Statistical Mechanics · Cross-listed from q-bio.PE
Predicting success of cooperators across arbitrary heterogeneous environmental landscapes
Amir Kargaran, Kamran Kaveh and Krishnendu Chatterjee
Cooperation is central to the organization of complex biological and social systems. Most theoretical models assume homogeneous environments; in reality, populations inhabit spatially varying landscapes in which the payoffs of cooperation differ across space. Here, we introduce a general framework for the
evolution of cooperation in complex, heterogeneous environments where the benefit of cooperation depends on local environmental quality. Cooperators in environmentally rich sites confer greater benefits than those on poor sites. We show that whether heterogeneity promotes or suppresses cooperation is determined primarily by the spatial organization of environmental states. Across arbitrary environmental landscapes, a single quantity, the spatial correlation index (SCI), predicts the fixation probability of cooperators. Under weak selection, segregated environments enhance cooperation, whereas highly intermixed, checkerboard-like landscapes suppress it. Beyond fixation probabilities, environmental organization also controls evolutionary timescales: segregated landscapes generate long-lived metastable coexistence, whereas intermixed landscapes lead to faster but less successful fixation of cooperators. Together, these results provide a unifying description of how spatial environmental heterogeneity shapes the
evolution of cooperation and suggest measurable predictors of cooperative success in biological and social settings.
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Mesoscale and Nanoscale Physics
Chiral electron-fluxon superconductivity in circuit quantum magnetostatics
Adel Ali and Alexey Belyanin
We investigate electron paring in two-dimensional electron systems mediated by the
vacuum fluctuations of a quantized
magnetic flux generated by the inductor of an LC resonator. The interaction induces long-range attractive interactions between angular momentum states which lead to pairing in a broad class of materials with critical temperatures of few Kelvin or even higher, depending on the field-covered area. The induced state is a pair-density wave topological
chiral superconductor. The proposed platform in
circuit QED environment offers a tunable promising tool for engineering electron interactions in two-dimensional systems to create new
quantum phases of matter.
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Materials Science · Cross-listed from physics.app-ph
Thermal Characterization of Buried Interfaces in Multilayer Heterostructures via TDTR with Periodic Waveform Analysis
Mingzhen Zhang, Puqing Jiang and Ronggui Yang
Accurate evaluation of buried thermal interfaces is vital for understanding and optimizing heat dissipation in wide- and ultra-wide-bandgap (WBG/UWBG)
semiconductor devices. Conventional time-domain thermoreflectance (TDTR) typically probes only near-surface transport due to its restricted modulation frequency range. Here, we employ a frequency-tunable periodic waveform analysis TDTR (PWA-TDTR) technique to perform depth-resolved thermal measurements on three representative systems: epitaxial {\epsilon}-Ga2O3/SiC, GaN/Si, and mechanically bonded GaN/diamond. By combining broadband multi-frequency probing with sensitivity-guided joint fitting, we quantitively determine interfacial thermal conductance, layer-specific thermal conductivity, and volumetric heat capacity, without requiring destructive sample preparation. The results reveal that the buried Ga2O3/SiC interface exhibits weak
phonon transmission due to acoustic mismatch; the transition layers in GaN/Si act as
phonon-impedance gradients that redistribute heat flux; and the GaN/diamond boundary remains the dominant thermal bottleneck despite diamond's ultrahigh bulk conductivity. These findings demonstrate that the modulation frequency in PWA-TDTR functions as a tunable probe of depth-dependent
phonon transport, directly linking frequency-domain thermal response to interfacial energy transmission. Overall, this work positions PWA-TDTR as a versatile platform for investigating buried nonmetal-nonmetal interfaces in next-generation high-power and optoelectronic materials.
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Materials Science · Cross-listed from physics.app-ph
Anisotropic Thermal Characterization of Suspended and Spin-Coated Polyimide Films Using a Square-Pulsed Source Method
Bingjiang Zhang, Dihui Wang, Tao Chen et al. (+2 more)
Polyimide (PI) thin films are widely used in advanced technologies, yet accurate characterization of their thermal properties remains challenging, as evidenced by significant inconsistencies in reported data and an incomplete understanding of heat transfer mechanisms. In this study, we employ an optical Square-Pulsed Source (SPS) technique to simultaneously measure the in-plane and cross-plane thermal conductivities, as well as the volumetric heat capacity, of PI thin films. SPS is a pump-probe method that utilizes a square-wave-modulated pump
laser to induce periodic heating and a probe
laser to detect the thermoreflectance response. Thermal properties are extracted by analyzing amplitude signals across multiple modulation frequencies and
laser spot sizes. Measurements were conducted on both suspended commercial PI films and
spin-coated PI films on fused silica substrates. The results show that
spin-coated films exhibit higher cross-plane thermal conductivity and lower anisotropy compared to suspended films, which we attribute to differences in molecular orientation and substrate interactions. These findings provide new physical insights into anisotropic heat transport in
polymer thin films and demonstrate the SPS technique as a robust tool for probing microscale thermal phenomena in soft materials.
