We demonstrate a magnetic quantum critical point embedded within the superconducting state of Zn-doped ${\mathrm{CeCoIn}}_5$, revealed by a pronounced peak in the magnetic penetration depth at zero temperature $\lambda (0)$. Using scanning superconducting quantum interference device microscopy, we determine the local superconducting transition temperature $T_{\mathrm{c}}$ and $\lambda (0)$. By parametrizing $\lambda (0)$ in terms of the local $T_{\mathrm{c}}$ rather than nominal Zn substitution, we circumvent the ambiguity caused by doping inhomogeneity and enable a more precise extraction of the critical exponent. The extracted effective exponent exceeds the clean spin-density-wave value, consistent with a disorder-modified quantum critical regime. The enhancement of $\lambda (0)$ reflects the suppression of the superfluid stiffness and is consistent with critical scaling. Our approach provides a route to uncover underlying quantum critical behavior obscured by inhomogeneity in unconventional superconductors.

We investigate the electronic structure at the surface of the correlated oxide ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$, a low-symmetry ruthenate oxide which hosts an unconventional polar-metal phase. From a combination of angle-resolved photoemission spectroscopy and scanning tunneling spectroscopy measurements, we demonstrate that the surface hosts an insulating phase, a distinct departure from metallicity within the bulk. Utilizing quantitative low-energy electron diffraction in conjunction with electronic structure calculations, we show how this results from a combined surface structure relaxation and the impact of marked electronic correlations in this system. Our findings highlight the proximity of ${\mathrm{Ca}}_3{\mathrm{Ru}}_2{\mathrm{O}}_7$ to an insulating metallic state, and illustrate how subtle structural distortions can control its emergent electronic phases.

Realization of a three-dimensional (3D) analog of graphene has been a central challenge in topological materials science. Graphene is stabilized by covalent bonding, unlike conventional spin-orbit-type 3D Dirac semimetals (DSMs). In this study, we demonstrate the material realization of covalent-type 3D DSMs $R_8\mathrm{Co}{X}_3$ stabilized by covalent bonding. We confirm the clean Dirac semimetal state in ${\mathrm{Y}}_8{\mathrm{CoIn}}_3$ by combined thermodynamic and transport experiments. We also realize high carrier mobility exceeding $3000{\mathrm{cm}}^2/\mathrm{Vs}$ even in polycrystalline samples of $R_8\mathrm{Co}{X}_3$. Our research provides a material platform for exploration of Dirac electrons in three dimensions with wide chemical tunability.

Mechanical metamaterials composed of bistable elements have recently emerged as promising platforms for mechanical memory. Traditional approaches to writing information in these systems typically rely on localized actuation or predefined coupling schemes, which are often labor-intensive or lack adaptability. In this Letter, we introduce a one-dimensional metamaterial consisting of mass-in-mass bistable units that are statically decoupled yet dynamically switchable, allowing arbitrary mechanical information to be encoded through nonlinear waves applied at the boundary of the system. Through a combination of experiments and simulations, we demonstrate that tailored input signals can selectively trigger state transitions deep within the structure, enabling remote and programmable bit writing. This approach opens a new avenue for mechanical memory, harnessing the robustness of bistable elements and the tunability of nonlinear wave-driven actuation.

Theoretical descriptions of the stepping-stone model, a cornerstone of spatial population genetics, have long overlooked diffusive noise arising from migration dynamics. We derive a fluctuating hydrodynamic description of this model from microscopic rules, which we then use to demonstrate that diffusive noise significantly alters early-time genetic demixing, which we characterize through heterozygosity, a key measure of diversity. Combining macroscopic fluctuation theory and microscopic simulations, we demonstrate that the scaling of allele-number fluctuations in a spatial domain displays an early-time behavior dominated by diffusive noise. Our results underscore the need for additional terms in existing continuum theories and highlight the necessity of including diffusive noise in models of spatially structured populations.

Understanding how animals move as collectives requires knowledge of movement and interaction rules implemented by individuals within such groups. We report that micro glassfish Danionella cerebrum exhibit highly dynamic schooling that is explained by a stochastic model with pairwise copying of swimming direction. We identify discrete time points that correspond directly to these copying interactions, and confirm the model’s predictions by examining the behavior of fish as they school with virtual conspecifics. The model’s success in quantitatively recapitulating group behaviors opens a door to future investigations into models of collective motion where emergent group behaviors are highly dynamic and depend strongly on group size. Furthermore, the interactions in the model serve as candidate computations implemented in the brains of individuals, facilitating future studies into the neuronal mechanisms underlying complex group behaviors.

