We investigate the steady state phase diagram of fermionic atoms subjected to an optical lattice and coupled to a high finesse optical cavity with photon losses. The coupling between the atoms and the cavity field is induced by a transverse pump beam. Taking fluctuations around the mean-field solutions into account, we find that a transition to a self-organized phase takes place at a critical value of the pump strength. In the self-organized phase the cavity field takes a finite expectation value and the atoms show a modulation in the density. Surprisingly, at even larger pump strengths two self-organized stable solutions of the cavity field and the atoms occur, signaling the presence of a bistability. We show that the bistable behavior is induced by the atoms-cavity fluctuations and is not captured by the mean-field approach.

Anisotropic pair breaking close to surfaces favors the chiral $A$ phase of the superfluid ${}^3\mathrm{He}$ over the time-reversal invariant $B$ phase. Confining the superfluid ${}^3\mathrm{He}$ into a cavity of height $D$ of the order of the Cooper pair size characterized by the coherence length ${\xi }_0$—ranging between 16 nm (34 bar) and 77 nm (0 bar)—extends the surface effects over the whole sample volume, thus allowing stabilization of the $A$ phase at pressures $P$ and temperatures $T$ where otherwise the $B$ phase would be stable. In this Letter, the surfaces of such a confined sample are covered with a superfluid ${}^4\mathrm{He}$ film to create specular quasiparticle scattering boundary conditions, preventing the suppression of the superfluid order parameter. We show that the chiral $A$ phase is the stable superfluid phase under strong confinement over the full $P\text{−}T$ phase diagram down to a quasi-two-dimensional limit $D/{\xi }_0=1$, where $D=80\mathrm{nm}$. The planar phase, which is degenerate with the chiral $A$ phase in the weak-coupling limit, is not observed. The gap inferred from measurements over the wide pressure range from 0.2 to 21.0 bar leads to an empirical ansatz for temperature-dependent strong-coupling effects. We discuss how these results pave the way for the realization of the fully gapped two-dimensional $p_x+i{p}_y$ superfluid under more extreme confinement.

The recent observation of high-$T_c$ superconductivity in the bilayer nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure has garnered significant interest. While researches have predominantly focused on the role of electron-electron interactions in the superconducting mechanism, the impact of electron-phonon coupling (EPC) has remained elusive and unexplored. In this Letter, we perform first-principles calculations to study the phonon spectrum and electron-phonon coupling within ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure and explore the interplay between EPC and electronic interactions on the superconductivity by employing functional renormalization group (FRG) approach. Our calculations reveal that EPC alone is insufficient to trigger superconductivity in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ under pressure. We identify unique out-of-plane and in-plane breathing phonon modes which selectively couple with the Ni $d_{z^2}$ and $d_{x^2-y^2}$ orbitals, showcasing an orbital-selective EPC. Within the bilayer two-orbital model, it is revealed that solely electronic interactions foster $s_{\pm }$-wave pairing characterized by notable frustration in the band space, leading to a relatively low transition temperature. Remarkably, we find that the out-of-plane EPC can act in concert with electronic interactions to promote the interlayer pairing in the $d_{z^2}$ orbital, partially releasing the pairing frustration and thus elevating $T_c$. In contrast, the inclusion of in-plane EPC only marginally affects the superconductivity, distinct from the cuprates. Potential experimental implications in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ are also discussed.

The band-projected density operators in a Landau level obey the Girvin-MacDonald-Platzman (GMP) algebra, and a large amount of effort in the study of fractional Chern insulators has been directed toward approximating this algebra in a Chern band. In this Letter, we prove that the GMP algebra, up to form factors, is the only closed algebra that projected density operators can satisfy in two and three dimensions, highlighting the central place it occupies in the study of Chern bands in general. A number of interesting corollaries follow.

Recently, superconductivity has been observed in twisted ${\mathrm{WSe}}_2$ moiré structures (Xia et al., Nature (London) 637, 833 (2025); Guo et al., Nature (London) 637, 839 (2025)). Its transition temperature is high, reaching a few percent of the Fermi temperature scale. Here, we advance a mechanism for superconductivity based on the notion that electronic topology enables quantum fluctuations in a suitable regime of intermediate correlations. In this regime, the Coulomb interaction requires that an active topological flat band and nearby wider bands are considered together. Compact molecular orbitals arise, which give rise to quantum fluctuations through topology-dictated hybridization with the other molecular orbitals. The hybridization competes with the active flat band’s natural tendency toward static electronic ordering, thereby weakening the latter; we link this effect with certain salient observations by experiments. Furthermore, the competition yields a quantum critical regime where quasiparticles are lost. The corresponding quantum critical fluctuations drive superconductivity. Broader implications and new connections among correlated materials platforms are discussed.