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All authors Bingjiang Zhang, Dihui Wang, Tao Chen, Heng Ban, Puqing Jiang
Materials Science
Kinetic Arrest of a First Order Phase Transition
Sindhunil Barman Roy
We report a phenomenological theory for the kinetic arrest (KA) of a first-order phase transition, taking the Mott metal-
insulator transition in $V_2O_3$ as a test case. By defining a order parameter $\phi$ related to the monoclinic distortion of the high temperature metallic and mapping its Time-Dependent Ginzburg-Landau (TDGL) dynamics onto a disorder-influenced Imry-Wortis landscape, we derive a universal transcendental condition for the mechanism of the kinetic arrest. We demonstrate that epitaxial substrate-induced clamping in (001)-oriented $V_2O_3$ thin films elevates the elastic activation barriers, trapping the high-
symmetry corundum phase down to 4.2~K. This structural suppression of the insulating state robustly explains the observed hysteretic $V$-$I$ switching a hallmark of memristive behaviour. Our work identifies a "Mott-Glass" as a structurally arrested non-
equilibrium state in the strained thin-film of V$_2$O$_3$. Our work provides a predictive framework for engineering strain-tuned neuromorphic synapses.
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Materials Science
Depth-Resolved Thermal Conductivity of HFCVD Diamond Films via Square-Pulsed Thermometry
Kexin Zhang, Xiaosong Han, Ershuai Yin et al. (+3 more)
The integration of high-thermal-conductivity diamond films onto silicon carbide (SiC) substrates offers a promising pathway for thermal management in high-power electronic devices. Here, we investigate the depth-dependent thermal conductivity of a ~5 {\mu}m-thick diamond film grown on SiC by hot-filament chemical vapor deposition (HFCVD) using square-pulsed source (SPS) thermometry. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) reveal pronounced grain coarsening from the nucleation interface to the film surface. By combining frequency-dependent thermal penetration with a depth-resolved thermal transport model, we quantitatively reconstruct the thermal conductivity profile. The thermal conductivity increases sharply from ~60 W m^(-1) K^(-1) near the nucleation region to ~200 W m^(-1) K^(-1) at the surface, directly reflecting the underlying microstructural
evolution. These results provide a physically grounded understanding of graded heat transport in HFCVD diamond and offer practical guidance for engineering diamond-based thermal management layers for next-generation power devices.
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All authors Kexin Zhang, Xiaosong Han, Ershuai Yin, Xin Qian, Junjun Wei, Puqing Jiang
Mesoscale and Nanoscale Physics
Gate-Reconfigurable Single- and Double-Dot Transport in Trilayer MoSe2
Seungwoo Lee, Minjun Park, Yunsang Noh et al. (+8 more)
We report gate-controlled
quantum-dot transport in a trilayer MoSe2 device that combines a graphite back gate beneath the active region, a separate global gate for conductive access regions, and local top finger gates. In the low-backgate regime, bias spectroscopy shows regular Coulomb-blockade diamonds characteristic of single-dot transport. As backgate is increased, additional low-bias structure develops beyond a simple single-dot pattern, indicating that the electrostatic landscape is reshaped and that a second dot becomes active in transport. In the higher-backgate regime, plunger-gate tuning and two-gate measurements establish a gate-reconfigurable double-dot configuration with two non-equivalent dots whose relative
alignment and interdot coupling evolve with gate voltage. These results indicate that trilayer MoSe2 supports electrically reconfigurable single- and double-dot transport in the present device architecture.
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All authors Seungwoo Lee, Minjun Park, Yunsang Noh, Sung Jin An, Soyun Kim, Minseo Cho, Dohun Kim, Takashi Taniguchi, Kenji Watanabe, Minkyung Jung, Youngwook Kim
Strongly Correlated Electrons
Directional selection of field-induced phases by weak anisotropy in triangular-lattice K$_2$Mn(SeO$_3$)$_2$
Bin Wang, Yantao Cao, Andi Liu et al. (+15 more)
Triangular-
lattice systems host a variety of ground states, ranging from
quantum spin liquids to magnetically ordered phases, the latter of which can exhibit a sequence of
magnetic phase transitions under applied
magnetic fields. Here, we report
magnetic and thermodynamic measurements, combined with powder and single-
crystal neutron diffraction, on a high-
spin, nearly isotropic Mn$^{2+}$ triangular-
lattice system K$_2$Mn(SeO$_3$)$_2$. The compound undergoes long-range
magnetic ordering below $T_\mathrm{N} \sim 4$~K in zero field. Contrary to expectations for an ideal Heisenberg system, the compound adopts an up-down-zero (UD0)
magnetic structure down to the lowest temperature (0.05 K), rather than the commonly expected Y-type structure. This UD0 state is, however, highly sensitive to external
magnetic fields. For fields applied along the $c$ axis, it is readily destabilized and replaced by the Y-type structure, followed by an up-up-down (UUD) phase corresponding to the 1/3 magnetization plateau. In contrast, when the field is applied within the triangular plane, the system evolves into a canted Y state at a higher critical field. These results reveal that weak anisotropy, though small in magnitude, exerts a strongly orientation-dependent influence, playing a key role in selecting the field-induced phases in this frustrated magnet.
