Papers

We construct a many-body model Hamiltonian to capture how phonons renormalize exciton binding as a function of temperature. By using the GW approximation and density functional perturbation theory, we are able to parameterize this Hamiltonian completely from first principles. To capture static quasiparticle properties non-perturbatively, we evolve this Hamiltonian in imaginary time with path integral Monte Carlo using an influence functional based approach. For a class of Wannier-Mott type excitons, our binding energies are in quantitative agreement with experiment. We find that in addition to long-range dipolar interactions from longitudinal optical modes, short-ranged deformation potentials from acoustic modes and transverse optical modes can significantly renormalize electron and hole polaron binding energies at elevated temperature. However, exciton binding energies are only appreciably renormalized by coupling to optical phonons.

Based on detailed first-principles calculations, we investigate the tetragonal-to-hexagonal phase transition in Fe-doped BaTiO$_3$. Free energy calculations confirm a crossover from the tetragonal to hexagonal phases at 2.7–6% Fe on cooling from the sintering temperature, in agreement with experimental observations, where comparative calculations show that neither CaTiO$_3$ nor SrTiO$_3$ exhibits similar behavior under equivalent substitution. Furthermore, three possible mechanisms are quantified: oxygen vacancies shift the crossover concentration from 2.7–6% to 1.1–4.7%, Jahn-Teller distortions are confined to the tetragonal phase, both favoring tetragonal-to-hexagonal phase transitions; whereas the tolerance factor is reduced in comparison with that of pristine BaTiO$_3$ for reasonable Fe valence states, disfavoring the occurrence of the hexagonal phases. Detailed analysis on the electronic structure reveals that the charge redistribution induced by oxygen vacancy is strongly orbital dependent, the added charge entering the $d_{z^2}$ orbital.

We review recent theoretical and experimental developments in magnetic Weyl semimetals, focusing on the electromagnetic responses emerging from the interplay of their electronic band topology and magnetism. We begin by introducing the fundamental topological properties of the electrons in Weyl semimetals, and provide an overview of the characteristic phenomena arising from their band topology, such as the anomalous Hall effect and chiral magnetic effect. The materials exhibiting the magnetic Weyl semimetal state, with ferromagnetic ordering, antiferromagnetic ordering, etc., are listed. The possible mechanisms for their magnetism are discussed in connection with the Weyl electrons. Non-uniform magnetic textures and magnetization dynamics are expected to exhibit a topological interplay with the Weyl electrons, manifesting as spinmotive force and spin torques. We also review the magnetotransport phenomena such as domain wall magnetoresistance, studied by mesoscopic scale calculations. Finally, we mention the spin transport properties studied in magnetic Weyl semimetals. The topological nature of Weyl electrons reviewed here is important not only for fundamental physics, but also for the potential application to low-dissipative electronics and spintronics devices.

Classical thermodynamics contains familiar geometric relations associated with cyclic processes, most notably the identification of mechanical work with the area enclosed by a trajectory in the $(P,V)$ plane. We show that the area laws for work and reversible heat arise as projections of a single canonical two–form defined on the equilibrium thermodynamic manifold, providing a unified description of thermodynamic cycles in both the $(P,V)$ and $(T,S)$ representations. The same structure yields a direct link between cycle geometry and thermodynamic response: the work generated by infinitesimal cycles is set locally by the mixed curvature $U_{SV}$ of the equilibrium energy surface, which can be expressed in terms of measurable susceptibilities. This identifies thermodynamic work as a local geometric field over state space rather than solely a global property of cyclic processes. More broadly, the framework connects classical cycle geometry to stochastic thermodynamic trajectories, providing a geometric interpretation of nonequilibrium work relations such as the Jarzynski equality.