Proper characterization of quantum correlations in multimode optical quantum states is critical for applications in quantum information science. However, standard entanglement measurements can lead to incomplete state reconstruction and characterization. Here, we implement a resonator-based detection system that reveals entanglement between sideband modes of twin beams, achieving full tomography and retrieving often ignored quantum correlations. Unlike standard spectral measurements such as homodyne detection, resonator detection can independently address the sidebands of each beam, thereby accessing these hidden correlations. Additionally, we show how phase shifts between the carrier and the sideband modes of the involved fields redistribute information and modify the observation of entanglement for different witnesses. The ability of the resonant detection to independently address sideband modes of entangled states can contribute to enhancing the capacity for secure communication and quantum networking protocols.

Recovering properties of correlation functions is typically challenging. On the one hand, experimentally, it requires measurements with a temporal resolution finer than the system’s dynamics. On the other hand, analytical or numerical analysis requires solving the system evolution. Here, we use recent results of quantum metrology with continuous measurements to derive general lower bounds on the relaxation and second-order correlation times that are both easy to calculate and measure. These bounds are based solely on steady-state expectation values and their derivatives with respect to a system parameter, and can be readily extended to the autocorrelation of arbitrary observables. We validate our method on two examples of critical quantum systems: a critical driven-dissipative resonator, where the bound matches analytical results for the dynamics, and the infinite-range Ising model, where only the steady state is solvable, and thus the bound provides information beyond the reach of existing analytical approaches. Our results can be applied to the experimental characterization of ultrafast systems and to the theoretical analysis of many-body models whose dynamics are hard to compute.

The storage of large-scale quantum information at finite temperature requires an autonomous and reliable quantum hard drive, also known as a self-correcting quantum memory. It is a long-standing open problem to find a self-correcting quantum memory in three dimensions. The recently introduced layer codes achieve the best possible scaling of code parameters and logical energy barrier in three dimensions; these are tantalizing features for the purposes of self-correction. In this Letter, we show that a family of layer codes based on good quantum Tanner codes exhibit partial self-correction. Their memory time grows exponentially with linear system size, up to a length scale that is exponential in the inverse temperature. At this length scale, the memory time scales as a double exponential of inverse temperature. To establish this result, we introduce a concatenated matching decoder that combines three rounds of parallelized minimum-weight perfect matching with a decoder for good quantum Tanner codes. We show that our decoder corrects errors up to a constant fraction of the energy barrier, and a constant fraction of the code distance, for a family of layer codes. Our results position layer codes as the leading candidate for a partially self-correcting memory in three dimensions in the asymptotically large system size regime. While they fall short of achieving strict self-correction in the thermodynamic limit, our Letter highlights the potential of these local codes in three dimensions, with fast distance and logical qubit growth, fast decoders, and a long memory time over a wide range of parameters. In particular, recent work by Gu et al. reports promising numerical results for the memory time of small explicit instances of layer codes based on random input codes.

Mapping the $S$ matrix of a generic theory of flat-space gravity coupled to matter to correlation functions of a putative Carrollian dual, we show that bulk interactions imply boundary nonlocality.

The ultrafast nonlinear optical response of molecular ensembles is fundamentally altered under strong light-matter coupling. To rigorously isolate the genuine many-body contributions, an exact time-domain field-subtraction protocol is developed within a fully nonperturbative Maxwell-Liouville framework explicitly incorporating the two-exciton manifold in real space and time. This approach reveals that while collective cavity delocalization drives the macroscopic nonlinear signal toward a severe harmonic cancellation (an effect termed “spectral starvation”), intrinsic many-body molecular interactions robustly resurrect genuine polaritonic double-quantum coherences. This many-body resurrection is governed by a universal two-photon matching rule, ${\mathrm{\Delta }}_B+4J={\mathrm{\Omega }}_R$, linking molecular anharmonicity (${\mathrm{\Delta }}_B$) to the macroscopic Rabi splitting (${\mathrm{\Omega }}_R$) and excitonic coupling ($J$). Crucially, this resonance exploits the spatial mismatch between macroscopic polaritons and localized two-exciton pairs to break harmonic cancellation. For $J$ aggregates ($J<0$), this condition uniquely isolates the resonant many-body state below the dense manifold of localized dark states, protecting the macroscopic coherence from spatial fragmentation. This predictive framework establishes a direct phase diagram to engineer and protect optical nonlinearities across diverse strongly coupled platforms.

Instabilities driven by energetic particles normally reduce fusion power, but recent studies find Alfvén eigenmode instabilities can drive “zonal” flows and currents that reduce thermal transport, improving overall performance. Motional Stark effect data from the DIII-D tokamak reveal changes in magnetic pitch angle during the phase when Alfvén-eigenmode nonlinearity drives zonal flows, suppresses microturbulence, and increases the electron and ion temperatures. Measured changes in the safety factor of $\mathrm{\Delta }q/\overline{q}\simeq 5\%$ occur in roughly 20 ms, consistent with a rough estimate based on the measured zonal flow.