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All authors Bin Wang, Yantao Cao, Andi Liu, Guoliang Wu, Jin Zhou, Xiaobai Ma, Wenyun Yang, Takashi Ohhara, Akiko Nakao, Koji Munakata, Bing Shen, Zhendong Fu, Zhaoming Tian, Qian Tao, Zhu-an Xu, Wei Li, Jinkui Zhao, Hanjie Guo
Quantum Gases
Explicit proof of Anderson's orthogonality catastrophe for the one-dimensional Fermi polaron with attractive interaction
Giuliano Orso
We provide a fully analytical derivation of Anderson's orthogonality catastrophe for the one dimensional
Fermi polaron integrable model, describing a system of $N$
spin-up
fermions, with fixed density $n=N/L$, interacting with a single
spin-down
fermion via an attractive contact potential. The proof combines the determinant representations of the norm of the many-body wave function and of its scalar product with the noninteracting ground state, obtained from the Bethe ansatz solution, with the special properties of Cauchy
matrices. We derive the leading asymptotics of the two determinants in the thermodynamic limit and show that the quasi-particle residue $Z$ decays algebraically, $Z=W N^{-\theta}$. We confirm that the Anderson exponent $\theta$ is equal to $2\delta_F^2/\pi^2$, where $\delta_F$ is the Bethe-ansatz phase shift at the
Fermi edge. We also derive the asymptotic behavior of the prefactor $W$ at strong coupling and compare it against exact numerics.
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Disordered Systems and Neural Networks
Mobility-edge-embedded Hofstadter butterfly from a tilt-induced quasiperiodic potential
Sanghoon Lee and Kyoung-Min Kim
The Hofstadter butterfly (HB) and mobility edges (MEs) are hallmark phenomena of quasiperiodic systems, yet their interplay remains elusive. Here, we demonstrate their coexistence within a tilt-induced quasiperiodic potential on a square
lattice, giving rise to a “mobility-edge-embedded Hofstadter butterfly” (MEE-HB). This potential is generated by aligning a periodic potential at an angle relative to the
lattice axes – a configuration readily accessible in optical
lattice experiments. Using a tight-binding model, we show that the MEE-HB manifests as a fractal energy splitting pattern hosting MEs that separate extended and localized states. Our Harper-like equation shows that the fractal pattern originates from one-dimensional quasiperiodic potentials, while MEs stem from effective long-range hopping. Notably, the MEE-HB exhibits a fractal dimension of \(0.8\)–\(1.0\), significantly exceeding the \(0.4\)–\(0.6\) range of the standard butterfly, indicating a denser spectrum. Our findings establish tilt-induced potentials as a versatile platform for exploring the interplay between fractal structures and localization.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Many-body localization
Jakub Zakrzewski
We present an introductory review of nonergodic dynamics in interacting many-body
quantum systems, focusing on the phenomenon of many-body localization (MBL). We describe aspects of MBL and summarize the evidence for a crossover from the ergodic to the MBL regime in finite systems, using the paradigmatic XXZ model as an example. We then broaden the scope to other models to illustrate the generality of the phenomenon. We briefly touch on the largely unexplored relation between MBL and
quantum computing.
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Materials Science
Enhancing Laser Surface Texturing through Advanced Machine Learning Techniques
Christoph Zwahr, Frederic Schell, Tobias Steege et al. (+1 more)
Laser material processing has emerged as a versatile and indispensable tool in various industries, including manufacturing, healthcare, and materials science. However, the interaction of a
lasers with surfaces is highly dependent on a large number of factors, including properties of the
laser source such as pulse duration, wavelength and pulse form, as well as properties of the material such as surface roughness, heat capacity and thermal conductivity. Therefore, the optimization of
laser texturing processes in regards to specific target geometries while maintaining texture quality and process efficiency is a time consuming task that requires experienced operators with expert knowledge of the process and its components. The complex and nonlinear relationships between the various process,
laser and material parameters and the resulting surface topography or functionality are challenging to model analytically. Therefore, the fabrication of large numbers of different parameter variations are typically required to enable empirical modeling and process optimization. Machine learning offers a promising approach to overcoming these challenges, particularly when the interrelations between process parameters are not well understood. It enables effective process optimization, surface property prediction, and automated monitoring-tasks that previously required expert knowledge. This chapter demonstrates the application of machine learning to
Laser Surface Texturing techniques. Using
algorithms such as neural networks and random forests, surface roughness can be predicted based on
laser parameters and material data. This facilitates faster process optimization, reduces experimental effort, and enables predictive visualization - all while maintaining high accuracy.
