Other Condensed Matter · Cross-listed from physics.optics
Velocity-tunable exciton-photon hybridization in cathodoluminescence
Sven Ebel, Martin Nørgaard, Christian Nicolaisen Hansen et al. (+2 more)
Exciton-
photon hybridization is typically realised in geometrically defined optical cavities, where tunability is achieved by modifying either the cavity or the excitonic medium. Here we investigate transition-radiation interferences in suspended subwavelength films resembling a free-electron-defined resonance and explore their interaction with
excitons in transition metal dichalcogenides. We demonstrate that these resonances hybridize with excitonic transitions and can be tuned continuously by varying the electron energy. The resulting detuning depends on both film thickness and electron velocity, establishing the latter as an external and continuous knob for
exciton-
photon coupling. This approach enables tunable hybridization without structural modification and provides a free-electron-driven nanoscale platform for studying
exciton-light interactions.
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All authors Sven Ebel, Martin Nørgaard, Christian Nicolaisen Hansen, N. Asger Mortensen, Sergii Morozov
Materials Science
A biomimetic feedback loop for sustaining self-lubrication and wear resistance
Fuyan Kang, Shilin Deng, Panpan Li et al. (+7 more)
Intelligent materials that self-sense and self-regulate are an emerging frontier in sustainable technology. Here we introduce Cu(Au)/C nanocomposite films that act as bioinspired self-adjusting lubricants. In these films, frictional heating triggers melting and migration of soft metal nanoparticles (NPs) such as Cu or Au along nano-pores to the friction interface, where the metal catalyzes the in-situ formation of ordered carbon nano-structures. Real-time monitoring of friction coefficient, electrical resistance(R), and metal release confirms an autonomous cycle: high friction coefficient generates heat, melting the metal NPs; the migrating metal then lowers friction coefficent by creating low-friction nanostructures, which reduces heat and arrests further migration until friction rises again. This self-limiting feedback enables stable ultra-low friction (~0.04) and an exceptional wear life (>40 km) even in high
vacuum. By utilizing friction-derived heat as an intrinsic activation signal, our system establishes a general paradigm for intelligent, self-regulating materials with applications extending beyond tribology.
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All authors Fuyan Kang, Shilin Deng, Panpan Li, Rui Zhao, Xiaohong Liu, Hongxuan Li, Huidi Zhou, Jianmin Chen, Wengen Ouyang, Li Ji
Soft Condensed Matter
A mechanical bifurcation constrains the evolution of cell sheet folding in the family Volvocaceae
Valens Tribet and Pierre A. Haas
The processes of morphogenesis that give rise to the shapes of organs and organisms during development are often driven by mechanical instabilities. Can such mechanical bifurcations also drive or constrain the
evolution of these processes in the first place? We discover an instance of these constraints in the green algae of the family Volvocaceae. During their development, their bowl-shaped embryonic
cell sheet turns itself inside out. This inversion is driven by a simple wave of
cell wedging in the genus Pleodorina (16-128
cells) and more complex programmes of
cell shape changes in Volvox (~400-50000
cells). However, no species with intermediate
cell numbers (256
cells) have been described. Here, we relate this gap to a mechanical bifurcation: Focusing on the inversion of Pleodorina californica (64
cells), we develop a continuum model, in which the
cell shape changes driving inversion appear as changes of the intrinsic
curvature of an elastic surface. A mechanical bifurcation in this model predicts that inversion is only possible in a subset of its parameter space. Strikingly, parameters estimated for P. californica fall into this possible subset, but those that we extrapolate to 256 or more
cells using allometric observations and a model of
cell cleavage in Volvocaceae do not. Our work thus suggests that the more complex inversion strategies of Volvox are an evolutionary necessity to obviate this bifurcation and indicates more broadly how mechanical bifurcations can drive the
evolution of morphogenesis.
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Soft Condensed Matter
Cracking donuts and sorting lipids: Geometry controls archaeal membrane stability and lipid organization
Felix Frey, Miguel Amaral and An{\dj}ela Šarić
Cells are defined by lipid membranes that differ in their structure across the tree of life. While the membranes of most bacteria and eukaryotes consist of single-headed
bilayer lipids, the membranes of archaea are composed of mixtures of single-headed
bilayer lipids and double-headed bolalipids. Archaeal bolalipids can adopt straight or u-shaped conformations, enabling them - together with
bilayer lipids - to control whether membranes form
bilayer or monolayer structures. Yet, the physical principles governing archaeal membranes remain largely unexplored, especially how membrane structure couples to externally imposed
curvature during membrane remodeling. Here, we perform coarse-grained molecular dynamics simulations of toroidal vesicles to systematically probe the effects of all relevant combinations of mean and Gaussian
curvatures on shape stability and lipid organization. We find that soft
bilayer membranes can sustain all
curvatures induced, whereas rigid bolalipid monolayer membranes either transition to different vesicle shapes or rupture.
Bilayer-mimicking u-shaped bolalipids and
bilayer lipids are spatially accumulated in regions of high mean membrane
curvature independent of Gaussian
curvature. Our work identifies
curvature-composition coupling as a physical signature of archaeal membrane remodeling.
