Hysteresis, with rich dynamical behaviors—especially in interacting systems—has drawn broad research interest. Yet its dynamic scalings across timescales lack a unified description, and their transitions remain unclear. Here, we study the stochastic ${\varphi }^4$ model driven periodically by an external field $H$. For large systems with small noise strength $\sigma$, we find the coercivity $H_c\equiv H(⟨\varphi ⟩=0)$ sequentially exhibits distinct behaviors with increasing driving rate $v_H$: $v_H$-scaling increase, stable plateau ($v_H^0$), $v_H^{1/2}$-scaling increase, and abrupt decline to disappearance. The plateau reflects the competition between thermodynamic and quasistatic limits, namely, ${\lim }_{\sigma \to 0}{\lim }_{v_H\to 0}{H}_c=0$, and ${\lim }_{v_H\to 0}{\lim }_{\sigma \to 0}{H}_c=H^{*}$. Here, $H^{*}$ is exactly the field-driven first-order phase transition point. In the post-plateau regime, $(H_c-H_P)$ scales with $(v_H-v_P{)}^{2/3}$ with $v_P$ and $H_P$ being the reference points of the plateau. Moreover, we reveal a finite-size scaling for the coercivity plateau as $v_P\sim {\sigma }^2$ and $(H^{*}-H_P)\sim {\sigma }^{4/3}$ by utilizing renormalization-group theory. Our Letter provides a panoramic view of finite-time scalings of the hysteresis and offers new insights into the interplay between finite-time and finite-size effects in nonequilibrium systems.

Understanding different aspects of time is at the core of many areas in theoretical physics. Minimal models of continuous stochastic and quantum clocks have been proposed to explore fundamental limitations on the performance of timekeeping devices. Owing to the level of complexity in the clock structure and its energy consumption, such devices show trade-offs whose characterization remains an open challenge. Indeed, even conceptual designs for thermodynamically efficient quantum clocks are not yet well understood. In condensed matter theory, time crystals were found as an exciting new phase of matter featuring oscillations in (pseudo) equilibrium with first experimental observations appearing recently. This naturally prompts the question: Can time crystals be used as quantum clocks, and what is their performance from a thermodynamic perspective? We answer this question and find that quantum time crystals are indeed genuine quantum clocks with a performance enhanced by the spontaneous breaking of time-translation symmetry.

Because they are likely to accrete substantial amounts of interstellar gas, merging supermassive binary black holes are expected to be strong multimessenger sources, radiating gravitational waves, photons from thermal gas, and photons from relativistic electrons energized by relativistic jets. Here we report on a numerical simulation that covers the late inspiral, merger, and initial postmerger phase of such a system where both black holes have the same mass and spin, and both spin axes are parallel to the orbital angular momentum. The simulation incorporates both 3D general relativistic magnetohydrodynamics and numerical relativity. The thermal photon power during the late inspiral, merger, and immediate postmerger phases is drawn from strong shocks rather than dissipation of turbulence inside a smoothly structured accretion disk as typically found around accreting single black holes. We find that the thermal photon and jet Poynting flux outputs are closely related in time, and we posit a mechanism that enforces this relation. The power radiated in both photons and jets diminishes gradually as merger is approached, but jumps sharply at merger to a noisy plateau. Such a distinct lightcurve should aid efforts to identify supermassive black hole mergers, with or without accompanying gravitational wave detections.

Superluminous supernovae (SLSNe) are a new class of transients with luminosities $\sim 10–100$ times larger than the usual core-collapse supernovae. Their origin is still unclear. One widely discussed scenario involves a millisecond magnetar central engine. The GeV-TeV emission of SLSNe has been predicted in the literature but has not been convincingly detected yet. Here, we report the results of the search for $\gamma$-ray emission in the direction of SN 2017egm, one of the closest SLSNe detected so far, using 15 years of Fermi-LAT Pass 8 data. There is a transient $\gamma$-ray source appearing about two months after this event and lasting a few months. Monte Carlo simulations show that the $\gamma$-ray signal has a global significance of at least $4\sigma$. Both the peak time and the luminosity of the GeV emission are consistent with the magnetar model prediction, suggesting that such a GeV transient is the high-energy counterpart of SN 2017egm and the central engine of this SLSNe is a young magnetar.