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All authors Christoph Zwahr, Frederic Schell, Tobias Steege, Andrés Fabián Lasagni
Other Condensed Matter · Cross-listed from quant-ph
Dynamical $\mathbb{Z}_{2}$ Skin Channels and Effective Loschmidt Cusps
Yongxu Fu
We analytically describe the dynamically separated $\mathbb{Z}_{2}$ skin channels (wavepacket evolutions) under periodic boundary condition (PBC) in non-Hermitian systems with anomalous time-reversal
symmetry (ATRS), by combining the semiclassical worldline perspective with an enhanced understanding of skin effects. These channels, tied to the initial state and relevant
symmetries, exhibit individually exponential-dominated time
evolution in momentum space, where their amplitude maxima evolve toward the dominant momenta. In real space, their center of masses (COMs) circulate around the one-dimensional (1D) chain, tracing semiclassical worldlines. Such circulations imply
quantum revivals and effective Loschmidt cusps (LCs), with the latter showing scale-dependent behavior, a feature distinct from conventional dynamical
quantum phase transitions. This work extends our previous findings on worldline windings and the winding-control mechanism to the $\mathbb{Z}_{2}$ skin effects, confirming that the core physics is shared with the ordinary skin effect.
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Quantum Gases · Cross-listed from physics.atom-ph
Experimental Determination of the $D1$ Magic Wavelength for $^{40}$K
Guy Hay Kalifa, Dor Kopelevitch, Amir Stern et al. (+1 more)
Neutral-atom arrays offer a promising path for
quantum simulation, yet the potential of fermionic $^{40}$K remains largely constrained by state-dependent light shifts that degrade cooling and detection fidelities. This problem can be resolved by working at a magic wavelength, where the differential light shift vanishes. We report the first experimental determination of the magic wavelength for the D1 transition in fermionic $^{40}$K at 1227.54(4) nm. Using in-trap loss spectroscopy in a wavelength-tunable optical tweezer, we map the differential AC Stark shift across a range of trapping powers and wavelengths. By converting these shifts to differential scalar polarizabilities, we find excellent agreement with relativistic all-order calculations.
Benchmark measurements at 1064.49 nm further quantify the intensity-sampling systematics inherent to standard trapping wavelengths, contrasting with the “mechanically clean” environment provided by the magic condition. Our results provide an important step toward high-fidelity in-trap D1 cooling, fluorescence imaging, and light-assisted loading, establishing a robust path toward scaling fermionic neutral-atom arrays for
quantum information science.
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All authors Guy Hay Kalifa, Dor Kopelevitch, Amir Stern, Yoav Sagi
Statistical Mechanics
Generalized BChS Model with Group Interactions: Shift in the Critical Point and Mean-Field Ising Universality
Amit Pradhan
We introduce a generalized version of the Biswas-Chatterjee-Sen (BChS) model \cite{Biswas} with group interactions of size $q$, extending the original pairwise interaction dynamics. Within a mean-field framework, we derive an exact expression for the critical noise $p_c(q)$, showing that it increases monotonically with $q$ and approaches $1/2$ in the large-$q$ limit, consistent with a Gaussian approximation. Despite this shift in the phase boundary, the critical behavior remains unchanged across all $q$: the order parameter scales as $(p_c(q)-p)^{1/2}$, and the relaxation timescale diverges as $|p-p_c(q)|^{-1}$, identical to the original BChS model \cite{Biswas}. Finite-size scaling of the Binder cumulant, order parameter, and its fluctuations confirm that the system belongs to the mean-field Ising universality class for all $q$. Our results demonstrate that higher-order interactions modify the location of the transition without altering its universality class.
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Strongly Correlated Electrons · Cross-listed from hep-lat
Correctness criteria for complex Langevin
Michael Mandl
The complex Langevin approach is a promising method for the numerical treatment of systems with a sign problem, for which conventional
lattice field theory techniques based on importance sampling cannot be applied. However, complex Langevin dynamics may fail to converge in some cases and converge to a wrong limit in others, motivating the development of various diagnostic tools over the years to assess the correctness of given simulation results. This work aims at providing a systematic comparison between the most prominent such correctness criteria. In particular, the main goal is to contrast their applicability, ease of use, and - most importantly - their predictive power. To this end, four simple but nontrivial models are considered and the criteria applied to each of them. It is found that no single correctness criterion is entirely foolproof on its own and that it is advisable in practice to employ multiple different criteria in combination. These conclusions are expected to carry over to more realistic theories as well.
