Statistical Mechanics
Scaling at Chiral Clock Criticality via Entanglement Renormalization
Shiyong Guo and Brian Swingle
We employ the Multiscale
Entanglement Renormalization Ansatz (MERA) tensor network to investigate a critical line of continuous
quantum phase transitions of the $\mathbb{Z}_3$
chiral clock model. This critical line is believed to be described by a slow renormalization group flow from the 3-state Potts fixed point to another fixed point that features anisotropic scaling of space and time. We use the variational principle to construct a MERA representation of the model's ground state, from which we obtain the ground state energy and the set of scaling operators and their scaling dimensions. These scaling dimensions determine the critical exponents of the model, and we study these critical exponents and other scaling data as a function of the model's
chiral parameter. We find a set of effective scaling data that smoothly varies starting from the Potts data as the
chiral parameter is increased. Within the context of our approach, we discuss how this result may nevertheless be consistent with the two fixed point hypothesis provided the renormalization group flow is sufficiently slow. Our findings demonstrate MERA's effectiveness in capturing the complex low-energy physics of the
chiral clock model and in extracting field theory data for an anisotropic continuum theory.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Measurement and feedback-driven adaptive dynamics in the classical and quantum kicked top
Mahaveer Prasad, Ahana Chakraborty, Thomas Iadecola et al. (+4 more)
In classical dynamical systems,
stochastic feedback can stabilize otherwise unstable periodic orbits, giving rise to distinct controlled and uncontrolled phases as the rate of control application is varied. In this work, we apply these control protocols in classical, semiclassical, and
quantum regimes to the kicked top, a paradigmatic model of
quantum chaos. The
quantum kicked top, modeled as the dynamics of a
spin-S object, naturally interpolates between these regimes with the
spin size S acting as an effective Planck constant. We show that the dynamics of the kicked top in classical, semiclassical, and fully
quantum limits can all be controlled using
stochastic feedback protocols. Comparing the full
quantum dynamics to a truncated Wigner approximation that captures
quantum noise but neglects interference beyond the Ehrenfest time, we find that low-moment observables are largely accounted for semiclassically, while higher moments retain a discrepancy that peaks at the control transition, consistent with contributions from interference and possibly nonlinearities in rare trajectories that explore the compact phase space. We also find rapid purification in the numerics studied for all rates of control considered, suggesting that control quenches the top's ability to encode a
qubit of
quantum information even in the uncontrolled phase.
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All authors Mahaveer Prasad, Ahana Chakraborty, Thomas Iadecola, Manas Kulkarni, J. H. Pixley, Sriram Ganeshan, Justin H. Wilson
Strongly Correlated Electrons
Melting temperature shifts from quantum fluctuations in generalized Wigner crystals
Aman Kumar, Sogoud Sherif, Veit Elser et al. (+1 more)
It is generally believed that
quantum fluctuations collaborate with thermal fluctuations, effectively reducing transition temperatures (e.g. for melting of charge order). We show that this is not always the case and that the interplay between
quantum and thermal fluctuations can be competitive. We find excellent motivation for addressing this thanks to the discovery of correlated insulating "generalized Wigner
crystal" (GWC) states in hetero-
bilayer transition metal dichalcogenide (WS$_2$/WSe$_2$) moiré systems [Y. Xu, et al., Nature 587, 214-218 (2020)]. We account for the impact of
quantum effects on the melting temperature of GWCs, carrying out finite temperature Lanczos calculations on an extended Hubbard model on the triangular
lattice (both with a double-gate screened potential, and the nearest neighbor model) for multiple electron densities. We show that
quantum effects capture the shift relative to the classical estimates, which in some cases are more than 50 percent off from the experimental values. Then building on these numerical findings, we provide a qualitative picture that clarifies that while
quantum melting of GWC (by increasing the bandwidth) naturally softens the ground state order parameter, it does not always decrease the melting temperature; conversely it can increase it. To do so we employ a finite temperature perturbation theory, treating the kinetic energy perturbatively on top of a classical Wigner
crystal. Our predictions should be observable in future experiments where the bandwidth can be tuned.
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All authors Aman Kumar, Sogoud Sherif, Veit Elser, Hitesh J. Changlani
Statistical Mechanics · Cross-listed from hep-th
Crosscap Defects
Nadav Drukker, Shota Komatsu and Anders Wallberg
We introduce a novel class of defects, termed crosscap defects, in conformal field theory (CFT) in general dimensions. These arise from quotienting the spacetime by a $Z_2$
automorphism, and provide higher-codimension generalisations of CFT on real projective space ($RP^{d}$). Crosscap defects extend along a $p$-dimensional fixed locus of the $Z_2$ action and preserve an $SO(p+1,1)\times PO(d-p)$ subgroup of the conformal group. The two-point functions of operators in this setup exhibit three operator product expansion channels: bulk, image, and defect. These lead to several crosscap crossing equations, which we present. We analyse conformal block decompositions and show that the blocks are identical to defect CFT blocks up to a redefinition of cross ratios. As concrete examples, we study crosscap defects in the $O(N)$ model at the Gaussian and Wilson–Fisher fixed points in the $\varepsilon$-expansion. We compute explicitly the associated CFT data as a function of $p$ and find that, unlike standard defects, displacement and tilt operators are absent for generic $p$. They provide examples of defect conformal
manifolds without exactly marginal operators.