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Materials Science
Decoding the Complexity of Ferroelectric Orthorhombic HfO2: A Unified Mode Expansion Approach
Chenxi Yu, Jiajia Zhang, Xujin Song et al. (+2 more)
The ferroelectricity in $\mathrm{HfO}_2$ thin films is widely attributed to the formation of a polar orthorhombic phase named OIII phase. However, the complexity of OIII phase originated from its low
symmetry becomes an obstacle for studying ferroelectric properties of $\mathrm{HfO}_2$. Here, we developed a unified framework based on
phonon mode expansion for studying ferroelectric $\mathrm{HfO}_2$. In this framework, phase structures, domain walls and switching paths of orthogonal
crystal system can be studied from the same basis of mode analysis. The OIII phase and other orthogonal phases can be represented by the high-
symmetry cubic phase with the excitation of cubic
phonon modes, into which the complexity of orthogonal phases is faithfully coded. To present the capability of this mode expansion approach, we clarified the origin of orthorhombic stability from the energy functional of modes; enumerated inequivalent domain walls and calculated their stable criteria; and summarized all possible switching mechanisms. This unified framework can be used to simplify the study of domain wall structures and transition paths. Furthermore, it can provide a new perspective for ferroelectricity in $\mathrm{HfO}_2$ from
phonon mode analysis.
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All authors Chenxi Yu, Jiajia Zhang, Xujin Song, Fei Liu, Jinfeng Kang
Superconductivity
Hidden Zeeman Field in Odd-Parity Magnets: An Ideal Platform for Topological Superconductivity
Xun-Jiang Luo, Zi-Ting Sun, Xilin Feng et al. (+2 more)
Odd-parity magnets (OPMs) have emerged as a fundamental class of unconventional magnetisms, characterized by time-reversal-preserving non-relativistic
spin splitting (NSS). Despite growing interest, the fundamental understanding of OPMs remains critically incomplete, as previous studies have focused exclusively on NSS while overlooking the intrinsically broken time-reversal
symmetry ($\mathcal{T}$) inherent to
magnetic order. In this work, we reveal that OPMs universally host a hidden Zeeman field rooted in this $\mathcal{T}$-breaking, which fundamentally reshapes their band structure. Through an analytical $f$-wave magnet model, we show that NSS microscopically originates from an emergent gauge field, manifesting as a real-space
spin loop current order. Crucially, the large NSS (eV scale) enables conventional superconductivity to coexist robustly with the hidden Zeeman field, with Zeeman splitting reaches hundreds of meV. This unique band structure establishes OPMs as an ideal platform for topological
superconductors (TSCs), supporting large topological regions. Based on OPMs, we engineer a series of TSCs hosting distinct Majorana boundary modes, including unidirectional Majorana edge states. Our work corrects a fundamental misconception about OPMs and establishes them as a versatile platform for field-free and robust TSCs.
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All authors Xun-Jiang Luo, Zi-Ting Sun, Xilin Feng, Mingliang Tian, K. T. Law
Materials Science
Monolithic integration of diverse crystalline thin films on diamond for near-junction thermal management
Tiancheng Zhao, Tianqi Bai, Yang He et al. (+20 more)
The pursuit of extreme miniaturization and high power in 6G RF front-ends has cast thermal dissipation as the central challenge. Here, we have demonstrated the monolithic integration of functionally distinct single-
crystal thin films, including e̱ta}-Ga2O3, Si, GaN, and LiTaO3, onto a single diamond substrate using a multi-step transfer printing technique. Focusing on the critical e̱ta}-Ga2O3/diamond interface, we achieve an exceptional interfacial thermal conductance (ITC) of 149 MW m-2 K-1 through ultra-high
vacuum (UHV) annealing, creating an atomically sharp interface featuring covalent bonding. Vibrational electron energy-loss spectroscopy (EELS) analysis combining with molecular dynamics (MD) simulations reveal that distinctive interfacial
phonon modes at the e̱ta}-Ga2O3/diamond heterointerface dominate ultrahigh ITC. We experimentally demonstrate that by improving the ITC, the thermal resistance (Rth) of a diamond-based e̱ta}-Ga2O3 MOSFET is driven to a record-low value of 1.58 K mm W-1, underscoring the critical role of interface engineering in near-junction thermal management for diamond-integrated devices. This work demonstrates a scalable, diamond-based monolithic integration platform designed to solve the near-junction thermal challenges in high-power RF front-ends.
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All authors Tiancheng Zhao, Tianqi Bai, Yang He, Wenhui Xu, Xinxin Yu, Ruochen Shi, Zhenyu Qu, Jiaxin Liu, Rui Shen, Haodong Jiang, Yeliang Wang, Jiaxin Ding, Dongchen Sui, Shibin Zhang, Lei Zhu, Ailun Yi, Kai Huang, Min Zhou, Huarui Sun, Zhonghui Li, Peng Gao, Tiangui You, Xin Ou
Mesoscale and Nanoscale Physics
Moiré Ferroelectricity-Driven Band Engineering in Twisted Square Bilayers
Kejie Bao, Rui Shi, Huan Wang et al. (+2 more)
We develop the moiré band theory for M-valley twisted square homobilayers with layer groups $P$-$42m$ and $P$-$4m2$, and propose candidate material realizations. We show that moiré ferroelectricity-originating from sliding ferroelectricity in the untwisted
bilayers-provides an independent control knob for miniband engineering in addition to interlayer tunneling. The competition between these two effects enables controlled switching between layer-resolved
bilayer minibands and an effective single isolated miniband. Remarkably, these systems exhibit an emergent momentum-space nonsymmorphic
symmetry in the absence of external
magnetic fields. Large-scale ab initio calculations identify Cu$_2$WS$_4$ and GeCl$_2$ as representative materials realizing the ferroelectricity- and tunneling-dominated regimes, respectively. Our results establish twisted square homobilayers as a promising platform for correlated band engineering beyond moiré hexagonal systems.
