more)
This work investigates the effect of a scandium nitride buffer layer on the superconducting properties of niobium nitride thin films. The use of a ScN buffer layer significantly improves the characteristics of 29 nm thick NbN films: the critical temperature Tc increases from 9 K to 12.5 K, while the resistivity at 20 K decreases from 330 mkOhm*cm to 210 mkOhm*cm compared to films without a buffer layer. These enhancements are attributed to the better
lattice matching between NbN and ScN, which results in a higher quality
crystal lattice of the NbN film, as confirmed by transmission electron microscopy and X-ray diffraction data.
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All authors N.V. Porokhov, M.A. Dryazgov, A.R. Shevchenko, A.M. Mumlyakov, Z.S. Enbaev, Yu.V. Blinova, D.I. Devyaterikov, Yu.P. Korneeva, A.A. Korneev, M. A. Tarkhov
Materials Science
Developing a valence force field model for wurtzite semiconductors by exploiting similarities with [111]-oriented zinc blende systems: The case of wurtzite boron nitride, III-N materials and (B,In,Ga)N alloys
Aisling Power, Cara-Lena Nies and Stefan Schulz
Controlling the
crystal phase and
lattice mismatch of
semiconductors offers a powerful route to engineer electronic and optical properties of
heterostructures. As a consequence,
semiconductors in the wurtzite phase are increasingly sought after, superseding the thermodynamically favored cubic zinc blende phase. Empirical atomistic modeling, required for large scale simulations of
heterostructures and their properties, relies heavily on valence force field (VFF) methods to find the
equilibrium atomic positions in an
alloy. For zinc blende
crystals, VFF models are well-established. In the case of wurtzite, such parameters are frequently adopted without rigorous analysis, despite subtle but consequential differences from the zinc blende structure. Such an approach can compromise accuracy in describing material properties, since the structural differences between zinc blende and wurtzite directly influence electronic and optical characteristics. Based on the analytical VFF model by Tanner et al., and using structural similarities between wurtzite and [111]-oriented zinc blende, we construct a wurtzite VFF without introducing additional parameters. Our framework relies on analytic expressions and minimization routines to project zinc blende models onto wurtzite systems. Beyond elastic tensors, we train the model to reproduce bond length asymmetries and band gaps by using output of the VFF model in density functional theory calculations. Applied to wurtzite III-N compounds and BN, the model accurately reproduces targeted observables but also properties it has not been trained on, including the internal parameter u. We further validate the model on highly mismatched
alloys such as (B,Ga)N and (B,In,Ga)N, exhibiting good agreement between VFF and density functional theory results when using identical supercells in these calculations.
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Mesoscale and Nanoscale Physics
Transport of Dirac magnons driven by gauge fields
Luis Fernández, Ka Shen, Leandro O. Nascimento et al. (+3 more)
We present a unified
quantum field theory for Dirac
magnons coupled to emergent gauge fields. At zero temperature, any space- and time-dependent gauge perturbation drives
magnons out of
equilibrium, generating
spin currents and
magnon accumulation without conventional thermal or chemical potential gradients. For a honeycomb ferromagnet, we derive closed-form expressions for the induced density and current. In the DC limit, the transverse
spin conductivity quantizes to $\sigma^{xy}=\alpha^2\text{sgn}(m)\hbar/4\pi$, a magnonic analog of the
quantum Hall effect, where $m$ is the topological
magnon mass and $\alpha$ a dimensionless coupling constant. In the AC regime, the conductivity exhibits a sharp resonance when the drive frequency matches the topological gap $\Delta$, signaling interband transitions. Our work establishes gauge fields as a versatile tool for controlling
magnon transport and reveals topologically protected quantized responses.