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Superconductivity
Kinetic instability and superconductivity in Li$_2$AuH$_6$ and Li$_2$AgH$_6$ at ambient pressure
Yucheng Ding, Haoran Chen and Junren Shi
Li$_2$AuH$_6$ and Li$_2$AgH$_6$ have been proposed as promising candidates for high-temperature
superconductors under ambient pressure. While previous studies confirm the dynamic stability of these two thermodynamically unstable systems, their kinetic stability against
quantum and thermal fluctuations remains to be verified. In this work, we use path integral molecular dynamics simulations to examine the kinetic stability of Li$_2$AuH$_6$ and Li$_2$AgH$_6$ under ambient pressure. We find both compounds are kinetically unstable. Li$_2$AgH$_6$ undergoes
lattice collapse, whereas Li$_2$AuH$_6$ retains a stable fluorite-type Li-Au sublattice, but hydrogen atoms partially dimerize into molecules and diffuse within the host
lattice. Using the
stochastic path-integral approach, which is a nonperturbative approach applicable to systems with diffusive atoms, we investigate the superconductivity of Li$_2$AuH$_6$ in this state. We predict a superconducting transition temperature of 22 K, well below earlier predictions, due to the low density of states at the
Fermi level caused by the collapse of hydrogen sublattice and hydrogen dimerization.
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Mesoscale and Nanoscale Physics
A CMOS-compatible, scalable and compact magnetoelectric spin-torque microwave detector
Shuhui Liu, Riccardo Tomasello, Bin Fang et al. (+10 more)
The development of compact and highly sensitive microwave detectors compatible with complementary-metal-
oxide-
semiconductor (CMOS) processes is an active research area but remains a major challenge in microwave technology.
Spin-torque diodes (STDs) are emerging nanoscale spintronic devices capable of surpassing the theoretical thermodynamic sensitivity limits of Schottky diodes. However, their practical use in compact systems is limited by the need of external
antennas or probes. Here, we demonstrate a magnetoelectric (ME)
spin-torque microwave detector that monolithically integrates an ME
antenna with a
magnetic tunnel junction (MTJ). The device directly converts wireless electromagnetic signals into a DC output at sub-microwatt power levels, achieving a sensitivity greater than 90 kV/W, a noise equivalent power of 3 pW*Hz^-0.5, and a compact footprint of 0.4 mm^2. This performance is due to the nonlinear coupling between incoherent magnetization dynamics, driven by a DC current in the MTJ, and the combined effects of the microwave voltage and strain generated by the ME
antenna under incident electromagnetic waves. We further show that this design is scalable, enabling the co-integration of an ME
antenna with an array of MTJs. A detector incorporating four MTJs, for example, exhibits a sensitivity exceeding 400 kV/W. This work paves the way for a new generation of highly sensitive, compact and scalable microwave detectors that combine ME
antennas and spintronic diodes.
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All authors Shuhui Liu, Riccardo Tomasello, Bin Fang, Aitian Chen, Like Zhang, Zhenhao Liu, Rui Hu, Wenkui Lin, Mario Carpentieri, Baoshun Zhang, Xixiang Zhang, Giovanni Finocchio, Zhongming Zeng
Strongly Correlated Electrons
Large spontaneous Hall effect arising from collinear antiferromagnetism in Ce$_2$PtGe$_6$
Hayata Matsuda, Ruo Hibino, Chihiro Tabata et al. (+9 more)
The spontaneous
Hall effect, corresponding to a zero-field anomalous
Hall effect (AHE), is induced by
symmetry breaking associated with ferromagnetism. Studies in recent years, however, have revealed that
antiferromagnetic (AFM) states characterized by
magnetic point groups that allow ferromagnetism can also break the relevant
symmetries and induce AHE without a large net magnetization. Here, we report that the AFM system Ce$_2$PtGe$_6$ exhibits a pronounced spontaneous
Hall effect. Single-
crystal neutron scattering experiments demonstrate that Ce$_2$PtGe$_6$ exhibits a collinear AFM structure with a propagation vector $q=0$. The small net magnetization of $\sim 10^{-3}$ $\mu_B$/Ce indicates that the observed AHE arises from
symmetry breaking inherent to its AFM structure. The anomalous
Hall conductivity (AHC) reaches $300$ $\Omega^{-1}$cm$^{-1}$, which exceeds the intrinsic AHC of related compounds such as Ce$_2$CuGe$_6$ and Ce$_2$PdGe$_6$. This large AHC, most likely attributed to the large
spin-orbit coupling of the Pt atoms, provides a platform for understanding the interplay between the Berry
curvatures and localized $f$-moments with an AFM configuration.
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All authors Hayata Matsuda, Ruo Hibino, Chihiro Tabata, Koji Kaneko, Nonoka Higa, Takahiro Onimaru, Hiroto Tanaka, Hideki Tou, Hitoshi Sugawara, Junichi Hayashi, Keiki Takeda, Hisashi Kotegawa
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Noise-Enhanced Self-Healing Dynamics in Non-Hermitian Systems
Wuping Yang and H. Huang
Self-healing is the ability of a wave packet to spontaneously restore its spatial profile after scattering. As an emergent feature of non-
unitary dynamics, it has attracted significant interest in non-Hermitian physics. Here, we systematically investigate how
stochastic noise influences edge self-healing. Counterintuitively, we find that noise can constructively enhance this dynamical process. Weak noise prolongs the self-healing window by aligning the finite-time Lyapunov exponent of the reference state with the maximum imaginary part of the energy spectrum. Remarkably, strong noise universally stabilizes asymptotic profile recovery across the entire spectrum by inducing an effective non-
unitary drift-
diffusion dynamics. We analytically elucidate these distinct mechanisms using a general finite-time Lyapunov exponent analysis, complemented by a dedicated perturbation theory for the strong-noise regime. Our results provide concrete guidance for realizing robust non-Hermitian dynamics in realistic noisy environments.