Simulations of electrochemical double layer capacitors based on porous carbon electrodes, energy storage systems which accumulate and release energy through reversible ion adsorption at electrode/electrolyte interfaces, are often performed at the microscopic scale, using molecular dynamics. Such simulations provide crucial information to understand the adsorption of ions and the effect of confinement on some electrochemical properties. However, their computational cost limits the size of the systems studied to a few nanometers and a few pores while experimental materials are highly heterogeneous with a distribution of particle and pore sizes. LPC3D is a software designed for mesoscopic simulations of porous carbon particles and carbon-based supercapacitors which allow for the inclusion of such heterogeneity. The code calculates quantities of adsorbed ions, diffusion coefficients and NMR spectra of ions / molecules adsorbed in porous carbon matrices. In this work, we report on a new implementation of LPC3D, written in Python using the PyStencils module which can generate optimized C++ and CUDA code. This implementation is parallel, can be run on CPU and GPU, and allows one to simulate systems going from a single carbon particle to a supercapacitor with hundreds of micrometers in length. Here, we apply the new implementation of LPC3D to the simulation of supercapacitors with porous carbon electrodes represented as monoliths or carbon films to investigate the influence of the microstructure on the resulting adsorption and spectroscopic properties.

We introduce Biphoton Entanglement Light Spectroscopy (BELS), a quantum spectroscopic technique that employs polarization entangled Bell pairs and two photon interference to probe material properties. In BELS, the measured signal arises not from single photon intensities but from changes in the joint polarization and path correlations of biphoton Bell pairs transmitted through or scattered by a sample and analyzed via cross channel coincidences. A key concept of BELS is the explicit mapping between Jones matrix operations and transformations within the Bell state manifold. Optical elements that are equivalent under classical polarization optics can produce qualitatively distinct signatures in the coincidence landscape when interrogated with entangled photons. We demonstrate that linear birefringence and Faraday rotation generate orthogonal admixtures of Bell states, yielding experimentally distinguishable coincidence channels within a single measurement. We measure birefringence in an anisotropic dielectric and Faraday rotation in $\text{Tb}_3\text{Ga}_5\text{O}_{12}$. By mapping the changes to the photonic entanglement, BELS establishes a new framework for future entanglement enhanced spectroscopy, a potentially powerful approach in characterizing quantum materials, nanophotonic devices, and light matter interactions perhaps eventually at a fundamentally quantum level.

Carbon-electrode-based PSC devices are stressed under 1 Sun equivalent illumination in a stability setup, and different scan-speed dependent current-voltage (J-V) curves are measured during aging. The collected data is used to estimate several physical parameters that contain information about charge transport and recombination using Machine Learning (ML), which allows for in situ tracking of possible signs of degradation. These results are compared to what can be classically interpreted by analysing changes in J-V curves, and the evolution of the predicted parameters is studied. The predictions are then used to simulate a digital twin of the measured devices, and their physical implications and the differences between measurements and devices are discussed.

Recent advances in on-surface chemistry, combined with scanning probe microscopy, have enabled the synthesis of correlated molecules on surfaces and the characterization of their chemical and electronic properties with unprecedented spatial resolution. Low-energy magnetic excitations of individual molecules are frequently investigated by scanning tunneling spectroscopy (STS) and often appear as symmetric step-like features in the differential conductance as a function of bias voltage. The interpretation of such steps is well established within cotunneling theory and effective model Hamiltonians (e.g., Hubbard- and spin-based models). Here, we extend the cotunneling formalism to general multireference systems. We show that multireference character, together with orbital-dependent and strongly asymmetric tip/substrate couplings, can produce pronounced asymmetric line shapes in inelastic STS. These results provide an alternative microscopic mechanism for the asymmetric peaks and dips near the Fermi level frequently observed in STS experiments.

With growing interest in structural chirality in periodic solids, it has been suggested that chirality might constitute a new ferroic order parameter. In this work, we demonstrate, by means of a formal group-theoretical proof and a systematic group-subgroup analysis, that achiral-to-chiral transitions that produce either member of an enantiomorphic pair cannot be driven by a Brillouin-zone-center ($\Gamma$-point) instability from a common achiral parent. We further substantiate this result by explicitly showing that none of the achiral parent space groups that admit symmetry-chiral phonon eigenvectors host them at the zone center. Given that a primary ferroic order parameter must, among other requirements, transform according to a zone-center irreducible representation, we conclude that phase transitions leading to enantiomorphic space groups cannot be classified as primary ferroic transitions. This predicts that any critical enhancement of fluctuations must occur at finite-$q$ rather than as a divergence of a uniform macroscopic susceptibility.