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Statistical Mechanics · Cross-listed from quant-ph
Bootstrapping Open Quantum Many-body Systems with Absorbing Phase Transitions
Minjae Cho, Colin Oscar Nancarrow, Petar Tadić et al. (+1 more)
We demonstrate that combining the positivity of density
matrices with steady-state conditions yields a systematic bootstrap method for studying open
quantum many-body systems governed by Lindblad master equations on infinite
lattices, which exhibit absorbing phase transitions. As a concrete example, we apply this method to the
quantum contact process with an absorbing state. We obtain bootstrap bounds on steady-state expectation values, the critical coupling, certain ratios of expectation values in the nontrivial steady state in the supercritical phase, and the Liouvillian spectral gap in the subcritical phase.
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All authors Minjae Cho, Colin Oscar Nancarrow, Petar Tadić, Yuan Xin
Materials Science
Organosilane-functionalized hydrothermal-derived coatings on titanium alloys for hydrophobization and corrosion protection
S. Rahimipour, B. Rafiei and E. Salahinejad
This work focuses on the structure, wettability and corrosion behaviors of Ti-6Al-4V
alloy after roughening treatments in different concentrations of NaOH aqueous solutions followed by low surface energy hexadecyltrimethoxysilane (HDTMS) coating. In this regard, scanning electron microscopy, contact angle measurements, potentiodynamic polarization and electrochemical impedance spectroscopy were used to characterize the samples. In contrast to hydrophilicity caused by the hydrothermal alkaline treatments, the subsequent HDTMS coating donated considerable hydrophobicity. Typically, the highest sessile water contact angle (about 147 deg) was obtained for the sample treated in 3 molar NaOH solution followed by the HDTMS coating. In addition, the alkaline treatment reduced the corrosion resistance of the surface in a NaCl aqueous solution; however, the HDTMS hydrophobization process improved it significantly. It is eventually concluded that the coupled use of alkaline treatment and HDTMS functionalization can be further considered for moisture-exposed applications of Ti-based
alloys.
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Disordered Systems and Neural Networks · Cross-listed from cs.LG
Ultrametric OGP - parametric RDT symmetric binary perceptron connection
Mihailo Stojnic
In [97,99,100], an fl-RDT framework is introduced to characterize statistical computational gaps (SCGs). Studying symmetric binary perceptrons (SBPs), [100] obtained an algorithmic threshold estimate $\alpha_a\approx \alpha_c^{(7)}\approx 1.6093$ at the 7th lifting level (for $\kappa=1$ margin), closely approaching $1.58$ local
entropy (LE) prediction [18]. In this paper, we further connect parametric RDT to overlap gap properties (OGPs), another key
geometric feature of the solution space. Specifically, for any positive integer $s$, we consider $s$-level ultrametric OGPs ($ult_s$-OGPs) and rigorously upper-bound the associated constraint densities $\alpha_{ult_s}$. To achieve this, we develop an analytical union-bounding program consisting of combinatorial and probabilistic components. By casting the combinatorial part as a convex problem and the probabilistic part as a nested integration, we conduct numerical evaluations and obtain that the tightest bounds at the first two levels, $\bar{\alpha}_{ult_1} \approx 1.6578$ and $\bar{\alpha}_{ult_2} \approx 1.6219$, closely approach the 3rd and 4th lifting level parametric RDT estimates, $\alpha_c^{(3)} \approx 1.6576$ and $\alpha_c^{(4)} \approx 1.6218$. We also observe excellent agreement across other key parameters, including overlap values and the relative sizes of ultrametric clusters. Based on these observations, we propose several
conjectures linking $ult$-OGP and parametric RDT. Specifically, we
conjecture that algorithmic threshold $\alpha_a=\lim_{s\rightarrow\infty} \alpha_{ult_s} = \lim_{s\rightarrow\infty} \bar{\alpha}{ult_s} = \lim_{r\rightarrow\infty} \alpha_{c}^{(r)}$, and $\alpha_{ult_s} \leq \alpha_{c}^{(s+2)}$ (with possible equality for some (maybe even all) $s$). Finally, we discuss the potential existence of a full isomorphism connecting all key parameters of $ult$-OGP and parametric RDT.