In 1996, Hatano and Nelson proposed a non-Hermitian lattice model containing an imaginary Peierls phase [Phys. Rev. Lett. 77, 570 (1996)], which subsequent analyses revealed to be an instance of a new class of topological systems. Here, we experimentally realize a continuum analog to this model containing an imaginary gauge potential using a homogeneous spin-orbit coupled Bose-Einstein condensate (BEC). Non-Hermiticity is introduced by adding tunable spin-dependent loss via microwave coupling to a subspace with spontaneous emission. We demonstrate that the resulting Heisenberg equations of motion for position and momentum depend explicitly on the system’s phase-space distribution. First, we observe collective nonreciprocal transport in real space, with a “self-acceleration” that decreases with the BEC’s spatial extent, consistent with non-Hermitian Gross-Pitaevskii simulations. We then examine localized edge states: the relatively strong interactions in our BEC suppress the formation of topological edge states, yielding instead highly excited states localized by an interplay between self-acceleration and wave function spreading. Finally, we confirm that our non-Hermitian description remains valid at all times by comparing it to a multilevel master equation treatment.

While THz pulses with durations close to a single oscillation period are widely regarded as optimal stimuli for achieving the fastest and most energy-efficient control of spins in magnetic materials, all-dielectric metasurfaces have recently been demonstrated to provide the least dissipative platform for enhancing and controlling light-spin coupling. All-dielectric metasurfaces for the THz control of spins hold great potential in the field of spintronics and related technologies, pushing the boundaries of speed and energy efficiency in spin-based information processing. Here, we introduce and demonstrate a novel material: a specially designed dielectric metasurface for an advanced THz control of spins in a ferrimagnetic film of iron garnet. By structuring a nonmagnetic substrate, one can force a THz electromagnetic field, otherwise described by plane waves, to acquire an out-of-plane magnetic field and thus enable arbitrary direction of the torque acting on spins in all three dimensions. Hence, metaphotonics opens up a plethora of opportunities for advanced control of spins at THz rates in many hot fields of contemporary science, including spintronics, magnonics, and quantum computing.

Entanglement is crucial for quantum networks and computation, yet maintaining high-fidelity entangled quantum states is hindered by decoherence and resource-intensive purification methods. Here, we experimentally demonstrate entanglement pumping, utilizing bosonic quantum error correction (QEC) codes as long-coherence-time storage qubits. By repetitively generating entanglement with short-coherence-time qubits and injecting it into error-detectable logical qubits, our approach effectively preserves entanglement. Through error-detection to discard error states and entanglement pumping to mitigate errors within the code space, we extend the existence time of entanglement by nearly 50% compared to the case without entanglement pumping. This entanglement pumping scheme can additionally serve as an erasure detection protocol for the dual-rail code. This Letter highlights the potential of bosonic logical qubits for scalable quantum networks and introduces a novel paradigm for efficient entanglement management.

Superconductivity can be destroyed by a magnetic field with an upper bound known as the Pauli limit. Here, we report a large violation of the Pauli limit in both in-plane and perpendicular magnetic fields in ${\mathrm{La}}_{0.8}{\mathrm{Sr}}_{0.2}{\mathrm{NiO}}_2$ infinite-layer superconducting thin films. The critical field $H_{\mathrm{c}2}$ shows a clear anisotropic behavior and a pronounced upturn at ultralow temperatures, manifesting anisotropic superconductor-metal transition features. Scaling analysis near the $\mathit{T}\to 0$ quantum critical point of this transition reveals a quantum Griffiths singularity arising from quenched disorder, hallmarked by a diverging dynamic critical exponent. These quantum Griffiths singularity induced quantum fluctuations provide the origin for the pronounced $H_{\mathrm{c}2}$ upturn and represent a key intrinsic mechanism for the robust violation of the Pauli limit. Our findings establish a microscopic mechanism where heavy-fermion mass renormalization suppresses orbital pair breaking, enabling disorder-enhanced quantum fluctuations to preserve superconductivity far beyond the Pauli limit.