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All authors Luis Fernández, Ka Shen, Leandro O. Nascimento, Van Sérgio Alves, Roberto E. Troncoso, Nicolas Vidal-Silva
Soft Condensed Matter
Diffusiophoretic migration of colloidal particles in sucrose gradients
Antoine Monier, Brielle Byerley, Julien Renaudeau et al. (+3 more)
Diffusiophoresis (DP) refers to the migration of particles driven by a solute concentration gradient in a
liquid. Observations in the case of molecular neutral solutes are rather scarce, due to the low drift velocities in dilute solutions, and the difficulty in distinguishing DP from other phenomena in concentrated solutions. We investigated experimentally DP of dispersed colloids driven by concentration gradients of sucrose in water at relatively high concentrations, $C \simeq 1$ mol L$^{-1}$. More precisely, we designed a microfluidic chip to impose a time-dependent sucrose gradient in dead-end microchannels with minimized parasitic flows. Significant migration of the particles toward the regions of low sucrose concentration has been observed, with velocities up to a few $\mu$m s$^{-1}$. Particle tracking and Raman confocal spectroscopy were used to measure individual trajectories and the unsteady sucrose concentration profile respectively. The latter is correctly described by a
diffusion equation, but with an interdiffusion coefficient that significantly depends on $C$ in the range of concentrations investigated. We then showed that a model of DP based on a steric exclusion of sucrose molecules from the particle surface with an exclusion length $R_i = 5 \pm 0.9$ angstrom (close to the characteristic size of the sucrose molecule), accounts for the observed trajectories. Possible sources for the observed scattering of our experimental data are finally discussed: Brownian motion and advection of the particles by bulk flows driven by diffusioosmosis at the channel walls and buoyancy.
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All authors Antoine Monier, Brielle Byerley, Julien Renaudeau, H. Daniel Ou-Yang, Pierre Lidon, Jean-Baptiste Salmon
Mesoscale and Nanoscale Physics
Theoretical investigation of two-dimensional semiconductor nanoribbons and nanoparticles for tailored light–matter interactions
Christian Nicolaisen Hansen, Line Jelver and Christos Tserkezis
We explore theoretically the optical response of two-dimensional (2D) materials patterned at the nanoscale into either arrays of ribbons along a planar surface or spherical particles.
Fourier-Floquet decomposition of the electromagnetic fields is used in order to obtain the reflectance, transmittance and absorbance of the nanoribbon array. The spherical particles are treated with Mie theory, with the boundary conditions modified to accommodate a surface conductivity at the interface. We consider the excitonic response of hexagonal boron nitride in the ultraviolet, and of the transition-metal dichalcogenide WS2 in the visible. Unlike what is expected from
graphene, where plasmons have proven very sensitive to geometry, the excitonic response of nanoribbon arrays is found to show weak tunability with the array parameters. To enhance tunability with the geometry of the system, or via hybridization with the substrate, nanospheres with a 2D
semiconductor coating are demonstrated to provide a superior platform. Overall, we find that the localized nature of
excitons in 2D
semiconductors largely limits tunability with geometry, but their hybridization with other optical modes in the nanopatterning setup still holds promise for controllable light–matter interactions.
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Statistical Mechanics
Deriving the Eigenstate Thermalization Hypothesis from Eigenstate Typicality and Kinematic Principles
Yucheng Wang
The eigenstate thermalization hypothesis (ETH) provides a powerful framework for understanding thermalization in isolated
quantum many-body systems, yet a complete and conceptually transparent derivation has remained elusive. In this work, we derive the structure of ETH from a minimal dynamical principle, which we term the eigenstate typicality principle (ETP), together with general kinematic ingredients arising from
entropy maximization,
Hilbert-space geometry, and locality. ETP asserts that in
quantum-chaotic systems, energy eigenstates are statistically indistinguishable, with respect to local measurements, from states drawn from the Haar measure on a narrow microcanonical shell. Within this framework, diagonal ETH arises from concentration of measure, provided that eigenstate typicality holds. The structure of off-diagonal
matrix elements is then fixed by entropic scaling and the finite-time dynamical correlations of local observables, with ETP serving as the dynamical bridge to energy eigenstates, without invoking random-
matrix assumptions. Our results establish ETH as a consequence of
entropy,
Hilbert-space geometry, and chaos-induced eigenstate typicality, and clarify its regime of validity across generic
quantum-chaotic many-body systems, thereby deepening our understanding of
quantum thermalization and the emergence of statistical mechanics from
unitary many-body dynamics.