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Statistical Mechanics · Cross-listed from math-ph
The bosonic Hubbard model on a three dimensional flat band lattice
Leon Haag-Fank and Andreas Mielke
The lowest eigenstates of the hopping
matrix on the line graph of a cubic
lattice with periodic boundary conditions are highly degenerate, they form a lowest flat band. Further, these states are localized. If one considers a repulsive bosonic Hubbard model on this
lattice it is possible to construct exact multi-particle ground states simply by putting particles in the localized single particle ground states such that they avoid each other. This can be done up to a certain critical particle number $N_c$. We prove that at this particle number the ground state
entropy is subextensive $\propto N_c^{2/3}$. For lower densities the
entropy is extensive. We further show that the problem is related to the number of 4-cycle decompositions of the cubic
lattice with periodic boundary conditions.
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Statistical Mechanics · Cross-listed from physics.soc-ph
Cycle holonomy captures higher-order compatibility constraints in remote synchronization
Lluís Torres-Hugas, Jordi Duch, Sergio Gómez et al. (+1 more)
Higher-order interactions have typically been modeled using hypergraphs or simplicial complexes, where interactions explicitly involve more than two nodes. Here we demonstrate that effective higher-order dynamical constraints emerge naturally on ordinary graphs, provided the interaction carries nontrivial topological structure. We study a gauge-coupled phase model with edge phase lags whose accumulation around closed loops produces gauge-invariant mismatches. We show that the associated twisted
Laplacian admits a zero mode if and only if all cycle holonomies vanish. Consequently, global compatibility is obstructed not by local pairwise mismatches, but by intrinsic topological frustration on cycles. We then connect this framework to the symmetric Sakaguchi–Kuramoto model, whose local coupling law differs from the gauge-coupled model but whose node phases impose cycle closure on physical phase differences. For cactus graphs, path mismatches induced by the symmetric lag can be represented through associated cycle holonomies, providing a static spectral encoding of their global residual incompatibility. Our results establish a spectral framework linking frustration to cycle-level constraints and identify cycle holonomy as a local-to-global diagnostic of path incompatibility in synchronization dynamics.
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All authors Lluís Torres-Hugas, Jordi Duch, Sergio Gómez, Alex Arenas
Materials Science
Intrinsic $i$-wave altermagnetism in 2D graphene superlattices
Cuiju Yu and Jose L. Lado
Altermagnets feature unconventional magnetism due to their momentum-dependent
spin splitting purely driven by
magnetic order, for which a variety of transition-metal-based $d$-wave altermagnets have been proposed. However, carbon-based altermagnets remain largely unexplored, even though magnetism of
graphene nanostructures has been widely demonstrated. Here, through a comprehensive
symmetry analysis, we establish a
symmetry-guided design principle for realizing higher-order $i$-wave altermagnetism in
graphene antidot superlattices and demonstrate its emergence in both monolayer and
bilayer graphene, particularly in the Bernal-stacked
bilayer. By combining atomistic tight binding models and first principles methods, we show the appearance of an interaction-induced $i$-wave altermagnetic splitting, originating from the intrinsic
magnetic instability of 2D
graphene antidot superlattices. Our work establishes a strategy to engineer $i$-wave altermagnetism in a
graphene platform, extending the materials landscape beyond conventional $d$-wave altermagnets and putting forward a carbon-based platform for higher-order altermagnetic spintronics.
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Materials Science
Atomic-scale origin of charge density wave-driven metal-semiconductor transition in an incommensurately modulated metal-organic framework
Ling Zhang, Zeyue Zhang, Liu He et al. (+18 more)
The intrinsic incommensurate charge density wave in metal-organic frameworks has remained elusive due to the lack of direct evidence linking atomic-scale structural modulation to macroscopic electronic properties. Using high-quality Pr3HHTP2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) single
crystals as a model system, we precisely resolve, for the first time, the incommensurately modulated structure of a conductive metal-organic framework at 100 K (modulation vector q = 0.39143(12) c*) via temperature-dependent single-
crystal X-ray diffraction. The subsequent observation of a reversible metal-
semiconductor transition around 350 K, which perfectly synchronizes with the disappearance of the structural modulation, provides convincing evidence for the electronic origin of the
lattice distortion. Guest water molecules stabilize the modulated phase by synergistically regulating the relative rotation of the linkers and the interlayer spacing, thereby optimizing the inter-linker interactions. This work establishes a concrete experimental criterion for one-dimensional charge density wave in metal-organic frameworks and provides an ideal platform for probing coupled electronic-
lattice modulations.