Sodium layered oxides often undergo phase transformations involving ordering or disordering of Na+ upon desodiation, i.e., when cycled as a battery electrode. Accurately characterizing these phases is crucial for understanding functional properties, such as chemical diffusivity. In this work, we reveal that Na+-vacancy (dis)ordering in a layered oxide is intrinsically coupled to symmetry-changing phase transformations of the host structure. We examine the low-symmetry orthorhombic unit cell of P2-NaxNi1/3Mn2/3O2 (NNM) using both neutron and X-ray diffraction. Specifically, special sodium stoichiometries (x = 2/3 and 1/2) exhibit concomitant Na+-vacancy ordering and an orthorhombic distortion from the parent hexagonal unit cell. We then demonstrate that electrochemical desodiation drives symmetry-changing transformations in NNM that are linked to Na+-vacancy (dis)ordering, with evidence of second-order behavior observed near x = 2/3. Variable-temperature synchrotron X-ray diffraction further clarifies the coupling between Na+-vacancy disordering and orthorhombic-to-hexagonal phase transitions in NNM. Surprisingly, the temperature-driven phase transitions at x = 2/3 and 1/2 differ in character, appearing second-order and first-order, respectively. Our analysis of the phase transitions in NNM has fundamental consequences for sodium chemical diffusivity in the vicinity of the ordered phases and leads to design principles for modifying phase transition behavior in the broader class of intercalation electrodes.

We investigate the microscopic properties of the kagome compound Cs$_2$Cu$_3$SnF$_{12}$ using $^{63,65}$Cu nuclear quadrupolar resonance (NQR). Analysis of the local hyperfine fields below the Néel temperature $T_N = 20$ K indicates a spin structure consistent with $P2_1/n$ symmetry of negative vector chirality. Measurements of the spin-lattice relaxation rate $T_1 ^{-1}$ reveal signatures of a gapless ground state and two-dimensional Berezinskii-Kosterlitz-Thouless (BKT)-type correlations above $T_N$, extending over a broad temperature range of approximately 130 K in zero magnetic field. Within the same temperature range, the observed increase in the NQR linewidth is consistent with short-range chiral order recently identified by neutron scattering. Our results establish Cs$_2$Cu$_3$SnF$_{12}$ as a unique quantum kagome system exhibiting BKT behavior.

We formulate a geometric framework for quasistatic thermodynamics in open quantum systems by parameterizing the dynamics on a control manifold. In the quasistatic limit, the system follows a manifold of stationary states, and the work performed over a cycle is given by the flux of a curvature two-form, $W \sim \int \Omega$, defined by the parametric response of the stationary state, establishing an open-system analog of classical thermodynamic area laws. \erbedit{For thermal stationary states at fixed temperature, the curvature vanishes, reflecting the integrability of the work one-form.} Beyond this limit, nonequilibrium stationary states can retain coherence in the energy representation; using a fixed-basis Lindblad model, we show that this coherence reshapes the curvature, making it anisotropic and sign-changing, so that work depends sensitively on the placement and orientation of the cycle. Quantum coherence, therefore, partitions the control manifold into regions of opposite curvature, producing geometric cancellation of work and allowing the net work over a cycle to be reduced or reversed despite dissipative dynamics. Thermodynamic work thus emerges as a curvature flux whose structure is set by thermodynamic response in classical systems and by basis misalignment between the Hamiltonian eigenbasis and the environment-selected pointer basis in open quantum systems.

Deterministic classical cellular automata can be in two phases, depending on how irreversible the dynamical rules are. In the strongly irreversible phase, trajectories with different initial conditions coalesce quickly, while in the weakly irreversible phase, trajectories with different initial conditions can remain different for a time exponential in the system volume. The transition between these phases is referred to as the damage-spreading transition (the "damaged" sites are those that differ between the trajectories). We develop a theory for this transition. In the simplest and most generic setting, the transition is known to be related to directed percolation, one of the best-studied nonequilibrium phase transitions. However, we show that full theory of the damage-spreading critical point is richer than directed percolation, and contains an infinite hierarchy of sectors of local observables. Directed percolation describes the first level of the hierarchy. The higher observables include "overlaps" for multiple trajectories, and may be labeled by set partitions. (These higher observables arise naturally if, for example, we consider decay of entropy under the irreversible dynamics.) The full hierarchy yields a hierarchy of nonequilibrium fixed points for reaction-diffusion-type processes, all of which contain directed percolation as a subsector, but which possess additional universal critical exponents. We analyze these higher fixed points using a field theory formulation and renormalization group arguments, and using simulations in 1+1 dimensions.