The synergistic control of light’s frequency and orbital angular momentum (OAM) via integrated nonlinear ring microresonators is crucial for creating spatiotemporal optical waveforms and advancing optical metrology. A direct analog of this capability in acoustics is challenging due to the nonlinearity-based mechanisms’ dependence on external driving and limited frequency conversion efficiency. Here, we present an acoustic synthesized comb structure derived from spatiotemporal metasurfaces, concurrently controlling frequency and OAM characteristics with high conversion efficiency and removing the constraints of critical driving frequency and power level in nonlinear mechanisms. By optimizing comb structures, energy distributions among OAM modes are adjusted to different frequency lines. We finally propose spatiotemporal metalens devices based on vortex-frequency combs, enabling synchronously multiple-order spatial differential operations for parallel data processing. This Letter is groundbreaking in integrating spectral- and spatial-domain acoustic waves, promising multifunctional imaging and advantages in spatiotemporal beams.

Using simulations, we demonstrate how a liquid-liquid phase transition (LLPT) manifests in supercooled water nanodroplets. Selecting an interaction potential for which a LLPT occurs in the bulk liquid, we conduct simulations of supercooled water nanodroplets having between 1000 and 80000 molecules. We show that as the droplet size decreases, the Laplace pressure grows large enough to drive the droplets through the transition from the low-density to the high-density liquid phase, and that all droplets in this size range are large enough to have cores exhibiting the structure and properties of bulk water. To guide experiments, we estimate the range of values for the critical pressure of the LLPT in real water that can be observed using nanodroplets, and propose structural and dynamical measures by which the LLPT in nanodroplets can be detected.

Cell cortex contraction is vital for shaping cells, enabling movement, division, and responding to mechanical signals–processes crucial for multicellular organisms. Differential membrane contractions between cells significantly influence segregation. We present a model where active particle rings interact through differential contraction, showing that segregation arises from this mechanism, with ring activity functioning as an effective temperature. The interface decay exponent is close to $\lambda \sim 1/3$, differing from previous cluster fusion and diffusion model predictions.

Long-range interactions are a key resource in many quantum phenomena and technologies. Free-space photons mediate power-law interactions but lack tunability and suffer from decoherence processes due to their omnidirectional emission. Engineered dielectrics can yield tunable and coherent interactions, but typically at the expense of making them both shorter ranged and sensitive to material disorder and photon loss. Here, we propose a platform that can circumvent all these limitations based on three-dimensional subwavelength atomic arrays subjected to magnetic fields. Our key result is to show how to design the polaritonic bands of these atomic metamaterials to feature a pair of frequency-isolated Weyl points, i.e., points in reciprocal space around which the bands disperse linearly and defining monopoles of the Berry curvature. As predicted by recent works, such Weyl excitations can mediate interactions that are simultaneously long range, due to their gapless nature; robust, due to the topological protection of Weyl points; and decoherence-free, due to their subradiant character. We demonstrate the robustness of these isolated Weyl points for a large regime of interatomic distances and magnetic field values and characterize the emergence of their corresponding Fermi arcs surface states. The latter can lead to two-dimensional, nonreciprocal atomic interactions with no analogue in other chiral quantum optical setups.

The formation of nontrivial braid structures of complex energies enables a new topological classification beyond conventional topological band theory. In this Letter, we introduce the concept of braiding topology to dynamic systems and reveal novel Floquet-Bloch braids in non-Hermitian spatiotemporal lattices. This nonequilibrium braiding topology, closely related to the breakdown of continuous time translation symmetry, is characterized by an invariant derived from Floquet operators. In sharp contrast to static lattices, the Floquet-Bloch braids can be directly manipulated using temporal engineering, enabling an arbitrary braiding degree even in a two-band lattice without long-range hopping. Experimentally, we synthesize Floquet-Bloch bands in an acoustic platform with time-modulated unidirectional couplers. We not only realize a series of Floquet-Bloch braids with distinct topologies, but also observe the transition states featuring state-coalesced Floquet exceptional points. Our findings reveal a fundamental interplay between non-Hermiticity and Floquet engineering, and pave the way for experimentally exploring the rich and uncharted territory of nonequilibrium non-Hermitian physics.

We experimentally explore the interfacial coherent spin pumping in the magnon-magnon hybridized regime of a perpendicular anisotropy ferrimagnetic insulator (Bi-substituted yttrium iron garnet, or BiYIG) and ferromagnetic metal (permalloy, or Py) bilayer. In addition to the interfacial exchange coupling-induced avoided crossings between the uniform modes of BiYIG and Py, we observe that the gap opening can be tailored by changing the relative orientations of the BiYIG and Py magnetizations due to a purely dynamic interaction. The avoided-crossing gap opening is small (large) when BiYIG and Py magnetizations are nearly perpendicular (partially collinear) to each other, indicating that interfacial fieldlike torque from spin pumping plays a dominant role. Macrospin simulations with a sizable fieldlike spin-pumping torque agree with the gap opening trend observed in the experiments.