We present Coulomb-drag measurements on a heterostructure comprising two Bernal-stacked bilayer graphene (BLG) sheets separated by a 2.5 nm hexagonal boron nitride (hBN) spacer in the quantum Hall (QH) regime. Using top and bottom gate control, together with an interlayer bias, we independently tune the two BLG layers into either the lowest ($N=0$) or second ($N=1$) Landau level (LL) orbital and probe their interlayer QH states. When both layers occupy the $N=0$ orbital, we observe both interlayer exciton condensates (ECs) at integer total filling and interlayer fractional QH states, echoing the results in double monolayer graphene. In contrast to previous studies, however, when both BLG layers occupy the $N=1$ orbital, we also observe quantized drag signals, signifying an interlayer exciton condensate formed between the second LLs. By tuning the layer degree of freedom, we find that this $N=1$ EC state arises only when the $N=1$ wave function in each BLG is polarized toward the hBN interface to maximize the interlayer Coulomb interaction.

Tungsten diboride (${\mathrm{WB}}_{2+x}$) has been predicted to be a superhard material. It, however, has yet to be practically realized, because of its intrinsically low toughness, without involving favorable dislocation slip systems. Here, we report a viable strategy to effectively strengthen both the toughness and hardness of ${\mathrm{WB}}_{2+x}$ by introducing ordered atomic vacancies to increase dislocation mobility along certain directions. By doping with rhenium atoms, the ordered metal-vacancy pairs are revealed to occur extensively in the optimally doped sample with a composition of ${({\mathrm{W}}_{0.9}{\mathrm{Re}}_{0.1})}_{1-\delta }{\mathrm{B}}_{2+x}$ synthesized under high pressure. Such vacancy pairs are found to mainly reside in the $\{210\}$ and $\{102\}$ planes, along which the long-range dislocations are kinetically favored for improving its toughness and plasticity to achieve a load-invariant superhardness of $\sim 40\mathrm{GPa}$. In addition, its thermal stability is drastically promoted and rivals that of cubic boron nitride ($c\mathrm{BN}$). These discoveries not only experimentally identify a superhard material but also provide powerful insights into how the mechanical properties of transition-metal diborides can be improved by tailoring atomic deficiencies.

Negative Poisson’s ratio (NPR) is rare in crystalline solids, and its microscopic origin in oxide perovskites remains elusive. Here we use first-principles calculations to investigate the auxetic response of prototypical ferroelectrics ${\mathrm{PbTiO}}_3$ and ${\mathrm{BaTiO}}_3$ (BTO). We show that NPR is governed by local polar ionic displacements, which stabilize cation-anion bonding environment under deformation and can reverse the sign of the Poisson’s ratio. In particular, NPR in both the tetragonal and cubic phases of BTO emerges only in structures exhibiting local Ti off centering along the $⟨111⟩$ directions, whereas the conventional [001]-polarized tetragonal phase and the high-symmetry cubic structure display positive Poisson’s ratios. Our results establish local polarization as the microscopic origin of NPR in ferroelectrics and highlight it as a tunable parameter for designing auxetic functionality in perovskite oxides.

The energy density generated by a vector current is characterized by a single parameter $a_{\mathcal{E}}$ bounded by unitarity to $-1/2\le a_{\mathcal{E}}\le 1$, with extremal values saturated by free theories of different matter content. Through confinement, QCD transmutes fermionic matter into scalars, revealing a nontrivial flow between extremal correlators. We reconstruct this flow using perturbative QCD and chiral perturbation theory. The observable is accessible with currently available experimental data.

Photonic molecules can mimic interactions of atomic energy levels, offering new ways to manipulate cavity eigenstates. Current methods using evanescent coupling of multiple cavities face challenges in scalability, flexibility, and coupling control, especially for complex systems. Here we introduce a new method that uses a single multimode optical ring resonator to create photonic molecules. Our design uses multiple waveguide transverse modes in one resonator, providing flexibility to engineer complex interactions without typical coupling constraints. We demonstrate arbitrary intermode coupling through transmissive mode converters, allowing precise tuning of resonance splitting and intrinsic losses. This approach enables selective bright-dark mode pair generation and the exploration of novel photonic phenomena such as exceptional points. This multimode photonic molecule overcomes traditional limitations and offers new possibilities for integrated photonic circuits, optical processing, and studies in non-Hermitian and nonlinear photonics.