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Soft Condensed Matter
Scaling Laws and Universal Features of Tethered Polymer Distributions in Confined Geometries
Bibhatsu Kuiri, Rittwick Mondal, Dipankar Biswas et al. (+1 more)
We develop a unified scaling framework for the end-position distributions of tethered
polymers confined in finite cylindrical geometries. Two observables are analysed: the longitudinal distribution P(x), along the confinement axis, and the transverse distribution P(y), perpendicular to the confinement axis. Using exact
Fourier-sine and image-method representations with adaptive numerical schemes, we construct and test six scaling strategies for P(x) and five for P(y), encompassing
geometric similarity, tether-position sweeps, confinement-strength crossovers, persistence-length effects, boundary-layer scaling near absorbing walls, and tether-centered coil scaling. Quantitative collapse diagnostics such as RMS residuals on common support, modal-energy fractions, and survival probabilities are combined with limiting-regime analysis and direct numerical evaluation to distinguish genuine universality from visually misleading overlap. From these tests we obtain a kappa-based confinement diagram and a two-parameter (kappa, a/L) regime map that link classical theories such as Flory/de Gennes blobs, Odijk deflection segments, and wormlike-chain behaviour within a single spectral picture. Gaussian, multimode, and eigenmode-dominated regimes are identified by explicit thresholds in modal composition and collapse error, providing operational criteria for when Gaussian or single-mode descriptions are valid and when full multimode structure is required. The resulting framework provides a compact, reproducible toolkit for analysing confined-
polymer statistics, with applications to simulations and experiments on DNA, chromatin, and other biopolymers where confinement, stiffness, and tethering jointly control spatial organization.
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All authors Bibhatsu Kuiri, Rittwick Mondal, Dipankar Biswas, Soumyajyoti Kabi
Mesoscale and Nanoscale Physics
Chirality Imprinting and Spin-texture Tunability in Conformally Coated 3D Magnetic Nanostructured Metamaterials
Alexander Roberts, Huixin Guo, Joseph Askey et al. (+4 more)
Three-dimensional (3D)
magnetic nanostructures offer unprecedented opportunities for engineering emergent
spin textures, but controlling their configuration remains a central challenge. Here we show that conformally coated Ni Nanotubes arranged in a woodpile geometry with
lattice spacings ranging from 800 to 1200 nm, realised by two-
photon lithography and atomic layer deposition, exhibit a geometry-tuneable balance between
chiral and axial states.
Magnetic force microscopy on the top layer of the 3D woodpile reveals that few-layer systems exhibit a
chiral contrast whilst increasing the number of stacked layers drives a transition to an axial configuration with the change in state populations depending strongly on
lattice spacing. Micromagnetic simulations demonstrate that chirality is not intrinsic to isolated tubes but is imprinted by
spin textures formed in the substrate sheet film, which couple into the 3D network. As the sheet-film influence diminishes with increasing layer number, dipolar interactions dominate and stabilise the axial state. This two-stage mechanism of chirality imprinting followed by increasingly dominant dipolar interactions, provides clear control parameters for tailoring
spin-texture populations. Our results establish conformally coated woodpiles as a reconfigurable 3D
ferromagnetic metamaterial platform that can be exploited for data storage, magnonics, and neuromorphic computing.
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All authors Alexander Roberts, Huixin Guo, Joseph Askey, Vani Lanka, Arjen van den Berg, Dirk Grundler, Sam Ladak
Statistical Mechanics
Spectral Entropy via Random Spanning Forests
Carlo Nicolini
We establish an exact analytic relation between random spanning forests and the heat-kernel partition function. This identity enables estimation of partition functions, energies, and the Von Neumann
entropy by Wilson sampling of forests, avoiding costly
Laplacian eigendecompositions. We validate inverse-Laplace reconstructions stabilized by a Stieltjes spectral-density regularization on synthetic networks. The approach is scalable and yields local node and edge thermodynamic descriptors.
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Materials Science
Heterostructure Design in Two-Dimensional Perovskites by Sequential Recrystallization
Mehrdad Faraji, Alexander Schleusener, Sirous Khabbaz Abkenar et al. (+9 more)
Low-dimensional metal halide perovskites provide exciting opportunities to fabricate new
semiconductor materials.