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All authors Kejie Bao, Rui Shi, Huan Wang, Linghao Huang, Jing Wang
Materials Science
Probing a two-dimensional soft ferromagnet Cr$_2$Ge$_2$Te$_6$ by a tuning fork resonator
Hengrui Gui, Zekai Shi, Jiawen Zhang et al. (+3 more)
Magnetic anisotropy encodes key information about the free-energy landscape of
magnetic materials, but its quantitative characterization often requires probes beyond conventional magnetometry. A quartz tuning-fork resonator provides direct access to the magnetotropic susceptibility. Here we use this technique to investigate the
magnetic anisotropy of the layered ferromagnet Cr$_2$Ge$_2$Te$_6$. The temperature-, field-, and angle-dependent responses are consistently described by a quasi-two-dimensional (2D) easy-axis
ferromagnetic model. In particular, the
evolution of the magnetotropic susceptibility reveals how the angular profile changes from a conventional cos(2$\theta$) form to a pronounced dip structure as the magnetization approaches directional saturation. These results establishCr$_2$Ge$_2$Te$_6$ as an ideal reference system for tuning-fork-based magnetotropic measurements. More broadly, they provide a useful framework for distinguishing
spin-origin anisotropy from orbital magnetism, as in the case of CsV3Sb5. Our work demonstrates that tuning-fork resonators offer a sensitive thermodynamic probe of the rotational stiffness of magnetization in anisotropic low-dimensional magnets.
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All authors Hengrui Gui, Zekai Shi, Jiawen Zhang, Yu Liu, Huiqiu Yuan, Lin Jiao
Strongly Correlated Electrons
Lee–Yang Zeros and Pseudocritical Drift in J-Q Néel Antiferromagnet–Valence-Bond Solid Transitions
Chunhao Guo, Zhe Wang, Danhe Wang et al. (+3 more)
Square-
lattice J-Q models provide a sign-problem-free setting for probing the
quantum phase transition between Néel antiferromagnet and columnar valence-bond solid. We analyze this transition through the scaling of Lee–Yang zeros, computed within
stochastic series expansion
quantum Monte Carlo by reweighting configurations sampled near criticality in the presence of complex source fields.
Benchmark studies of the dimerized Heisenberg model and the checkerboard J-Q model validate the method, yielding stable \(\mathrm{O}(3)\) critical scaling in the former and clear spacetime-volume scaling in the latter, as expected for a first-order transition. Applying the same analysis to the J-Q models, we find a pronounced and systematic drift of the leading-zero scaling with increasing system size, consistent with an extended pseudocritical regime. The Lee–Yang scaling implies an effective scaling dimension \(\Delta_{\phi}\) of the \(\mathrm{SO}(5)\) order-parameter field that decreases with size and is consistent with vanishing in the thermodynamic limit. Such behavior lies below the scalar unitarity bound of any
unitary relativistic conformal field theory in \(2{+}1\) dimensions and enforces inverse spacetime-volume scaling of the zeros, the hallmark of a first-order transition. These results support a weakly first-order interpretation of the Néel–VBS transition and establish the finite-size Lee–Yang zeros as a sensitive,
symmetry-resolved diagnostic of pseudocriticality and transition order in the J-Q family.
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All authors Chunhao Guo, Zhe Wang, Danhe Wang, Zenan Liu, Haiyuan Zou, Zheng Yan
Superconductivity
Probing the Meissner effect in single crystals of $\mathbf{Bi_2Sr_2Ca_2Cu_3O_{10+\delta}}$ via wide-field quantum microscopy under high pressure
Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi et al. (+5 more)
We investigated the pressure dependence of the superconducting transition temperature ($T_{\rm c}$) in optimally doped Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ (Bi-2223) single
crystals using different pressure-transmitting media. Previous high-pressure studies have reported conflicting behaviors, ranging from a resurgence of $T_{\rm c}$ of optimally doped Bi-2223 in fluid media to an insulating-like transition in solid media. However, a direct comparison of the effects of different pressure-transmitting media is lacking. Here, we employed wide-field
quantum microscopy based on nitrogen-vacancy centers to probe the
magnetic response under high pressure, utilizing cBN and KBr as media. We observed that a diamagnetic response near 70 K, indicative of the superconducting transition, persisted up to 23 GPa in KBr, whereas it disappeared above 11 GPa and 70 K in cBN. These results demonstrate the high sensitivity of Bi-2223 to the pressure environment and highlight the critical role of hydrostatic pressure in cuprate
superconductors.