We study the simplest terms that need to be included in active field theories to couple them to external potentials. To do so, we consider active Brownian particles and implement a systematic perturbative expansion in the particle persistence time. The result is a non-trivial coupling between density and potential gradients, which accounts for the nonequilibrium features of active particles in the presence of an external potential, from boundary accumulation to far-field density modulation. We show how the method can be applied to particles interacting via pairwise forces and to spatial modulations of the propulsion speed.

We study magnetic materials whose low energy physics can be effectively described by a Dicke model, which we term Dicke materials. We show how a Dicke model emerges in such materials due to a coexistence of fast-dispersing and slow-dispersing spins, which are strongly coupled. Analogous to the paradigmatic Dicke model describing light-matter interactions, these materials also exhibit signatures of a superradiant phase transition. The ground state near the superradiant phase transition is expected to be squeezed, making Dicke materials a resource for quantum metrology and witnessing entanglement in solid-state systems. However, as an entanglement measure, squeezing can be sensitive to perturbations that are otherwise irrelevant for usual correlation functions and order parameters. Motivated by the prospect of observing squeezing in such Dicke materials, we study the robustness of ground state squeezing under ubiquitous imperfections such as finite temperature, disorder, and local interactions. Using analytical and numerical techniques, we show that the squeezing obtained is perturbatively stable against these imperfections and quantitatively evaluate regimes promising for experimental observation.

Several candidate reference phases have been proposed to discuss phase transitions and ferroelectricity in hafnia in recent years. Although these proposals comply with crystallographic requirements, a physically compelling rationale connecting parent and daughter phases is often lacking. This problem is aggravated by the absence of clearly dominant polarization switching pathways, making it difficult to formulate a robust physical criterion for identifying the relevant high-symmetry states. Here we use first-principles calculations to show that pressure provides a simple and robust criterion for establishing physically meaningful family relationships among many hafnia polymorphs, including the monoclinic ground state and the technologically relevant ferroelectric phase, and their respective parent structures. Our simulations also reveal several previously unreported phases, including higher-energy structures that act as common ancestors of the widely discussed cubic and orthorhombic reference phases.

Boundary perturbations are generally irrelevant for bulk properties in the thermodynamic limit, as they are edge-confined and subextensive. We show that this expectation breaks down in boundary-driven systems exhibiting the non-Hermitian skin effect, where arbitrarily weak boundary Floquet driving reconstructs bulk quasienergy spectra and dynamics. We develop a Floquet non-Bloch band theory that extends generalized Brillouin-zone methods to boundary-driven systems at arbitrary driving frequencies, overcoming the lack of a general framework beyond high-frequency approximations. With representative single- and two-band models, we demonstrate that the boundary driving frequency tunes non-Bloch parity-time symmetry breaking, while its amplitude acts as a finite-size control parameter. Our work establishes boundary Floquet control as a general route for manipulating bulk properties, opening a new avenue for dynamical engineering in driven open systems.

We study sum rules that control the Regge limit of one-dimensional conformal field theory (CFT) correlators and relate them to dual bulk scattering processes at high energies in $\mathrm{AdS}_2$. By imposing the condition that no scattering takes place in the bulk, these sum rules single out special solutions to crossing symmetry that describe long-range models, which can be understood as free fields in AdS with boundary interactions tuned to criticality. We test these sum rules perturbatively in several distinct theories, namely the 1d long-range versions of the Ising, $O(N)$ and Lee–Yang models, and find that they correctly predict the CFT data characterising these theories. Along the way we compute for the first time the leading contributions of quadruple-twist operators to the long range Ising correlator and analyse their role in the new sum rules. Finally, we explore the consequences of imposing these sum rules in a numerical bootstrap framework and find that they lead to substantial reductions in the allowed parameter space.