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Statistical Mechanics · Cross-listed from stat.ML
Information-Geometric Decomposition of Generalization Error in Unsupervised Learning
Gilhan Kim
We decompose the Kullback–Leibler generalization error (GE) – the expected KL divergence from the data distribution to the trained model – of unsupervised learning into three non-negative components: model error, data bias, and variance. The decomposition is exact for any e-flat model class and follows from two identities of information geometry: the generalized Pythagorean
theorem and a dual e-mixture variance identity. As an analytically tractable demonstration, we apply the framework to $\epsilon$-PCA, a regularized principal component analysis in which the empirical covariance is truncated at rank $N_K$ and discarded directions are pinned at a fixed noise floor $\epsilon$. Although rank-constrained $\epsilon$-PCA is not itself e-flat, it admits a technical reformulation with the same total GE on isotropic Gaussian data, under which each component of the decomposition takes closed form. The optimal rank emerges as the cutoff $\lambda_{\mathrm{cut}}^{*} = \epsilon$ – the model retains exactly those empirical
eigenvalues exceeding the noise floor – with the cutoff reflecting a marginal-rate balance between model-error gain and data-bias cost. A boundary comparison further yields a three-regime phase diagram – retain-all, interior, and collapse – separated by the lower Marchenko–Pastur edge and an analytically computable collapse threshold $\epsilon_{*}(\alpha)$, where $\alpha$ is the dimension-to-sample-size ratio. All claims are verified numerically.
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Superconductivity
Chu-Tian Gao, Chen Lu, Yu-Bo Liu et al. (+2 more)
Unconventional superconductivity (SC) characterized by multi-
fermion orderings has attracted substantial
attention. However, previous studies have largely focused on 2D systems or 3D systems with effective 2D
symmetries. Here, we investigate the vestigial phases arising from thermal fluctuations of
chiral SC in 3D systems governed by the cubic $O_h$ point group. By constructing low-energy effective
Hamiltonians via Ginzburg-Landau analysis and conducting Monte Carlo simulations, we systematically investigate the phase fluctuations of
chiral orders within the $E_g$ and $T_{2g}/T_{1u}$ irreducible representations (IRRPs). We identify a phase diagram
topology different from 2D counterparts, where the multi-phase intersection manifests as a tetracritical point rather than the triple point typically found in 2D systems. We elucidate the
evolution of these phases under thermal fluctuations. Our findings reveal that for both $E_g$ and $T_{2g}/T_{1u}$ IRRPs, the primary
chiral orders could melt into a
chiral metallic phase across specific parameter regimes. Moreover, for the $E_g$ IRRP, phase fluctuation could also induce a charge-$4e$ phase under certain regime, while for the $T_{2g}$ and $T_{1u}$ IRRPs, it leads to a higher-order charge-$6e$ SC state. Our work paves the way for exploring exotic vestigial orders driven by non-trivial 3D crystalline
symmetries.
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All authors Chu-Tian Gao, Chen Lu, Yu-Bo Liu, Zhiming Pan, Fan Yang
Other Condensed Matter
Momentum-dependent charge-density-wave gap formation in ZrTe_{2.98}Se_{0.02}
Iori Ishiguro, Hayate Kunitsu, Natsuki Mitsuishi et al. (+5 more)
We investigated the energy gap formation across the charge density wave (CDW) transition inof ZrTe_{2.98}Se_{0.02}. By employing a
laser photoemission microscopy, we clearly resolved one elliptical
Fermi surface (FS) around the Brillouin zone (BZ) center, and two quasi-one-dimensional FSs along the BZ boundary. We further mapped the intensity difference between the FSs below and above the CDW transition temperature. We found that the energy CDW gap formation is limited to the momentum region 0.25 Å^{-1} < ky < 0.8 Å^{-1} along \bar{B}-\bar{D} line, which coincides with the location of one of the quasi-one-dimensional FSs. Characteristic momentum dependence in the energy CDW gap suggests the importance of both FS nesting and band-dependent electron-
phonon coupling for understanding the CDW state in ZrTe_{3} system.