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All authors Masahiro Ohkuma, Ryo Matsumoto, Shintaro Adachi, Shinobu Onoda, Takao Watanabe, Kenji Ohta, Yoshihiko Takano, Keigo Arai
Materials Science
Persistent incommensurate amorphous/crystalline meta-interfaces enable engineering-grade superlubricity
Wan Wang, Zijun Ding, Panpan Li et al. (+7 more)
Friction dissipates a substantial portion of global energy, motivating the pursuit of superlubricity, a state of near-zero friction, in real-world systems. Conventional approaches rely on crystalline
lattice mismatch to suppress periodic energy barriers, but real interfaces invariably contain defects, edges and grain boundaries that restore high-friction states. Here we introduce a materials-agnostic strategy based on amorphous/crystalline heterointerfaces to achieve robust superlubricity under engineering-relevant conditions. Using diamond-like carbon (DLC) and crystalline MoS2 as a model system, we show through experiments and atomistic simulations that their interface remains incommensurate at all orientations and exhibits vanishing energy barriers during friction. In contrast, twisted MoS2
bilayers readily reorient into commensurate, high-friction states. We scale this effect by fabricating
laser-patterned arrays of DLC/MoS2 meta-contacts reinforced with Ti3C2Tx MXene, forming hierarchical interfaces that sustain a friction coefficient of ~0.008 over 100000 cycles under combined extreme conditions: millimetre-scale contact size, 12.7 GPa contact pressure and RH 40% air. This unprecedented performance arises from four synergistic factors: intrinsic incommensurability at amorphous/crystalline interface, the
rigidity of DLC support, MXene-based mechanical reinforcement and normalized load distribution by
geometric patterning. These findings establish a general design paradigm that extends structural superlubricity from nanoscale model systems to practical technologies for sustainable engineering.
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All authors Wan Wang, Zijun Ding, Panpan Li, Wanying Ying, Hongxuan Li, Xiaohong Liu, Huidi Zhou, Jianmin Chen, Wengen Ouyang, Li Ji
Statistical Mechanics · Cross-listed from astro-ph.SR
The Chandrasekhar's Conditions as Equilibrium and Stability of Stars in a Universal Three-Parameter Non-Maxwell Distribution
Wei Hu and Jiulin Du
The idea of the Chandrasekhar's conditions as
equilibrium and stability of
stars is revisited with a new universal three-parameter non-Maxwell distribution. We derive the maximum radiation pressures in the non-Maxwell distribution for a gas
star and a centrally-condensed
star, respectively, and thus we generalize the Chandrasekhar's conditions in a Maxwellian sense. By numerical analyses, we find that the non-Maxwellian distribution usually reduces the maximum radiation pressures in both a gas
star and a central condensed
star as compared with that cases if the gas is assumed to be a Maxwellian distribution.
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Statistical Mechanics · Cross-listed from q-bio.PE
Diverse communities promote the coexistence of closely-related strains through emergent equalization and stabilization
Naven Narayanan Venkatanarayanan and Akshit Goyal
Microbial communities harbor extensive fine-scale diversity: closely-related strains of the same species coexist alongside many distantly-related taxa. Yet strain coexistence remains poorly understood, largely because most studies neglect the diverse communities in which strains are embedded. Here we combine community ecology and statistical physics to study the dynamics of closely-related strains in a community context. We demonstrate that in a diverse community, indirect interactions between strains – mediated through the surrounding community members – can be as strong as direct ones. These community-mediated feedbacks cause conspecific strains to behave as if they have correlated growth rates and reduced competition. Using modern coexistence theory, we show that these effects correspond to equalizing and stabilizing mechanisms which together promote strain coexistence. The same equalizing and stabilizing mechanisms also qualitatively transform strain abundance correlations: strains that compete strongly and show negative correlations in isolation instead show positive correlations in a community, appearing mutualistic despite being competitors. Our results demonstrate that strain dynamics are emergent consequences of the surrounding community, and that capturing community feedbacks does not require the full interaction network; only a small number of emergent parameters.
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Materials Science
Domain Walls Stabilized by Intrinsic Phonon Modes and Engineered Defects Enable Robust Ferroelectricity in HfO2
Chenxi Yu, Jiajia Zhang, Xujin Song et al. (+6 more)
Ferroelectric $\mathrm{HfO}_2$ has attracted extensive research interest for its applications in AI era. The domain walls play a crucial role in phase structure stabilization and polarization switching of ferroelectric $\mathrm{HfO}_2$, however, a thorough understanding is still lacking. Here, we developed a unified framework based on
phonon mode expansion to systematically study the effects of
phonon modes and defects on domain wall structures. Using this approach combined with first-principle calculations, we revealed that the interface
phonon modes play a key role in stability of domain walls; defects pin and stabilize ferroelectric domains, which in turn stabilizes the metastable orthorhombic phase and facilitates polarization switching. This provides an insight from the microscopic physics origin into the enhanced ferroelectricity in $\mathrm{HfO}_2$ by doping and defect engineering. Furthermore, the theoretically predicted domain structures and defect distributions were observed in La-doped $\mathrm{HfO}_2$ ferroelectric films by EELS and STEM experiments, which confirms the validity of our findings.