We study phases of itinerant anyons when hole-doping Laughlin-like states in fractional Chern insulators (FCIs). In light of the recent observation of time-reversal-broken superconductivity near FCIs in van der Waals materials, a theoretical understanding of doped fractional quantum Hall states on a lattice has been developed by Shi and Senthil [Phys. Rev. X 15, 031069], reviving old ideas about "anyon superconductivity". We test these ideas analytically within an effective parton mean-field theory and numerically with variational Monte Carlo, pointing out that the predicted state depends on whether the Laughlin order at $\nu=1/m$ is described by a U(1), or an SU(m) Chern-Simons field, the latter implying a symmetry between the m parton species. Our results demonstrate that the interplay between band Berry curvature and effective anyon dispersion has crucial implications for which anyonic phase is realized. In the experimentally relevant scenario of hole-doping the $\nu=1/3$ fermionic FCI, our results uncover a mechanism for the formation of an anyon superconducting state of half-integer central charge in the case when the energetically cheapest excitations are the fundamental 1/3 charge anyons, bypassing the need for these anyons to pair into charge-2/3 composites, which has generally been assumed in similar anyon superconductivity constructions.

Non-Hermitian evolution is mathematically invertible, yet finite dynamic range imposes a sharp operational limit on reversibility. We identify Precision-Induced Irreversibility (PIR): amplification, mode mixing (as warranted by non-normality), and a finite resolution floor – whether set by numerical precision, detector noise, or environmental fluctuations – conspire to produce a quantitative predictability horizon $T_{\mathrm{of}}$, beyond which distinct states collapse onto identical representations. Within the effective non-Hermitian description, the mechanism requires neither environmental decoherence nor nonlinear dynamics; remove any ingredient and reversibility can be restored. Echo-fidelity tests confirm this transition across arbitrary-precision arithmetic and hardware, revealing where formal invertibility and physical reversibility diverge.

We study the phase diagram of interacting spinless fermions on the honeycomb bilayer at charge neutrality using large-scale quantum Monte Carlo simulations. In the noninteracting limit, the low-energy spectrum features quadratically dispersing bands that touch at the corners of the hexagonal Brillouin zone. Weak to intermediate interactions induce a splitting of each of the quadratic band touching points into four Dirac points, located along high-symmetry directions of the reciprocal lattice. Strong interactions lead to the formation of a layer-polarized charge density wave, which spontaneously breaks the $\mathbb Z_2$ layer inversion symmetry and opens an insulating gap in the spectrum. We show that the semimetal-to-insulator quantum phase transition as a function of interaction is continuous and characterized by emergent relativistic symmetry. Our results for the values of the correlation-length exponent $\nu$, the order-parameter anomalous dimension $\eta_\phi$, and the fermion anomalous dimension $\eta_\psi$ agree with those of the theoretically predicted 2+1D Gross-Neveu-Ising universality class with eight two-component Dirac fermions within less than 5%\ deviation. We also determine the crossover scale as a function of interaction strength between the nonrelativistic semimetal state at high temperatures, characterized by dynamical critical exponent $z = 2$, and the Dirac semimetal state at intermediates temperatures, characterized by $z=1$. Further reducing the temperature below the crossover scale at a fixed value of the interaction strength above the quantum critical point results in a classical ordering transition in the 2D Ising universality class.

Sodium-ion batteries require anodes that combine high capacity, low operating voltage, fast Na-ion transport, and mechanical stability, which conventional anodes struggle to deliver. Here, we use the SpookyNet machine-learning force field (MLFF) together with all-electron density-functional theory calculations to characterize Na storage in aminobenzene-functionalized Janus graphene (Na$_x$AB) at room-temperature. Simulations across state of charge reveal a three-stage storage mechanism-site-specific adsorption at aminobenzene groups and Na$_n$@AB$_m$ structure formation, followed by interlayer gallery filling-contrasting the multi-stage pore-, graphite-interlayer-, and defect-controlled behavior in hard carbon. This leads to an OCV profile with an extended low-voltage plateau of 0.15 V vs. Na/Na$^{+}$, an estimated gravimetric capacity of $\sim$400 mAh g$^{-1}$, negligible volume change, and Na diffusivities of $\sim10^{-6}$ cm$^{2}$ s$^{-1}$, two to three orders of magnitude higher than in hard carbon. Our results establish Janus aminobenzene-graphene as a promising, structurally defined high-capacity Na-ion anode and illustrate the power of MLFF-based simulations for characterizing electrode materials.