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All authors Ling Zhang, Zeyue Zhang, Liu He, Bin Jiang, Yingchao Wang, Jiaxiang Zhang, Huimin Qi, Chao Zhang, Jinkun Guo, Hao Chen, Yunlong Fan, Yanran Shen, Hongli Jia, Guobao Li, Yu-Qing Zheng, Julius J. Oppenheim, Tianyang Chen, Jian Wang, Lei Sun, Junliang Sun, Jin-Hu Dou
Materials Science
Electronic structure and oxidation states in high-pressure synthesized isostructural CeCN$_5$ and TbCN$_5$
Amanda Ehn, Florian Trybel, Talha Bin Masood et al. (+2 more)
Understanding the behavior of 4$f$ electrons in materials containing rare earth elements is one of the fundamental questions within condensed matter physics. In this work the electronic properties of isostructural CeCN$_5$ and TbCN$_5$, both recently synthesized at extreme pressure, are investigated using Density Functional Theory (DFT) calculations. We include the on-site Coulomb repulsion between localized 4$f$ states within the static DFT+U framework; the DFT+U results are cross-checked with DFT+dynamical mean-field theory (DMFT) calculations within the quasi-atomic (Hubbard-I) approximation. Despite CeCN$_5$ and TbCN$_5$ being isostructural compounds Ce and Tb show different oxidation states, 4+ and 3+ respectively. This leads to distinctly different electronic properties: the former compound is an
insulator, while the latter is a metal. An extra electron which is donated by Ce to the polymeric C-N network is distributed across the network. This leads to a modification of the bond length in CeCN$_5$ compared to TbCN$_5$. Still, the polymeric C-N networks can accommodate the different oxidation states in isostructural lanthanide-carbon-nitrogen (LnCN) compounds. Our results underline that LnCN compounds under high pressure offer a unique platform for probing the interplay between 4$f$-electron behavior and structural complexity.
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All authors Amanda Ehn, Florian Trybel, Talha Bin Masood, Leonid V. Pourovskii, Igor A. Abrikosov
Materials Science
Lattice thermal transport from phonon spectra beyond perturbation theory
Zezhu Zeng, Michele Simoncelli and David E. Manolopoulos
We develop a molecular dynamics framework to compute the mode-resolved
phonon spectral density from classical correlations of an annihilation-like
phonon variable. For harmonic oscillators, classical molecular dynamics exactly reproduces the corresponding
quantum Kubo-transformed correlator, providing the basis for extension to anharmonic systems. Using PbTe as a
benchmark and Cs$_3$Bi$_2$I$_6$Cl$_3$ as a strongly anharmonic test case, we show that the method captures both quasiparticle and non-Lorentzian spectra beyond perturbative quasiparticle theory, while yielding thermal conductivity in good agreement with experiment. This framework provides a classical molecular dynamics route to mode-resolved
phonon spectral densities for spectral Wigner heat transport in strongly anharmonic solids above their Debye temperatures.
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Mesoscale and Nanoscale Physics
Supermoiré domain-resolved effective Hamiltonians and valley topology in helical multilayer graphene
Kyungjin Shin, Nicolas Leconte, Jeil Jung et al. (+1 more)
Extending moiré
graphene beyond twisted
bilayers, helical trilayer
graphene has shown topological bands and correlated states with reshaped moiré periodicity. Here we develop a theoretical framework for helical multilayer
graphene to investigate its supermoiré relaxation and low-energy electronic structure. Using real-space
lattice calculations, we find that relaxation reconstructs the system into locally periodic single-moiré domains, which provide the basis for a continuum description. Within each reconstructed domain, downfolding the first-shell model yields effective
Hamiltonians near the Dirac points that reveal how the low-energy spectrum decomposes into folded Dirac sectors. We further evaluate the valley Chern numbers encoded in these effective
Hamiltonians, obtaining domain-dependent and gate-tunable topological responses consistent with the
lattice calculations. Our results establish a domain-resolved organizing principle for thicker helical
graphene stacks, in which folded Dirac sectors partition the low-energy spectrum, while local stacking families determine the corresponding band character and topological response.
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All authors Kyungjin Shin, Nicolas Leconte, Jeil Jung, Hongki Min
Soft Condensed Matter
Monotile kirigami
Hugo Hiu Chak Cheng and Gary P. T. Choi
Kirigami, the art of paper cutting, has been widely used in the modern design of mechanical metamaterials. In recent years, many kirigami-based metamaterials have been designed based on different planar tiling patterns and applied to different science and engineering problems. However, it is natural to ask whether one can create deployable kirigami structures based on the simplest forms of tilings, namely the monotile patterns. In this work, we answer this question by proving the existence of periodic and aperiodic monotile kirigami structures via explicit constructions. In particular, we present a comprehensive collection of periodic monotile kirigami structures covering all 17 wallpaper groups and aperiodic monotile kirigami structures covering various quasicrystal patterns as well as polykite tilings. We further perform theoretical and computational analyses of monotile kirigami patterns in terms of their shape and size changes under deployment. Altogether, our work paves a new way for the design and analysis of a wider range of shape-morphing metamaterials.