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All authors Chenxi Yu, Jiajia Zhang, Xujin Song, Dijiang Sun, Shangze Li, Fei Liu, Xiaoyan Liu, Wei Xi, Jinfeng Kang
Materials Science
Loss of altermagnetic order and smooth restoration of Kramers' spin degeneracy with increasing temperature in CrSb and MnTe
Christopher D. Woodgate, Nabil Menai, Arthur Ernst et al. (+1 more)
We describe how thermally induced
spin fluctuations modify the electronic structures of two prototypical altermagnets, CrSb and MnTe, via application of the disordered local moment picture. For both materials, our self-consistent, ab initio calculations demonstrate that local
magnetic moments persist on Cr and Mn atoms in their paramagnetic states, necessitating a
spin-polarised description of the electronic structure even above the Néel temperature, $T_\mathrm{N}$. Moreover, Kramers'
spin degeneracy, which is broken for both materials in their altermagnetic ground states, is shown to be smoothly restored - on the average - as the local moments thermally disorder. In metallic CrSb, this occurs at temperatures well below $T_\mathrm{N}$ and the signature effects of its altermagnetism are lost as the
magnetic disorder induces heavy smearing of strongly dispersive electronic states around the
Fermi energy. By contrast, in semiconducting MnTe, with its band gap largely unaffected by
magnetic disorder, the
spin degeneracy only returns at temperatures close to and above $T_\mathrm{N}$. We quantify the temperature dependence of the altermagnetic order parameter and the underlying electronic structures of both materials, with implications for their
spin transport and spectroscopic properties.
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All authors Christopher D. Woodgate, Nabil Menai, Arthur Ernst, Julie B. Staunton
Soft Condensed Matter
Polarization Plasticity of Ferroelectric Nematics: a case of Electrostatic Frustration in Simple Planar Electrode Cells
Stefano Marni, Federico Caimi, Luca Casiraghi et al. (+5 more)
Because of their spontaneous bulk polarization, ferroelectric nematic
liquid crystals can be easily brought by surface coupling or confinement in a state in which the accumulation of bound charges becomes incompatible with polar order, creating frustration. This condition also occurs in the simplest
cells with parallel uncoated metal electrodes where we find that the polarization charge accumulating on the electrodes is proportional to the applied voltage for $\Delta V< V_{sat}$, a threshold value independent of
cell thickness. We show that below $V_{sat}$, frustration drives the system into a regime of polarization plasticity, in which nematic ordering is preserved and the nematic director remains perpendicular to the electrodes, while instead the polarization is reduced to cancel the internal electric field. In this regime, the kinetics of bound charge reversal becomes independent from $\Delta V$. The observations are consistent with a model in which the system splits into antipolar tubular domains of mesoscale diameter extending from electrode to electrode, in which the polarization retains its unconstrained
equilibrium value, separated by pure polarization-reversal walls.
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All authors Stefano Marni, Federico Caimi, Luca Casiraghi, Jordan Hobbs, Calum J. Gibb, Richard Mandle, Giovanni Nava, Tommaso Bellini
Materials Science
Electric-Field-induced Two-Dimensional Fully Compensated Ferrimagnetism and Emergent Transport Phenomena
Jin-Yang Li, Yong-Kun Wang, Ying Zhang et al. (+2 more)
The recent discovery of altermagnetism has demonstrated that
spin-split electronic band structures can emerge in
magnetic systems with zero net magnetization. In contrast, fully compensated ferrimagnetic (fFIM) systems remain far less explored, despite exhibiting similar characteristics such as vanishing magnetization and
spin-split bands. Here, based on first-principles calculations combined with theoretical analysis, we demonstrate that monolayer CoS and CoSe can be driven into fFIM states by an external electric field. These materials possess collinear
antiferromagnetic ground states with out-of-plane Néel vectors, and their electronic bands are
spin degenerate due to $\mathcal{PT}$
symmetry. When an out-of-plane electric field is applied, $\mathcal{PT}$
symmetry is broken, inducing fFIM states with pronounced
spin splitting. Moreover, we show that the resulting fFIM states host fully
spin-polarized currents, anomalous
Hall effects, and magneto-optical Kerr and Faraday effects. Our results establish monolayer CoS and CoSe as promising platforms for electric-field-controlled fFIM states and spintronic applications.
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All authors Jin-Yang Li, Yong-Kun Wang, Ying Zhang, Si Li, Wen-Li Yang
Mesoscale and Nanoscale Physics · Cross-listed from math-ph
The Zak phase in topologically insulating chains: invariants and limitations
Federico Manzoni, Domenico Monaco and Gabriele Peluso
In this work we investigate the topological content of the Zak phase in one-dimensional translation-invariant topological
insulators endowed with time-reversal, particle-hole and/or
chiral symmetries, extending results from \cite{Monaco_2023}. We analyze the extent to which the Zak phase captures the
topology of all Altland–Zirnbauer–Cartan (AZC)
symmetry classes in $1$D. Building on the framework of fibered
Hamiltonians and spectral projections, we construct symmetric Bloch bases adapted to the discrete
symmetries of the system and define a $\mathbb{Z}_2$-valued topological invariant $\mathrm{I}^{(\mathrm{AZC-class})}(H)$ obtained from the abelian Zak phase. Moreover, we demonstrate that in
symmetry classes admitting a quaternionic structure, i.e. anti-
unitary symmetries squaring to minus the identity, the Zak phase is further constrained, leading to the vanishing of the $\mathbb{Z}_2$ invariant mentioned above. This highlights the sensitivity of the Zak phase to additional
geometric structures of the
manifold of occupied energy states, as well as its limitations in being an effective marker for topological phases of insulating chains. As an example, we discuss the case of generalized Kitaev chains with arbitrary finite-range hopping and single or multiple
chiral channels, and show how the Zak phase only retains partial information about their different topological phases.