Global entanglement in quantum many-body systems is inherently nonlocal, raising the question of whether it can be inferred from local observations. We investigate this problem in monitored quantum circuits, where projective measurements generate classical records distributed across spacetime. Using graph neural networks (GNNs), we represent individual quantum trajectories as directed spacetime graphs and reconstruct the half-chain entanglement entropy from local measurement data alone. Because information propagates through the network via local message passing, the architecture directly controls the spacetime region over which correlations can be aggregated. By systematically varying this accessible scale – through network depth and hierarchical spacetime coarse-graining – we probe how much measurement information is required to reconstruct global entanglement. We find that prediction accuracy improves as the accessible spacetime region grows and that results from different architectures collapse when expressed in terms of an effective spacetime scale combining depth and coarse-graining. These results demonstrate that the information required to reconstruct global entanglement is organized in spacetime scales and show that graph-based learning architectures provide a controlled operational framework for probing how global quantum correlations emerge from local measurement data.

We predict a supercurrent-driven Néel spin-orbit torque in a superconductor/$d$-wave altermagnet heterostructure, associated with the emergence of spin-triplet correlations. The effect can be understood as a consequence of the supercurrent-induced spin polarization, owing to the interplay between spin orbit coupling and momentum-dependent spin splitting, as found, for example, in altermagnets. Remarkably, the supercurrent can be tuned by the Néel-vector direction, and the supercurrent-induced torque can both propel magnetic domain walls and reverse the Néel-vector orientation within a domain wall. These findings establish superconductor/altermagnet heterostructures as a versatile platform for the {supercurrent-driven} control of the Néel vector, with potential applications in racetrack memory, dissipationless superconducting electronics, and unconventional computing.

Constraints on unquantized many-body holonomies, such as Wilson loops (or their Berry phases), are less explored than those on their quantized counterparts. Here, we realize an unquantized regime by tuning the bond dimerization $\delta$ and the staggered potential $\Delta$ in a half-filled dimerized staggered Hubbard ring. For the tuned parameter sets, a finite excitation gap persists along the $U(1)$ twist cycle $\theta\in[0,2\pi]$, so that the ground state $|\psi_{\delta}(\theta)\rangle$ remains separated from the excited states. The many-body Wilson loop is therefore well defined from the ground-state family $\{|\psi_{\delta}(\theta)\rangle;\,\theta\in[0,2\pi]\}$. In this setup, we show an exact many-body Wilson loop conjugation identity, $W(-\delta)=W(\delta)^*$, accumulated along a cycle parametrized by $\theta$. Importantly, the identity persists in regimes where the Berry phase $\gamma\equiv-\arg W$ varies continuously. We demonstrate the identity numerically using the density-matrix renormalization group (DMRG) method. The identity extends to other models where the flux-threaded ground-state family along the closed $\theta$-cycle is mapped to the reversed cycle. Beyond its conceptual content, the identity provides a symmetry-based consistency check for numerical evaluations of Berry phases in interacting systems. It also justifies the signal-to-noise ratio improvement in Monte Carlo simulations by performing simulations at both $\delta$ and $-\delta$ and averaging $W(\delta)$ with $W(-\delta)^{*}$.

Ultrathin films of widely different materials exhibit a dramatic enhancement of projectile penetration resistance under high–velocity impact. Despite extensive simulations and experiments, a unifying physical explanation has remained elusive. Here we show that the thickness dependence of the specific penetration energy obeys a universal law, $E_p^*(h)=E_{p,\infty}^*+B h^{-3}$, independent of chemical composition and degree of disorder. The inverse–cube scaling is traced back to a finite–size correction to the effective shear modulus arising from the suppression of long–wavelength nonaffine deformation modes in confined solids. The scaling quantitatively describes impact data for multilayer graphene, graphene oxide, and polymer thin films, revealing a common elastic origin for nanoscale impact resistance.

We report on the fabrication and characterization of patterned high-mobility two-dimensional electron gases (2DEG) formed on SrTiO$_3$ (STO) substrate surfaces by hydrogen plasma exposure. The resulting devices consistently showed high electron mobilities up to 7400 cm$^2$/V$\cdot$s. A large range of electron density was systematically explored by controlled aging of the sample between cooldowns, including the expected range for the STO 2DEG superconducting dome. No superconducting transition was observed down to the base temperature of approximately 10 mK. This suggests suppression of superconductivity in high mobility quasi-two-dimensional SrTiO$_3$ electron gas, likely linked to vertical confinement and electronic orbital rearrangement. We systematically explored electrostatic gate modulation in this 2DEG system and its scaling with electron density and side gate geometry. In contrast with our initial expectation, we observed an improvement of achievable total modulation for larger side gate to channel separation. At low electron density, stochastic channel pinch-off events were observed, creating quasi-ballistic constrictions with irregular conductance quantization. This epitaxy-free and high mobility oxide material platform offers a promising new route towards patterning quantum devices.