Semiconductor technology relies on electronic heterojunctions, and cost-efficient and flexible approaches to realize functional
heterostructures are of fundamental importance. Lateral
heterostructures define the energy landscape in the plane of the semiconducting
lattice in such 2D materials, representing an ideal platform to tailor energy barriers and to control charge carrier flow. Here, we demonstrate a versatile one-pot synthesis to fabricate a large variety of 2D perovskite
heterostructures based on different halides and/or metal cations. Exploiting sequential crystallization of different 2D perovskites, and playing with the composition and injection events of the materials, enables the design of diverse
heterostructure architectures including multiple heterojunctions. We obtain crystalline quality of the heterojunctions, multicolor emission, and optical coupling between the different
heterostructure regions. We foresee that the design freedom of our method will stimulate the development of novel optoelectronic devices where electronic band engineering is crucial.
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All authors Mehrdad Faraji, Alexander Schleusener, Sirous Khabbaz Abkenar, Andrea Griesi, Mattia Lizzano, Sudhir Kumar Saini, Aswin V. Asaithambi, Liberato Manna, Matteo Lorenzoni, Mirko Prato, Giorgio Divitini, Roman Krahne
Quantum Gases
Observation of a supersolid stripe state in two-dimensional dipolar gases
Yifei He, Haoting Zhen, Mithilesh K. Parit et al. (+5 more)
Fluctuations typically destroy long-range order in two-dimensional (2D) systems, posing a fundamental challenge to the existence of exotic states like supersolids, which paradoxically combine solid-like structure with frictionless superfluid flow. While long-predicted, the definitive observation of a 2D supersolid has remained an outstanding experimental goal. Here, we report the observation of a supersolid stripe phase in a strongly dipolar
quantum gas of erbium atoms confined to 2D. We directly image the periodic density modulation, confirming its global phase coherence through matter-wave interference and demonstrating its phase
rigidity relevant to the low-energy Goldstone mode, consistent with numerical calculations. Through collective excitation measurements, we demonstrate the hydrodynamic behavior of the supersolid. This work highlights a novel mechanism for supersolid formation in low dimensions, and opens the door for future research on the intricate interplay between temperature, supersolidity, and dimensionality.
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All authors Yifei He, Haoting Zhen, Mithilesh K. Parit, Mingchen Huang, Nicolò Defenu, Jordi Boronat, Juan Sánchez-Baena, Gyu-Boong Jo
Mesoscale and Nanoscale Physics
Chiral-helical junctions in screened graphene
Bilal Kousar, Selma Franca, David Perconte et al. (+14 more)
Reproducibility and quantization in
quantum spin Hall platforms is a persisting challenge, limiting their use in hybrid realizations of topological superconductivity. We report robust and reproducible quantized transport in a
graphene quantum Hall topological
insulator, stabilized at low
magnetic fields by screening long-range Coulomb interactions with a metallic Bi$_2$Se$_3$ back gate. Beyond quantized resistance plateaus, we demonstrate mode-resolved control via gate-defined
chiral-helical junctions that selectively transmit or backscatter a single helical channel, a capability inaccessible in time-reversal symmetric
quantum spin Hall systems. Targeted experiments and simulations identify contact-induced doping, effectively creating unintended
chiral-helical interfaces, as a generic mechanism for quantization breakdown, which is mitigated by large area contacts that enhance edge-channel equilibration. Our findings establish metal screened
graphene as a gate-tunable, interaction-driven helical system with quantized transport, spatially separable helical channels, and compatibility with superconducting proximity for topological devices.
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All authors Bilal Kousar, Selma Franca, David Perconte, Anton Khvalyuk, Wenmin Yang, Hadrien Vignaud, Frédéric Gay, Kenji Watanabe, Takashi Taniguchi, Clemens B. Winkelmann, Yangtao Zhou, Zheng Vitto Han, Alexandre Assouline, Jens H. Bardarson, Adolfo G. Grushin, Hermann Sellier, Benjamin Sacépé