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Other Condensed Matter
Measuring impurity-induced shifts in Coulomb crystallization
Mingyao Xu, Aaron A. Smith, Leonid Prokhorov et al. (+2 more)
We report a laboratory measurement of how
impurities shift Coulomb crystallization in a strongly interacting ionic system. This is achieved by using
laser cooled Ca$^+$
crystals doped with a controlled number of Xe$^{12+}$ highly charged ions. We find that the crystallization threshold is unchanged at low
impurity concentration, but shows a clear crossover once the
impurity content becomes sufficiently large, after which the shift grows approximately linearly. Complementary measurements reveal that this global effect originates from a local pinning of the
crystal around the
impurities. We further show how the measured shift could impact standard models of crystallization in white
dwarfs and
neutron stars. Our results provide an experimental route to incorporating
impurity effects into models of multicomponent Coulomb matter, relevant to
stellar crystallization and strongly coupled
plasmas.
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All authors Mingyao Xu, Aaron A. Smith, Leonid Prokhorov, Vera Guarrera, Giovanni Barontini
Soft Condensed Matter
Cage Breaking Far from Equilibrium
Jared Popowski, Nico Schramma, Edan Lerner et al. (+1 more)
Active matter can flow and yield under conditions where passive matter jams and slows down, as self-propulsion significantly modulates particle escape from local cages. How activity microscopically reshapes the caging environment to produce this effect, however, remains poorly understood. Here we study a minimal active-matter model of cage breaking: three distinguishable self-propelling disks under circular confinement. This simple setting allows us to construct an entropic landscape for rearrangements and to compare it exactly with its
equilibrium counterpart. At low activity the landscape is effectively bistable, whereas at high activity it develops additional metastable basins associated with frustrated clusters at the boundary. We quantify the system's departure from
equilibrium and show that cage breaking is fastest when the persistence length matches the particle radius, linking a
geometric microscopic scale to the enhanced dynamics of active glasses. Extending the landscape to two dimensions reveals circulating probability currents, and a Markov-state description shows that detailed balance is broken both in the continuous landscape dynamics and in the coarse-grained transitions between entropic basins. Our results provide a minimal microscopic framework for understanding how activity reshapes caging, relaxation, and irreversibility in dense nonequilibrium matter.
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All authors Jared Popowski, Nico Schramma, Edan Lerner, Maziyar Jalaal
Materials Science
Bond-selective modulation of scalar spin chirality in strained Mn4N
Xin Liu, Mingyue Zhao, Shun Niu et al. (+10 more)
Scalar
spin chirality (SSC) underlies a variety of Berry-phase-driven transport phenomena in noncoplanar magnets. Mn4N is a unique ferrimagnetic system in which both collinear and noncoplanar
magnetic configurations have been reported at different
lattice parameters, featuring vanishing and finite SSC, respectively. However, the microscopic mechanism governing the competition between these
magnetic states and the associated modulation of SSC remains unclear. This issue is particularly important for Mn4N because its high
magnetic ordering temperature (TN = 740 K) provides an attractive platform for exploring
chiral magnetic states and their associated topological functionalities at elevated temperatures. Here, using first-principles calculations, we investigate the strain-driven
evolution of the
magnetic ground state and SSC in Mn4N and uncover the microscopic origin of the collinear-to-noncoplanar
magnetic transition. We demonstrate that tensile strain continuously stabilizes the noncoplanar configuration and enhances SSC, as quantified by the magnitude of the chirality-order vector. Orbital-resolved
crystal orbital Hamilton population and charge-density-difference analyses reveal that strain selectively weakens the Mn3c-N hybridization while preserving direct Mn3c-Mn3c interactions, leading simultaneously to the activation of the Mn3c in-plane
magnetic moment and the suppression of N-mediated
ferromagnetic superexchange between nearest-neighbor Mn3c atoms. This bond-selective electronic response governs the
magnetic ground state and consequently controls the emergence and enhancement of SSC in Mn4N. Our work establishes bond selectivity as an effective strategy for engineering SSC in high-temperature ferrimagnetic materials.
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All authors Xin Liu, Mingyue Zhao, Shun Niu, Yu Liu, Yang Li, Jiayao Zhu, Yiwen Zhang, Fengxian Ma, Dewei Zhao, Guoke Li, Li Ma, Congmian Zhen, Denglu Hou
Disordered Systems and Neural Networks
Machine learning cannot decarbonise the subsurface until it can be audited
Hannah P. Menke, Ahmed H. Elsheikh, Lingli Wei et al. (+2 more)
Geological CO2 storage, geothermal energy and underground hydrogen storage depend on irreversible or high-cost decisions made with sparse data and incomplete physical understanding. Machine learning (ML) increasingly informs these decisions, yet methods are usually judged on predictive accuracy rather than on whether their outputs can be trusted, traced and acted upon. We argue that subsurface ML should be designed as decision infrastructure with shared systems that carry calibrated uncertainty and provenance from observation to operating decision. We propose a decision-readiness checklist, an audit-trail workflow for monitoring updates, and
benchmark designs that score models by the decisions they support. We identify validation needs shared across the three technologies, and the data-access and governance steps needed for ML to support regulatory and investment decisions.