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Mesoscale and Nanoscale Physics
J. Luna-Ramos and A. Martín-Ruiz
We study charge transport through a trivial-topological-trivial junction described by the continuous Qi-Wu-Zhang model, which realizes a two-dimensional Chern-insulating phase. The central region is tuned into the topological regime, while the adjoining leads remain trivial, and an electrostatic barrier of tunable height and width is applied exclusively to the topological slab. By matching wave functions across the interfaces, we obtain the angle- and energy-resolved transmission probability and demonstrate the occurrence of Klein tunneling despite the presence of a bulk spectral gap. Within the continuum Dirac description, this perfect transmission originates from the inversion of the Dirac mass across the junction, which reflects the band inversion of the central layer relative to the trivial leads. In the Qi-Wu-Zhang model considered here, this mass inversion coincides with the transition between trivial and Chern-insulating phases and is accompanied by finite Berry
curvature that governs the nonlinear transport response. The resulting transmission function is then incorporated into a Landauer-Büttiker framework to analyze both linear and nonlinear transport. Closed-form expressions for the linear and nonlinear conductances are derived at zero and finite temperatures. In addition, we investigate the role of dephasing, showing how partial loss of coherence suppresses Fabry-Pérot oscillations while leaving the overall transport trends intact. Finally, we map out the interplay between barrier height, slab thickness, and topological mass parameter, identifying optimal regimes that yield enhanced rectification in the nonlinear response.
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Statistical Mechanics · Cross-listed from q-bio.QM
Information-to-energy trade-offs and the optimal alphabet of polymer replication
Damián G. Hernández
We analyze information transmission in a recently proposed coarse-grained model of
polymer replication by framing it as a communication channel between templates and copies. By calculating the mutual information in the steady-state limit of long chains, we recover the accurate-random phase diagram and establish that the information per-monomer depends solely on template specificity within the accurate regime. Crucially, even in the accurate region, small error fractions lead to substantial information loss due to the nonlinear relationship between errors and mutual information. Examining the information-to-energy cost ratio reveals non-monotonic behavior as a function of monomer alphabet size, with an optimum determined primarily by the per-monomer assembly free energy. For DNA's four-base alphabet, we find that the observed effective assembly energy (at least $14\,k_B T$) places the system far from the information-transmission optimum, suggesting that biological replication may prioritize the suppression of spontaneous random assembly over information-to-energy efficiency. We also characterize achievable rate-fidelity trade-offs using Shannon bounds, providing a theoretical framework for evaluating future proofreading mechanisms in ensemble models.
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Soft Condensed Matter
Hydrodynamic capture and release of a microswimmer by a meniscus corner
Subhasish Guchhait, Harshita Tiwari, Sumesh P. Thampi et al. (+1 more)
Biological microswimmers alter their motility in complex corner geometries, facilitating their survival. However, the dynamical features of low-Reynolds-number swimming at corners remain undefined. Here, we use active droplet microswimmers near a confined meniscus in a microchannel as a model system to study how microswimmer-corner interactions determine swimming patterns. Combining experiments, theory and simulations, we show that pusher-type micrsowimmers are attracted towards a meniscus corner, followed by transient trapping and eventual escape. We demonstrate that hydrodynamic interactions with the wall-interface corner intimately dictate the attraction and trapping or escape of the microswimmer on the basis of its strength. We show that the swimming trajectory at the meniscus corner can be tuned depending on the type of the microswimmer, the corner geometry and the viscosity ratio for the
liquid interface. Our study provides a simple way to manipulate microswimmers by exploiting their hydrodynamic interactions near corner geometries.
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All authors Subhasish Guchhait, Harshita Tiwari, Sumesh P. Thampi, Ranabir Dey
Mesoscale and Nanoscale Physics
Nonequilibrium Kramers Turnover in a Kerr Parametric Oscillator
Daniel K. J. Boneß, Gabriel Margiani, Wolfgang Belzig et al. (+2 more)
Activation processes govern noise-induced switching between long-lived states. In an
equilibrium double well, the thermally activated switching rate exhibits a prefactor with a nonmonotonic dependence on environmental coupling, a foundational crossover known as Kramers turnover. Here, we demonstrate a Kramers turnover analogue in a Kerr parametric oscillator, a driven-dissipative nonlinear system featuring two stable phase states. First, we analytically establish turnover physics in this out-of-
equilibrium setting. There, the strong physical correlation between the activation barrier and intrinsic damping fundamentally obscures the underlying turnover physics. To overcome this limitation, we rescale the rotating-frame dynamics and introduce a tunable effective friction controlled entirely by the parametric drive. This rescaling comes at the cost of a concurrent rescaling of the effective temperature. Exploiting this simultaneous scaling, we leverage the effective temperature to extract the turnover directly from temperature-dependent observations. Subsequently, measuring noise-induced phase slips in a micro-electromechanical device, we observe a distinct crossover in the prefactor's temperature dependence. Our results unambiguously isolate the out-of-
equilibrium turnover regime and highlight that the competition between dissipation and fluctuations profoundly shapes activation dynamics also beyond
equilibrium.