At criticality, the magnetization $M$ of a $d$-dimensional Ising system with $N$ spins is distributed such that the probability density function of $m=M/N^{y_H/d}$, with $y_H$ universal exponent, converges to a limit $f(m)$. The expectation that $f$ should furnish a hallmark of universal behavior contrasts with its sensible dependence on nonuniversal features. We show that both nonuniversal amplitudes and universal exponents of leading power law singularities in all large deviation functions are determined by the fact that, due to extensivity, $f(m){\sim }_{|m|\gg 1}\exp (-c|m{|}^{\delta +1})$, with $\delta =y_H/(d-y_H)$ and $c$ a nonuniversal coefficient. This unexplored scenario implies a universal form of central limit theorem at criticality and is confirmed by exact calculations for mean field Ising models in equilibrium and for anomalous diffusion models, with $M$ replaced by displacement and $N$ by time.

Recent advancements in quantum hardware and classical computing simulations have significantly enhanced the accessibility of quantum system data, leading to an increased demand for precise descriptions and predictions of these systems. Accurate prediction of quantum Hamiltonian dynamics and identification of Hamiltonian parameters are crucial for advancements in quantum simulations, error correction, and control protocols. This Letter introduces a machine learning model with dual capabilities: it can deduce time-dependent Hamiltonian parameters from observed changes in local observables within quantum many-body systems, and it can predict the evolution of these observables based on Hamiltonian parameters. Our model’s validity was confirmed through theoretical simulations across various scenarios and further validated by two experiments. Initially, the model was applied to a nuclear magnetic resonance quantum computer, where it accurately predicted the dynamics of local observables. The model was then tested on a superconducting quantum computer with initially unknown Hamiltonian parameters, successfully inferring them. Our approach aims to enhance various quantum computing tasks, including parameter estimation, noise characterization, feedback processes, and quantum control optimization.

We show that bipartite bound entangled states make possible violations of correlation inequalities in the prepare-and-measure scenario. These inequalities are satisfied by all classical models as well as by all quantum models that do not feature entanglement. In contrast to the known Bell inequality violations from bound entangled states, we find that the violations in the prepare-and-measure scenario are sizeable and significantly noise-tolerant. Furthermore, we show that significantly stronger quantum correlations are made possible by considering bound entanglement with a larger dimension.

Critical ground states of quantum many-body systems have emerged as vital resources for quantum-enhanced sensing. Traditional methods to prepare these states often rely on adiabatic evolution, which may diminish the quantum sensing advantage. In this Letter, we propose a quantum reinforcement learning (QRL) enhanced critical sensing protocol for quantum many-body systems with exotic phase diagrams. Starting from product states and utilizing QRL-discovered gate sequences, we explore sensing accuracy in the presence of unknown external magnetic fields, covering both local and global regimes. Our results demonstrate that QRL-learned sequences reach the finite quantum speed limit and generalize effectively across systems of arbitrary size, ensuring accuracy regardless of preparation time. This method can robustly achieve Heisenberg and super-Heisenberg limits, even in noisy environments with practical Pauli measurements. Our study highlights the efficacy of QRL in enabling precise quantum state preparation, thereby advancing scalable, high-accuracy quantum critical sensing.

A dedicated search for upward-going air showers at zenith angles exceeding 110° and energies $E>0.1\mathrm{EeV}$ has been performed using the Fluorescence Detector of the Pierre Auger Observatory. The search is motivated by two “anomalous” radio pulses observed by the ANITA flights I and III that appear inconsistent with the standard model of particle physics. Using simulations of both regular cosmic-ray showers and upward-going events, a selection procedure has been defined to separate potential upward-going candidate events and the corresponding exposure has been calculated in the energy range [0.1–33] EeV. One event has been found in the search period between January 1, 2004, and December 31, 2018, consistent with an expected background of $0.27\pm 0.12$ events from misreconstructed cosmic-ray showers. This translates to an upper bound on the integral flux of $(7.2\pm 0.2)\times {10}^{-21}{\mathrm{cm}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{y}}^{-1}$ and $(3.6\pm 0.2)\times {10}^{-20}{\mathrm{cm}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{y}}^{-1}$ for an $E^{-1}$ and $E^{-2}$ spectrum, respectively. An upward-going flux of showers normalized to the ANITA observations is shown to predict over 34 events for an $E^{-3}$ spectrum and over 8.1 events for a conservative $E^{-5}$ spectrum, in strong disagreement with the interpretation of the anomalous events as upward-going showers.