The first-passage time (FPT) of a stochastic signal to a threshold is a fundamental observable across physics, biology, and finance. While renewal shot noise is a canonical model for such signals, analytical results for its FPT have remained confined to the Poisson (Markovian) case, even though non-Poisson arrival statistics are common in systems from neuronal spiking to gene expression. Here, we overcome this long-standing limitation by deriving a universal asymptotic formula for the mean FPT $⟨T_b⟩$ to reach level $b$ for renewal shot noise with arbitrary arrival statistics and exponential marks. Our central result is a simple, closed-form expression that exposes the physical mechanism by which temporal correlations in arrivals modulate the baseline Arrhenius law. We show that bursty arrivals introduce universal scaling corrections that markedly accelerate threshold crossings. In turn, nonbursty arrivals remain Arrhenius-like, directly linking temporal burstiness to Arrhenius scaling. Furthermore, we show and confirm numerically that the full FPT distribution becomes exponential at large thresholds, implying that $⟨T_b⟩$ provides a complete asymptotic characterization. Our Letter, enabled by a novel exact expression for the moments of the noise, establishes a general framework for analyzing extreme events in non-Markovian systems with relaxation.

The application of a magnetic field has emerged as an effective method for studying the spin-related effects in the oxygen evolution reaction (OER). However, the presence of spin-unrelated effects under a magnetic field also contributes to the observed OER increment, complicating the identification of spin-related enhancement. This is primarily associated with the intrinsic limitation of the conventional magnetic catalysts that require the continuous application of an external magnetic field to maintain the magnetization. Here, we have developed magnetron-sputtered $\mathrm{Co}/\mathrm{PtCo}$ multilayer catalysts with perpendicular magnetic anisotropy, enabling a stable magnetization state without continuous magnetic fields. The magnetic anisotropy of the multilayers is controlled through the number of repetitions of $\mathrm{Co}/\mathrm{PtCo}$ bilayers. As the bilayer number increases from 2 to 25, the domain size at the demagnetized state gradually reduces to the nanometer scale due to the enhanced magnetostatic energy. Upon premagnetization with out-of-plane magnetic fields, the pure spin-enhanced OER is numerically correlated to the change in domain wall ratios, where the global non-spin-related enhancement is effectively excluded. Such spin-enhanced OER is found to be favored by magnetic anisotropy due to the higher magnetic stability to maintain the magnetization state. This Letter provides a new strategy for achieving stable spin-related OER enhancement by magnetic anisotropy, advancing magnetic-field-free spin electrocatalysts to optimize OER performance.

The distribution of absorption lines in the spectra of distant quasars, called the Lyman-$\alpha$ (Ly-$\alpha$) forest, is a unique probe of cosmology and the intergalactic medium at high redshifts and small scales. The statistical power of ongoing redshift surveys demands precise theoretical tools to model the Ly-$\alpha$ forest. We address this challenge by developing an analytic, perturbative forward model to predict the Ly-$\alpha$ forest at the field level for a given set of cosmological initial conditions. Our model shows a remarkable performance when compared with the Sherwood hydrodynamic simulations: it reproduces the Ly-$\alpha$ forest flux power spectrum, its cross-correlation with dark matter halos, and the one-point probability distribution function of both fields at the percent level down to scales of a few Mpc. Our work provides crucial tools that bridge analytic modeling on large scales with simulations on small scales, enabling field-level inference from Ly-$\alpha$ forest data and simulation-based priors for cosmological analyses. This is especially timely for realizing the full scientific potential of the Ly-$\alpha$ forest measurements by the dark energy spectroscopic instrument.