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All authors Hannah P. Menke, Ahmed H. Elsheikh, Lingli Wei, Nanzhe Wang, Andreas Busch
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Non-equilibrium quantum plasmonics in nanoparticle-on-mirror nanocavities
Artur Avdizhiyan, Ilya Razdolski and Anton Yu. Bykov
We develop a novel approach to ultrafast optical modulation of
quantum-mechanical phenomena at the interface of plasmonic metals. Focusing on efficient and versatile nanoparticle-on-mirror plasmonic nanocavities, we discuss indirect control of plasmonic properties through
laser-induced ballistic hot electron injection. Overcoming the limitations precluding the observations of
laser-driven mesoscopic phenomena in the time domain with state-of-the-art amplified sources, our proposed experimental approach can be readily realized without irreversible optical damage and holds immense potential for the future development of ultrafast electrodynamics in nanogaps, applications in photochemistry and nanoscale control of
quantum emitters. Agreeing with the results of numerical simulations, an intuitive microscopic model for the proposed time-dependent mesoscopic electrodynamics facilitates the analysis of the temperature-induced modulation of
quantum plasmonic properties in a broad parameter space. Our work expands the realm of
quantum nanophotonics onto non-
equilibrium electronic systems and facilitates the development of ultrafast methods in active plasmonics.
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Other Condensed Matter
Demonstration of AI-Assisted Scientific Workflow on Canonical Benchmarks
Kin Hung Fung
We present a fully reproducible demonstration of an AI-assisted scientific workflow designed for a broad physics, mathematics, and computer-science readership. The initial project artifact stack was generated from one single user
prompt and then reviewed and curated for submission by the human author. Rather than claiming a new scientific discovery, the manuscript uses canonical
benchmark problems with exact, manufactured, or independently checkable answers. The analytical component starts from the one-dimensional
quantum harmonic oscillator, derives its dimensionless form, and validates finite-difference eigenpairs against exact Hermite-function
benchmarks. The numerical partial-differential-equation component solves a heat equation with a known modal solution and a Poisson problem verified by a manufactured solution, with explicit convergence studies. The inverse-modeling component fits synthetic damped-oscillation data by nonlinear least squares and quantifies parametric uncertainty by bootstrap resampling. The computational-science component compares dense and sparse eigensolvers and contrasts direct and iterative sparse linear solvers, with careful interpretation of machine-dependent timing data. Taken together, the results show that contemporary AI can already serve as a useful scientific copilot for derivation, implementation, validation, visualization, and manuscript preparation, provided that each stage is constrained by
benchmark theory, explicit verification, and transparent artifacts. The demonstration is therefore relevant not because the underlying science is novel, but because it offers a concrete template for trustworthy AI use in technical research practice.
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Materials Science
Ductility and Brittle Fracture of Tungsten by Disconnection Pile-up on Twin Boundaries
Omar Hussein, Nicolas Bertin, Jakub Veverka et al. (+5 more)
Refractory body-centered cubic (BCC) metals and
alloys are of extraordinary importance in modern technological and structural applications. However, their wider adoption in science and technology is severely restricted by low-temperature brittleness, quantified by an unacceptably high value of the brittle-to ductile transition temperature (DBTT). The DBTT of these
alloys is known to depend strongly on the particular microstructure of the material following mechanisms that are not well understood. Here we apply cross-scale molecular dynamics (MD), a simulation approach that preserves full atomic resolution while capturing the collective
evolution of dislocations, twins, and cracks in near-micron-scale volumes, to investigate ductility and fracture in single-
crystal tungsten pillars as a function of initial defect microstructure, deformation conditions, and temperature. The simulations reveal a sequence of microscopic processes conducive to failure: dislocation starvation, nucleation and growth of twins, pinning of the twin boundaries at surface asperities, resulting in disconnection pile-ups that trigger crack nucleation and propagation at low macroscopic stresses along incoherent boundary segments. By resolving these processes within a single atomistic framework, our simulations connect defect-level dynamics to macroscopic fracture behavior and identify microstructural pathways capable of shifting the DBTT through targeted promotion or suppression of the underlying deformation mechanisms.
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All authors Omar Hussein, Nicolas Bertin, Jakub Veverka, Tomas Oppelstrup, Jaime Marian, Fadi Abdeljawad, Shen J. Dillon, Timofey Frolov
Quantum Gases
Quantum simulation of the Haldane phase using open shell molecules
Suman Aich, Ceren B. Dag, H.A. Fertig et al. (+2 more)
Dipolar molecules in optical traps are a versatile platform for studying many-body phases of
quantum matter in the presence of strong and long-range interactions. The dipolar interactions in such setups can be enabled by microwave driving opposite parity rotational levels of the molecules. We find that the regime where the $N=0,J=1/2,F=1$ state is coupled to the $N=1,J=3/2,F=2$
manifold with circularly polarized microwaves, in the presence of a small
magnetic field, can lead to
spin-1
quantum magnetic Hamiltonians, due to the decoupling between electron
spin and orbit, that is unique to the $^2\Sigma$ ground state molecules. We demonstrate that in one dimension, the phase diagram associated with this
Hamiltonian, computed via tensor network methods, hosts the celebrated Haldane phase. We find that the Haldane phase persists even in the presence of SU(3) correction terms that break the SU(2)
algebra of the
Hamiltonian. We discuss the feasibility of the proposed scheme for $^2\Sigma$ molecules with large rotational constants such as the directly
laser cooled molecule MgF for future experiments.