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All authors Iori Ishiguro, Hayate Kunitsu, Natsuki Mitsuishi, Shunsuke Tsuda, Koichiro Yaji, Yoichi Yamakawa, Hiroshi Kontani, Takahiro Shimojima
Statistical Mechanics · Cross-listed from quant-ph
The Quantum Kicked Rotor: A Paradigm of Quantum Chaos. Foundational aspects and new perspectives
Giuliano Benenti, Giulio Casati, Jiangbin Gong et al. (+1 more)
The kicked rotor provides a simple yet powerful model for introducing many of the central concepts of classical and
quantum chaos. Despite its apparent simplicity, it exhibits rich dynamical behavior and has found applications across a wide range of fields, including atomic and optical physics, condensed matter physics, and emerging
quantum technologies. This chapter begins by exploring foundational ideas using the kicked rotor as a unifying framework. We first discuss the transition from regular to chaotic motion in the classical system, and then introduce key
quantum phenomena such as dynamical localization and
quantum resonances. Special
attention is devoted to the emergence of characteristic time scales and their role in the
quantum-classical correspondence. To make these ideas more concrete, we also provide a brief overview of experimental realizations of the kicked rotor and its variants, illustrating how theoretical concepts are implemented in practice. In the second part of the chapter, we guide the reader toward more recent and advanced developments. Topics include near-resonant dynamics, topological features of kicked systems, the emergence of
quantum dynamical phases inferred from classical transport properties, and extensions to non-Hermitian physics. We conclude with a discussion of open problems and future perspectives, outlining directions in which the kicked rotor continues to offer valuable insights.
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All authors Giuliano Benenti, Giulio Casati, Jiangbin Gong, Zhixing Zou
Superconductivity
Nanoscale electrothermal-switch superconducting diode for electrically programmable superconducting circuits
Tianyu Li, Jiong Li, Chong Li et al. (+13 more)
Superconducting diodes enable dissipationless directional transport, yet achieving electrical tunability and scalability remains a major challenge for
circuit-level integration. Here, we demonstrate an electrothermal-switch superconducting diode in which a gate-controlled nanoscale hotspot dynamically breaks inversion
symmetry in a superconducting nanowire. This mechanism gives rise to two coexisting nonreciprocal transport regimes-one associated with a nonreciprocal superconducting-to-normal transition and the other with ratchet-like
vortex dynamics-both originating from the same electrothermal-switch process. The diode exhibits efficiencies up to 42% and 60% for the two regimes, respectively, and can be electrically switched on, off, or reversed in polarity in situ by applying a small gate current. These capabilities enable programmable superconducting
circuits that realize electrically reconfigurable full-wave and half-wave rectification. The lithography-compatible design, high performance, and gate-controlled functionality establish a scalable platform for programmable superconducting electronics and hybrid
quantum systems.
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All authors Tianyu Li, Jiong Li, Chong Li, Peiyuan Huang, Nuo-Zhou Yang, Wuyue Xu, Wen-Cheng Yue, Yang-Yang Lyu, Yihuang Xiong, Xuecou Tu, Tao Tao, Xiaoqing Jia, Qing-Hu Chen, Huabing Wang, Peiheng Wu, Yong-Lei Wang
Mesoscale and Nanoscale Physics
Giant and Helical Exciton Dipole from Berry Curvature in Flat Chern Bands
Kaijie Yang, Huiyuan Zheng, Xiaodong Xu et al. (+2 more)
We show that
excitons forming between moiré flat Chern bands possess a substantial electric dipole moment comparable to the moiré
lattice parameter times the elementary charge ($\sim10^2$ Debye). At a hole filling factor of one in twisted MoTe$_2$, the dipole moment of the lowest-energy
exciton branch develops in-plane helical texture in momentum space from the intrinsic Berry
curvature of electron and hole. By solving the Bethe-Salpeter equations, we demonstrate that an out-of-plane displacement field induces a Frenkel-to-Wannier
exciton transition, accompanied by a reversal of the dipole texture helicity. The resulting attractive
exciton dipole-dipole interactions lead to quadrupolar biexcitons that can be probed via two-
photon spectroscopy. Our findings establish band
topology as a tunable knob to engineer
exciton dipole moments and pave the way to manipulate many-body interactions in the terahertz regime.
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All authors Kaijie Yang, Huiyuan Zheng, Xiaodong Xu, Di Xiao, Ting Cao
Mesoscale and Nanoscale Physics
Interplay of strain-induced axial gauge fields and intrinsic band-topology in the magnetoelectric conductivity of gapped nodal rings
Firdous Haidar, Muhammed Jaffar A. and Ipsita Mandal
We compute the magnetoelectric conductivity of a semimetal hosting an ideal gapped nodal ring (GNR) in three distinct planar-
Hall configurations, in the simultaneous presence of an external electric field $\boldsymbol{E}$, a
magnetic field $\boldsymbol{B}$, and a strain-induced axial pseudomagnetic field $\boldsymbol{B}_5$. The latter arises from a nonuniform
lattice deformation and couples to antipodal points on the toroidal
Fermi surface with opposite signs, reflecting its
chiral nature. Extending our earlier analysis to include $\boldsymbol{B}_5$, we demonstrate how its
vortex-like field lines — co-aligned with the Berry
curvature (BC) and orbital
magnetic moment (OMM) — imprint qualitatively distinct signatures on the conductivity tensor. In particular, this
alignment causes the dot product of $\boldsymbol{B}_5$ with the BC or OMM-induced quantities to be angle-independent on the
Fermi surface, generating a nonvanishing integral linear-in-$B_5$, which is not possible for isotropic nodal points harbouring BC-monopoles. We show that a part of the planar-
Hall conductivity in the first set-up remains completely immune to strain, providing a strain-insensitive internal reference for topological transport. Our explicit analytical expressions offer concrete and experimentally-testable predictions for identifying strain-induced signatures in transport measurements on GNR materials.