Recent experiments reported evidence of superconductivity and reentrant integer quantum anomalous Hall (RIQAH) insulator upon doping the ${\nu }_e=2/3$ fractional quantum anomalous Hall states (FQAHs) in twisted ${\mathrm{MoTe}}_2$, separated by narrow resistive regions. Anyons of an FQAH generally have a finite effective mass and, when described by anyon-flux composite fermions (CFs), experience statistical magnetic fields with a commensurate filling. Here, we show that most of the experimental observations can be explained by invoking the effects of disorder on the Landau-Hofstadter bands of CFs. In particular, by making minimal assumptions about the anyon energetics and dispersion, we show that doping anyons drives plateau transitions of CFs into integer quantum Hall states, which physically corresponds to either a superconductor or to an RIQAH phase. We develop a dictionary that allows us to infer the response in these phases and the critical regions from the knowledge of the response functions of the plateau transitions. In particular, this allows us to relate the superfluid stiffness of the superconductor to the polarizability of CFs. As a first step toward a quantitative understanding, we borrow results from the celebrated integer quantum Hall plateau transitions to make quantitative predictions for the critical behavior of the superfluid stiffness, longitudinal and Hall conductivity, and response to out-of-plane magnetic field, all of which agree reasonably well with the experimental observations. Our results provide strong support for anyon superconductivity being the mechanism for the observed superconductor in the vicinity of the ${\nu }_e=2/3$ FQAH insulator.

Excitonic band structure is critical for investigating exciton dynamics. Theoretically, quantum effects from exchange scattering between electron-hole pairs significantly modulate exciton dispersion. Here, we report the direct observation of dimensionality-dependent exciton dispersion in a single-band Mott insulator ${\mathrm{Nb}}_3{\mathrm{Cl}}_8$ through high-resolution electron energy loss spectroscopy. In the high-temperature phase, the exciton in ${\mathrm{Nb}}_3{\mathrm{Cl}}_8$ hosts an exceptionally large binding energy, and exhibits clear quasi-two-dimensional massless linear dispersion. In contrast, in the low-temperature phase, the exciton splits into two bands, both displaying three-dimensional parabolic dispersion. These dramatic changes in the exciton dispersion stem from the dimensional mutation driven by a substantial enhancement of interlayer coupling across the phase transition. This Letter provides a clear and typical example of how exciton behavior evolves with dimensionality.

Understanding the folding mechanisms of biomolecules, such as proteins and nucleic acids, requires probing time-dependent changes of conformations, including secondary and tertiary structure formation. All these mechanism-relevant structural transitions, typically seen as coarse-grained descriptions in molecular dynamics simulations, occur in the tiny fraction of a molecular trajectory called the transition path (TP). However, TPs have been inaccessible for most proteins due to the limited time resolution of single-molecule techniques. Here, we measure the TP times of eight two-state single-domain proteins in aqueous solution using nanophotonics-enhanced single-molecule fluorescence spectroscopy. We found that the TP times are extremely short, ranging from 0.7 to $4\mathrm{\mu }\mathrm{s}$, and insensitive to most protein properties. Surprisingly, however, the extracted diffusion coefficient at the free energy barrier on the number of native contacts coordinate increases with protein length. This facilitation of diffusion in larger proteins is explained by increased cooperative native contact formation during folding, which reduces the roughness of the energy landscape. Our results reveal that evolutionary optimization of the energy landscape is much more efficient for protein folding than for other biomolecular processes.

Manipulating the frequency and bandwidth of light is crucial in classical and quantum applications including communication, spectroscopy, imaging, and signal processing. Such capabilities also offer potential for interfacing disparate quantum systems in quantum networking and for quantum information processing. We experimentally demonstrate deterministic, broadband frequency control of heralded telecom-band single photons via cross-phase modulation in a short length of single-mode fiber. An intense, ultrafast pump pulse imposes a transient, intensity-dependent refractive-index gradient which imparts a tunable phase shift on the single photons. We present absolute frequency shifts of up to $+6.42\pm 0.06\mathrm{THz}$ and $-5.82\pm 0.02\mathrm{THz}$, and bandwidth manipulation ranging from a factor of $0.76\pm 0.03$ to $7.1\pm 0.4$ times that of the input. Spectral measurements are acquired with a time-of-flight spectrometer and superconducting nanowire detectors. Our scheme offers a compact and scalable route to spectral routing and bandwidth engineering for ultrafast quantum networking and quantum information processing.