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All authors Suman Aich, Ceren B. Dag, H.A. Fertig, Debayan Mitra, Babak Seradjeh
Statistical Mechanics · Cross-listed from physics.optics
Nonlinear optical thermodynamics from a van der Waals-type mean-field theory
Meng Lian, Zhongfei Xiong, Yuntian Chen et al. (+1 more)
Optical thermodynamics offers a distinctive framework for understanding complex phenomena in multimode systems, yet standard ideal-gas-like formulation neglects the effect of nonlinear interaction on thermodynamic quantities, significantly restricting its range of validity. Here, we overcome this limitation by developing a mean-field thermodynamic theory that incorporates the nonlinear renormalization of the mode spectrum. The resulting nonlinear equation of state, analogous to that of the van der Waals for gases, enables the prediction of power-dependent mode localization and the description of optical cooling and heating in photonic Joule-Thomson expansion. Our work establishes a unified thermodynamic perspective on the nonlinear control and transport of optical waves.
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All authors Meng Lian, Zhongfei Xiong, Yuntian Chen, Jing-Tao Lü
Materials Science
Hybrid Tribo/piezoelectic Electrospun Nanofibers for Energy Harvesting Enhancement in Flexible Electronics
Hao Zhang, Yurong He, Yaofeng Jin et al. (+4 more)
Triboelectric nanogenerators or TENGs and piezoelectric nanogenerators or PENGs have emerged as promising platforms for harvesting mechanical energy and converting it into electrical energy for powering flexible electronic devices. However, the material selection and structure design of such hybrid nanogenerator, and mechanisms of energy output still remain challenges. In this work, electrospinning is employed for the fabrication of nanofibers, particularly polyvinylidene fluoride or PVDF based nanofibers, due to its capability to generate high beta phase contents that effectively increase the piezoelectric performance of the PVDF friction layer, thereby enhancing the overall electrical performance for flexible electronics by merging tribo-piezoelectric power. Furthermore, various concentrations carbon nanotubes or CNT or
graphene nanosheets or GNS are individually incorporated into the PVDF solution as nanofillers or NF to enhance the piezoelectric responses of the PVDF based nanofibers. The introduction of nanofillers is found to not only alter the fiber diameter but also modify the surface roughness of the electrospun nanofibers, and thus, enhancing the triboelectric effect. In addition, the output performance of the fabricated nanogenerator is predominantly governed by the piezoelectric effect rather than triboelectric effect, as the electrical output shows a strong positive correlation with the beta phase content of PVDF based nanofibers: the highest beta phase content reached to 85.3 percent and consistently resulted in the optimal energy output of 1.133 watt per meter square. Notably, the power density achieved by the prototype device reaches to the level of watt/m2, representing a substantial improvement compared with that of the conventional TENGs or PENGs reported to date, providing expanded opportunities for flexible electronic devices
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All authors Hao Zhang, Yurong He, Yaofeng Jin, Hui Wang, Wanqi Ye, Lidong Chen, Kaiyang Zeng
Mesoscale and Nanoscale Physics · Cross-listed from cs.CV
From Artefact to Insight: Efficient Low-Rank Adaptation of BrushNet for Scanning Probe Microscopy Image Restoration
Ziwei Wei, Yao Shen, Wanheng Lu et al. (+2 more)
Scanning Probe Microscopy or SPM offers nanoscale resolution but is frequently marred by structured artefacts such as line scan dropout, gain induced noise, tip convolution, and phase hops. While most available methods treat SPM artefact removal as isolated denoising or interpolation tasks, the generative inpainting perspective remains largely unexplored. In this work, we introduce a
diffusion based inpainting framework tailored to scientific grayscale imagery. By fine tuning less than 0.2 percent of BrushNet weights with rank constrained low rank adaptation (LoRA), we adapt a pretrained
diffusion model using only 7390 artefact, clean pairs distilled from 739 experimental scans. On our forthcoming public SPM InpBench
benchmark, the LoRA enhanced model lifts the Peak Signal to Noise Ratio or PSNR by 6.61 dB and halves the Learned Perceptual Image Patch Similarity or LPIPS relative to zero-shot inference, while matching or slightly surpassing the accuracy of full retraining, trainable on a single GPU instead of four high-
memory cards. The approach generalizes across various SPM image channels including height, amplitude and phase, faithfully restores subtle structural details, and suppresses
hallucination artefacts inherited from natural image priors. This lightweight framework enables efficient, scalable recovery of irreplaceable SPM images and paves the way for a broader
diffusion model adoption in nanoscopic imaging analysis.
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All authors Ziwei Wei, Yao Shen, Wanheng Lu, Ghim Wei Ho, Kaiyang Zeng