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Mesoscale and Nanoscale Physics
Ian Babich, Timofey M. Savilov, Natalia A. Mamchik et al. (+14 more)
The advent of van der Waals (vdW)
heterostructures has enabled formation of bespoke materials with atomic precision, where numerous
quantum and topological phenomena have already been discovered. This atomic-layer tunability, however, comes at a cost: individual 2D layers must be picked up, moved, and placed in a deterministic manner while keeping their interfaces atomically clean. Recent advances in machine learning and robotics place even stronger emphasis on the deterministic aspect of vdW assembly. Current
polymer-based transfer methods satisfy neither the determinism nor cleanliness requirements. To this end, solutions are needed where adhesion can be dynamically and deterministically controlled without leaving organic contamination. Here, we present a
polymer free transfer technique employing thin muscovite (mica)
crystals. Temperature control over mica adhesion enables deterministic pick-up, stacking, and release of 2D materials, while their crystalline, inorganic nature ensures pristine interfaces and suppresses strain. Fully compatible with existing fabrication workflows, this approach enables the assembly of demanding vdW
heterostructures, including those with exposed conductive layers, moiré superlattices and suspended membranes. Our method represents a promising strategy for vdW
heterostructure fabrication toward its automatization.
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All authors Ian Babich, Timofey M. Savilov, Natalia A. Mamchik, Kristina Vaklinova, Nansi Zhou, Denis S. Baranov, Dmitrii A. Litvinov, Virgil Gavriliuc, Yue Yuan, Amoz Chua, Kenji Watanabe, Takashi Taniguchi, Mario Lanza, Maciej Koperski, Kostya S. Novoselov, Alexey I. Berdyugin, Makars Šiškins
Strongly Correlated Electrons
Orbital-selective correlations and angular momentum coupling in heavy actinides Am, Cm, Bk, and Cf under pressure: A many-body perspective
Haiyan Lu
We systematically investigate the electronic structures of americium (Am), curium (Cm), berkelium (Bk), and californium (Cf) in both the ambient-pressure double hexagonal close-packed (dhcp) and high-pressure face-centered cubic (fcc) phases, using density functional theory combined with embedded dynamical mean-field approach. Our results reveal that Am exhibits moderate correlation strength and localized 5f states dominated by jj angular momentum coupling scheme. In Cm and Bk, strong electron correlations drive the system into a localized regime, characterized by Hubbard band formation, large effective electron masses, and non-
Fermi liquid behavior. Their
magnetic ground states are governed by exchange interactions within an intermediate coupling scheme that shifts toward LS coupling. Remarkably, Cf reenters a jj coupling regime while exhibiting the strongest orbital-selective correlations among the series. Atomic eigenstate probabilities show moderate configurational mixing in Am, whereas Cm, Bk, and Cf maintain nearly fixed trivalent configurations, indicating localized 5f states. Compared with the dhcp phase, the fcc structure generally enhances correlation effects, as evidenced by wider Hubbard bandgaps and increased valence state fluctuation in Am. Analyses of kinetic energy, potential energy,
spin susceptibility, and charge susceptibility further corroborate the progressive localization of 5f electrons and the emergence of orbital-selective correlations from Am to Cf. This work establishes a unified picture of 5f electron
evolution across the Am-Cf series, elucidating the interplay between
spin-orbit coupling, electron correlation, and
crystal structure in heavy actinides and offering insights into their behavior under high pressure.
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Statistical Mechanics
Steady-State Equilibrium and Nonequilibrium Noisy Network Dynamics
Pik-Yin Lai
The fluctuating dynamics of a network about its stable, noise-free steady state are theoretically investigated. Various causes of non-
equilibrium dynamics are identified in terms of the properties and
symmetry of the network connections and the noise covariance
matrices. Several equivalent conditions are derived for the dynamics of the noisy network at
equilibrium. In particular, non-
equilibrium steady state (NESS) dynamics are analyzed in terms of the steady-state probability current and the drift velocity relative to the effective potential surface. Conventional physical Brownian dynamics for overdamped fluctuating dynamics is analyzed from the perspective of the linearized fluctuating noisy network dynamics. Connection with the network reconstruction from time-series data is discussed. It is demonstrated that the overdamped Brownian dynamics in the physical system is a special case of the general noisy directed network in a NESS. Furthermore, a general fluctuation-dissipation relation is derived for the general non-
equilibrium noisy network dynamics. These theoretical results are verified by numerical simulations.
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