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All authors Daniel K. J. Boneß, Gabriel Margiani, Wolfgang Belzig, Alexander Eichler, Oded Zilberberg
Superconductivity
Observation of field-odd and field-free superconducting diode effects in $\mathrm{Mo}_2\mathrm{C}$ nanoflakes
Wei Gao, Kaixuan Fan, Menghan Li et al. (+8 more)
The superconducting diode effect (SDE) enables nonreciprocal supercurrent flow, holding immense potential for ultra-low-power
quantum electronics. Intrinsic SDE typically requires materials with inherent
symmetry breakings. Here, we report the discovery of SDE in chemical vapor deposition-grown molybdenum carbide ($\mathrm{Mo}_2\mathrm{C}$) nanoflakes, a material traditionally considered centrosymmetric. Strikingly, this system uniquely hosts both field-odd and field-free SDEs. Transport measurements reveal a field-odd SDE with tunable efficiency exceeding 40% at 4 K under a perpendicular in-plane
magnetic field. In a separate sample, a robust field-free SDE persists under zero-field and field-coolings. Out-of-plane field sweeps confirm the intrinsic nature of these phenomena. We propose that domain-boundary supercurrents or charge density wave-like orders drive this unexpected combination of
symmetry breakings. Our findings establish air-stable $\mathrm{Mo}_2\mathrm{C}$ as an ideal platform for nonreciprocal superconducting electronics operating at
liquid-helium temperatures, expanding the search for SDE into nominally centrosymmetric
superconductors.
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All authors Wei Gao, Kaixuan Fan, Menghan Li, Jinhao Cheng, Peng Zhu, Qing Zhang, Shuaishuai Ding, Wenping Hu, Fan Yang, Dechao Geng, Hechen Ren
Materials Science
Operando Characterization of Volume Changes in Lithium-Ion Battery Electrodes during Cycling using Isotope Multilayers
Erwin Hueger, Daniel Uxa, Lars Doerrer et al. (+2 more)
This study reports on advancements in operando characterization of volume changes in lithium-ion battery (LIB) electrode materials during electrochemical cycling. Volume changes are crucial for LIB operation because they are related to the amount of stored energy as well as LIB integrity, performance, and safety. The study introduces a method based on isotope multilayers as active material to track the intrinsic modification of electrode volume in real time under operating conditions with operando
neutron reflectometry. A natGe-73Ge multilayer film is used as a model system to measure the volume change of amorphous germanium electrodes during charging and discharging. Isotope modulation produces a Bragg peak in the
neutron reflectivity pattern, sensitive only to the modification of volume within the active material of the electrode. Battery side reactions, such as the growth and reduction of the solid-electrolyte interphase is excluded. Using this method, the volume modification as a function of Li content x in LixGe can easily be derived from the scattering vector position of the Bragg peak without fitting numerous complex reflectivity patterns. The experiments show a reversible volume change of amorphous germanium of up to 250 percent for x = 3, which appears to be largely independent of current density, cycle number, and the thickness of the individual Ge layers. Also, there are tentative indications that the crystallization and re-amorphization of LixGe are not influencing the volume change.
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All authors Erwin Hueger, Daniel Uxa, Lars Doerrer, Jochen Stahn, Harald Schmidt
Other Condensed Matter · Cross-listed from physics.optics
Electrically-injected room-temperature waveguide polariton laser
Hassen Souissi, Valentin Develay, Maksym Gromovyi et al. (+14 more)
Exciton-polariton
lasers are coherent light sources which do not require the population inversion (transparency) condition to be fulfilled. They have been conceptualized at the end of the XXth century but until now they operate almost exclusively under optical injection, which severely limits the widespread integration of the polariton-based devices implemented so far. Here we tackle this issue by reporting an electrically-pumped
exciton-polariton
laser based on GaN and operating at room temperature in a mode-locked regime. The
laser architecture is close to the geometry of commercial ridge-waveguide GaN
lasers, but based on a bulk GaN active region instead of
quantum wells. Unique features of polariton
lasers are demonstrated, in particular the breakdown of the transparency condition, which enables our polariton
lasers to operate even when only a small fraction (20%) of the cavity length is injected. Moreover, the large polaritonic gain allows for the operation of a short cavity length (60$\mu m$) compared to commercial
lasers. From the very same sample, we also achieve polariton lasing under optical injection, confirming that the doped layers necessary for electrical injection do not prevent strong-coupling nor polariton lasing. Our results open a new perspective for polariton-based devices.