The calculation of thermal conductivity in insulating solids at temperatures below the Debye temperature is problematic, due to the breakdown of classical and semiclassical approaches. In this Letter, we present a fully nonperturbative quantum methodology to compute thermal conductivity based on path integral Monte Carlo (PIMC) simulations combined with the Green-Kubo linear response theory. The method is applied to rare gas solids modeled by a Lennard-Jones potential, paradigmatic systems where quantum effects strongly affect both thermodynamic and transport properties. From PIMC simulations, we obtain the temperature-dependent phonon frequencies, lifetimes, and specific heat. From the imaginary time correlations of the energy current, we extract the thermal transport coefficients based on a physically motivated prior. We show that the experimentally observed increase of the thermal conductivity of argon and neon at low temperatures cannot be explained within a Peierls-Boltzmann framework using phonon linewidths at equilibrium. In contrast, a distinct transport lifetime emerges from the analysis of heat-current correlations. Our results demonstrate that quantum Monte Carlo methods provide a robust, nonperturbative framework to investigate heat transport in insulating solids, beyond the limits of classical molecular dynamics without relying on perturbative or semiclassical approximations.

Previous studies of incommensurate systems concluded that their critical scaling is sensitively dependent on the irrational, $\alpha$, which determines the incommensuration. Contrary to this belief, in the canonical Harper-Hofstadter model, we show there is universal $\alpha$-independent scaling for almost all $\alpha$. This critical scaling is characterized by non-power-law time-length scaling $t\sim r^{\zeta \log \log r}$. We demonstrate this in the superfluid fraction of a Bose gas, and the specific heat of a Fermi gas. This scaling is generic of a broad class of generalized Harper-Hofstadter models. The $\alpha$-independent scaling emerges as the number theoretic properties of almost all irrational numbers are statistically identical (à la Gauss-Kuzmin statistics). Consequently, we conjecture similar $\alpha$-independent scaling applies in incommensurate models more generally.

In crystalline solids, disorder breaks translational symmetry and obscures $\mathit{k}$-resolved Bloch states, limiting an accurate description of wave-function-based observables. In this Letter, we present a method that unfolds not only the band structures but also the corresponding Bloch states in disordered systems, going beyond conventional band-unfolding techniques. As a prototype application, we study defective graphene and demonstrate the capabilities by capturing key wave-function-level responses, including disorder-driven redistribution of Berry curvature.

It is widely believed that in the adiabatic limit the Fermi liquid state of an electron-phonon system, described by Migdal-Eliashberg theory, remains stable until the dressed phonon softens. Our variational and analytic analysis of the prototypical Holstein model shows that, in a wide range of fillings both in 3D and 2D, a polaronic/bipolaronic state emerges before phonon softening; at small filling in 3D this happens already at weak coupling. We show that a polaronic/bipolaronic state emerges, upon increasing coupling, via an intermediate pseudogap-type mixed state, in which some fermions retain Fermi liquid behavior, yet Luttinger’s theorem is violated. At even larger couplings the density of states gradually approaches its form in the atomic limit.

A single Landau level (LL) dressed with periodic electrostatic potentials can realize a plethora of interacting topological phases where the Hall conductivity generally does not equal to the LL filling factor. Their physics can be captured by a new family of flat topological bands: decorated Landau levels (dLLs) from imposing an electrostatic delta potential lattice within a single LL. With $p/q$ magnetic fluxes per unit cell, there are $q$ dispersive bands and $p-q$ zero-energy bands forming the dLLs. When the electrostatic potential strength dominates the electron-electron interaction, band mixing is suppressed and the dispersion bands consist of “localized states” with vanishing total Chern number. Nevertheless, these dispersive bands can have highly nontrivial Berry curvature distribution and even nonzero Chern numbers when $q>1$. Interestingly, even in the limit of large short-range interaction, band mixing between dLL and dispersive bands can be strongly suppressed at low filling factor, leading to robust topological phases within the dLLs stabilized by the one-body potential. The dLLs and the associated dispersive bands can serve as minimal theoretical models for correlated physics in lattice or moiré systems; they are also highly tunable experimental platforms for realizing rich phase diagrams of exotic 2D quantum fluids.

We demonstrate that stacking topologically trivial layers, under enforced symmetry restrictions, yields emergent topological phases with protected boundary states. Remarkably, the number of layers itself acts as a topological switch, enabling the system to host topological bound states in the continuum (BICs). Analytically, we reveal that an odd-layer configuration not only renders the spectrum gapless but also supports BICs protected by interlayer reflection symmetry. Combined with entanglement-spectrum calculations, this confirms that odd-layer systems indeed support topological BICs. We provide experimental confirmation of these topological states in stacked acoustic lattices. Our findings establish a previously overlooked pathway to topology and demonstrate a readily applicable strategy for realizing exotic states in a wide range of artificial material systems.