The thermodynamic critical field $B_{\rm c}$ provides direct access to the superconducting condensation energy, yet its pressure dependence has been studied much less extensively than that of the transition temperature. Here, muon-spin-rotation/relaxation measurements of the thermodynamic critical field $B_{\rm c}$ of elemental Pb under hydrostatic pressure up to $\simeq2.3$ GPa are reported. From the magnetic-field distribution in the intermediate state, $B_{\rm c}(T)$ is determined and $B_{\rm c}(0)$ is extracted at different pressures. In combination with previously reported high-pressure data for $B_{\rm c}$ and $T_{\rm c}$, it is shown that the pressure dependence of $B_{\rm c}(0)$ follows that of the superconducting gap $\Delta(0)$ more closely than that of the transition temperature $T_{\rm c}$. At higher pressures, the logarithmic pressure derivatives of $B_{\rm c}(0)$ and $T_{\rm c}$ are found to converge, indicating that the coupling strengths ratio $\alpha=\Delta(0)/k_{\rm B}T_{\rm c}$ becomes nearly pressure independent. This behavior is interpreted as thermodynamic evidence for a pressure-driven crossover from strong- to weak-coupling superconductivity in Pb.

Previous experimental reports of long-range interactions in ionic liquids (ILs) stand in contradiction with theoretical predictions and numerical simulations. To provide insights into the literature discrepancies regarding the experimental ranges of electrostatic screening, claimed with orders of magnitude larger, the interactions between pairs of mica and borosilicate surfaces confining ILs are investigated by two complementary advanced Surface Force Apparatuses. Regardless of differences in confinement geometries (crossed-cylinders, sphere-flat), radii of curvature (cm-mm), and measurement techniques (stepwise vs continuous approach), two ever present force regimes are evidenced. At small surface separations, oscillatory forces reflect IL structuration and layering, while outside this gap, the interaction is monotonic repulsive. In both regimes the spatial extent and force magnitude depend critically on motion conditions, as demonstrated by achieving velocities as low as 9 pm/s with equilibration times up to 90 s. At large separations, fast surface displacements generate long-range interactions (over tens of ion size) creating the illusion of anomalous underscreening, whereas increasingly slow ones shrink both magnitude and range of the repulsion with decay-lengths converging ultimately to a screening length consistent with Poisson-Boltzmann theory with finite ion sizes. The transition from apparent long-range to short-range screening unfolds over nearly two orders of magnitude in time, revealing slow relaxation dynamics reminiscent of aging phenomena. These findings definitely resolve a decade-old controversy on force measurements and reveal rich out-of-equilibrium dynamics. The hydrodynamic contribution to the net force is admittedly crucial to be reduced especially when relaxations span decades in time, but approaching thermodynamic equilibrium during measurements proves essential.

Quantum anomalies arise when symmetries of a classical theory cannot be preserved upon quantization, leading to unconventional topological responses. A prominent example is the parity anomaly of a single two-dimensional Dirac fermion, which enforces a half-quantized Hall response. Anomaly inflow mechanism allows this effect to be observed at the surfaces of three-dimensional topological insulators, however, its realization in a genuinely two-dimensional system has remained elusive. Here we report the observation of a parity-anomalous Hall response at the critical point of a quantum Hall topological phase transition in a synthetic two-dimensional system of ultracold dysprosium atoms. By coupling a continuous spatial dimension to a finite synthetic dimension encoded in atomic spin states, we engineer tunable Chern bands with C = 0 and 1. At the transition, the bulk gap closes at a single Dirac point, where we observe a robust half-quantized Hall drift despite strong non-adiabatic excitations. We show that this response originates from the global structure of the band topology, is protected by an emergent parity symmetry at criticality, and disappears when parity is explicitly broken. Our work establishes synthetic quantum systems as a powerful platform to probe quantum anomalies and their interplay with topology and non-equilibrium dynamics.