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All authors Hassen Souissi, Valentin Develay, Maksym Gromovyi, Edmond Cambril, Christelle Brimont, Laetitia Doyennette, Guillaume Malpuech, Dmitry Solnyshkov, Blandine Alloing, Sebastien Chenot, Mohamed Al-Khalfioui, Eric Frayssinet, Jean-Yves Duboz, Mingyang Zhang, Jesus-Zuniga Perez, Sophie Bouchoule, Thierry Guillet
Strongly Correlated Electrons
Termination-Controlled Fractionalization and Hybridization at Topological Interfaces in Organic Spin Chains
Khalid N. Anindya and Hong Guo
A single organic
spin platform hosts both dimerized $S=\tfrac{1}{2}$ and effective Haldane $S=1$ sectors, linked by bond-texture inversion. At the junction, the fractional mode is controlled by termination parity: quenched by local fusion at one termination and released as an uncompensated
spin-$\tfrac{1}{2}$-like degree of freedom at the parity-shifted one. Two such internal boundary modes of a finite embedded Haldane domain hybridize with an exponentially decaying splitting, establishing termination parity as a design principle for engineering and coupling fractional boundary modes.
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Statistical Mechanics
G.E. Volovik
In Ref. [1] the statistical structure of the turbulent cascade in the context of non-additive
entropy was considered. Here we suggest that the
vortex line ensemble in the Vinen
quantum turbulence in superfluids is described by the non-extensive Tsallis-Cirto statistics with $\delta=3$. This in particular leads to the temperature, which describes the thermodynamics of the Vinen ensemble, $T\sim mv^2$, where $v$ is the velocity of the flow and $m$ is the mass of the atom of the superfluid
liquid.
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Superconductivity
Spatially-resolved voltage-reversal due to Bernoulli potentials in dissipative Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$
Sharadh Jois, Gregory M. Stephen, Samuel W. LaGasse et al. (+3 more)
We measure magneto-transport and critical currents in Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$
Hall bar devices. Above critical current in an applied
magnetic field, we observe longitudinal differential voltage along one edge comparable in magnitude but opposite in sign to the other edge. This phenomenon is unaffected by reversal of the applied field, and seems unique to devices with invasive voltage contacts. We attribute the source of this behavior to particle-hole
symmetry breaking in moving
vortices and the formation of opposite Bernoulli potentials due to opposing
vortex velocities at the edges where the invasive contacts create hotspots for rapid
vortex nucleation and flux flow. These results are fundamental to the composition and flow of dissipative currents in layered
superconductors.
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All authors Sharadh Jois, Gregory M. Stephen, Samuel W. LaGasse, Genda Gu, Aubrey T. Hanbicki, Adam L. Friedman
Mesoscale and Nanoscale Physics
Photonic Chirality for Braiding and Readout of Non-Abelian Anyons
Netzer Moriya
We propose a cavity-based scheme that uses photonic chirality to control braiding and read out non-Abelian anyons in a fractional
quantum Hall platform. Counter-propagating cavity modes interfere with a classical reference tone to create a rotating pinning landscape whose direction is set by
photon circulation, so that opposite photonic branches drive opposite anyon loops. This realizes a branch-conditioned braid operation and maps the resulting braid response onto cavity intermode coherence. We derive the rotating pinning term and the readout relation at the effective-theory level, identify an operating window set by subgap driving, adiabatic transport, localization, and cavity coherence, and provide phenomenological diagnostics of transport locking. In the minimal four-anyon Ising realization, the leading signal reduces to a calibrated phase; more generally, the same readout structure becomes state dependent when the relative braid operator is non-scalar. The scheme provides a cavity route to braid-sensitive readout of non-Abelian anyons without relying on fragile electronic interference fringes.
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Superconductivity
Competing Constraints on Superconductivity in Thick FeSe films
Ya-Xun He, Xing-Jian Liu, Qun Wang et al. (+6 more)
Superconducting films emerge from the complex interplay of multiple growth parameters, making their optimization challenging. In iron-based
superconductors, compressive strain is known to enhance the transition temperature (Tc) of FeSe films, yet reported Tc values vary widely even on identical substrates, indicating factors beyond strain are critical. Here, we develop a high-throughput off-center pulsed
laser deposition strategy that transforms plume inhomogeneity into combinatorial FeSe film libraries with continuous gradients in
lattice parameter, composition, and disorder. We discover that the maximum Tc does not coincide with the plume center but can shift off-center, revealing a competition between favorable c-axis expansion, stoichiometry, and defect scattering. Systematic characterization of 80 thick films (>50 nm), combined with interpretable machine learning, shows that besides the strong correlate of c-axis
lattice parameter to Tc, the stoichiometry and disorder scattering impose critical constraints on the achievable transition temperature, defining a narrow optimization window rather than a simple monotonic relationship. This framework yields Tconset=17.1 K in thick FeSe films and establishes a general framework combining combinatorial synthesis with machine learning to uncover constrained optimization landscapes in complex functional materials.
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All authors Ya-Xun He, Xing-Jian Liu, Qun Wang, Ting Chen, Hassan Ali, Jia-Ying Zhang, Bao-Juan Kang, Zheng Zhang, Jun-Yi Ge
Mesoscale and Nanoscale Physics
Towards Application of Nanodiamonds for in-situ Monitoring of Radicals in Liquid Phase Chemical Reactions
Emma Herbst, Sebastian Westrich, Alena Erlenbach et al. (+3 more)
In many chemical reactions, short-lived radical intermediates play a crucial role, while detecting such short-lived species in-situ remains challenging. The optically readable electronic
spin of nitrogen-vacancy (NV) centers in diamond is a nanoscale sensor for such radical species: its longitudinal
spin relaxation time (T$_{1}$) reacts to
magnetic fluctuations from the unpaired electrons of radical species in its local environment. In this setting, we demonstrate the successful in-situ detection of the nitroxide radical 2,2,6,6-Tetramethylpiperidinyloxyl (TEMPO) using NV center-based T$_1$ relaxometry after depositing nanodiamonds onto the inner wall of a glass cuvette. A significant concentration-dependent shortening of the relaxation time was observed, from 197\:\textmu s $\pm$ 21\:\textmu s without radical to 66\:\textmu s $\pm$ 30\:\textmu s at a concentration of 1\:M TEMPO. At the same time, the nanodiamonds remain firmly attached to the cuvette even after the solution under investigation has been exchanged. The detection is sensitive in the nanomolar (nM) range and the determined signal-to-noise ratio is between 1.6 and 3.
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All authors Emma Herbst, Sebastian Westrich, Alena Erlenbach, Jonas Gutsche, Maria Wächtler, Elke Neu
Materials Science · Cross-listed from physics.optics
Fast projections of two-dimensional light patterns using acousto-optical deflectors
Robbert Decruyenaere, Clara Tanghe, Senne Van Wellen et al. (+1 more)
Precise and flexible control of structured light fields is essential for applications ranging from optical trapping and
quantum simulation to microscopy and materials processing. Acousto-optical deflectors (AODs) are widely used in these settings due to their high speed, large damage threshold, and ability to generate steerable optical tweezers. Multi-tone driving offers a powerful alternative to slow sequential scanning, enabling the projection of complex patterns with high accuracy as rapid acoustic modulation averages out inter-spot interference. In two dimensions, however, intermodulation between tones in orthogonal AODs can reintroduce coherent artifacts. We present a fast, feedback-free AOD projection scheme based on an incommensurately staggered frequency
lattice that intrinsically suppresses such artifacts. For separable two-dimensional target patterns, our method removes the need for scanning entirely, enabling substantially faster and highly accurate projections. We further extend the approach to non-separable images using a minimal scanning strategy that maintains rather high projection speeds. These results demonstrate that appropriately engineered multi-tone AOD driving offers an efficient and robust route to high-speed, high-fidelity generation of arbitrary intensity patterns.
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All authors Robbert Decruyenaere, Clara Tanghe, Senne Van Wellen, Karel Van Acoleyen
Strongly Correlated Electrons
Hydrodynamics of the viscous electron fluid in cadmium
Xiaodong Guo, Xiaokang Li, Benoît Fauqué et al. (+4 more)
Thanks to electron-electron ($e$-$e$) collisions conserving momentum, metallic electron fluids are viscous. Yet, this viscosity is rarely detectable in bulk transport. Here, we report on the canonical realization of the Gurzhi effect in an elemental three-dimensional metal: cadmium. Using focused ion beam microstructuring to tune the effective thickness, we detected a low-temperature size-dependent resistivity upturn in a finite window sandwiched between ballistic and diffusive regimes. Within this window, the electrical conductivity displays a simultaneous quadratic dependence on both sample size and temperature – fingerprint of a hydrodynamic flow. This leads us to quantify the amplitude and the temperature dependence of kinematic and dynamic viscosity of the electron fluid. In cadmium, in contrast with
graphene and $^3$He, the rate of momentum-conserving $e$-$e$ collisions is not set by the main
Fermi energy, but by Lilliputian energy scales and inter-valley bottlenecks.
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All authors Xiaodong Guo, Xiaokang Li, Benoît Fauqué, Alaska Subedi, Lingxiao Zhao, Zengwei Zhu, Kamran Behnia