Whether brain dynamics operate near a critical regime remains a central question in neuroscience, with potential implications for information processing and computational flexibility. However, conventional approaches are susceptible to artifacts introduced by temporal correlations, spatial dependencies, and subsampling, which can create the illusion of scaling in noncritical systems. Here we introduce an analytical and numerical framework centered on the covariance matrix and its spectrum, combined with a phenomenological renormalization group (PRG) approach, and extended to incorporate colored inputs, temporal and spatial correlations, and robust inference and control strategies for empirical data. Applying this framework to pooled resting-state fMRI, we find that collective brain activity is slightly subcritical yet close to criticality. The extracted exponents are robust and align with predictions from recurrent firing-rate models in the long-time correlation limit. Beyond these results, our Letter provides methodological tools for more reliable tests of criticality in neuroscience and complex systems.

Isomer depletion serves as a prerequisite for a variety of important applications. Several mechanisms are proposed to trigger the isomer depletion. In the previous work [Chiara et al., Nature (London) 554, 216 (2018).], isomer depletion with an exceptionally high probability in ${}^{93m}\mathrm{Mo}$ was reported and attributed to nuclear excitation by electron capture (NEEC). However, contradictory probability values were subsequently reported from both experimental and theoretical aspects. This Letter reports a new and more precise measurement of the isomer depletion of high-energy ${}^{93m}\mathrm{Mo}$ ions during the slowing-down processes in lead and carbon foils via a low-background beam-based experimental approach. By employing a purified isomer beam, the depletion probabilities are determined to be $2.0(2)\times {10}^{-5}$ in lead and $4.7(13)\times {10}^{-6}$ in carbon, agreeing well with the inelastic nuclear scattering calculations. We conclude that the observed isomer depletion in ${}^{93m}\mathrm{Mo}$ arises from inelastic nuclear scattering rather than the previously proposed NEEC mechanism.

Solitons are the cornerstone of nonlinear physics. The integrability of nonlinear equations is the basis of this universal concept. However, most multidimensional systems lack integrability, a fundamental limitation that challenges the existence of solitons in high dimensions. A remarkable exception would be the lump soliton, a two-dimensional solution of the Kadomtsev-Petviashvili (KP) equation with the unique property of propagating unperturbed in three-dimensional space. Due to the difficulty of implementing the KP dynamics in any physical system, lump solitons have never been observed. Here, we report the first experimental observation of the lump soliton. The lump is realized in nonlinear optics, in a photorefractive crystal under the action of paraxial diffraction and defocusing nonlinearity, ruled by the $(2+1)\mathrm{D}$ nonlinear Schrödinger (NLS) equation. We tailor the input field shape and the nonlinearity to realize the hydrodynamic KP integrable regime of the NLS equation. The lump emerges as a self-localized wave that propagates unaltered with a transverse velocity. We confirm its integrable nature by reporting, for the first time, the elastic collision of lumps in two dimensions. As the first experimental evidence of integrable solitons in high dimensions, our observation paves the way for a new era in the study of nonlinear systems.

An acoustic standing wave acts as a lattice of evenly spaced potential energy wells for subwavelength-scale objects. Trapped particles interact with each other by exchanging waves that they scatter from the standing wave. Unless the particles have identical scattering properties, their wave-mediated interactions are nonreciprocal. Pairs of particles can use this nonreciprocity to harvest energy from the wave to sustain steady-state oscillations despite viscous drag and the absence of periodic driving. We show, in theory and experiment, that a minimal system composed of two acoustically levitated particles can access four distinct dynamical states, two of which are emergently active steady states. Under some circumstances, these emergently active steady states break spatiotemporal symmetry and therefore constitute a classical time crystal.

Landau quantization of two-dimensional free electrons and massless Dirac fermions plays a key role underlying many quantum phenomena in condensed matter physics. It usually requires the magnetic field, which arranges the charge carriers associated with the harmonic oscillation on a ladder of discrete Landau levels with a dissipationless edge state. Nevertheless, the presence of intrinsic dissipation and absence of a pseudomagnetic field in thermal diffusion precludes the observation of Landau quantization. Here, we report a recipe of creating a synthetic gauge serving as a pseudomagnetic field and achieve Landau quantization on real- and imaginary-valued spectra, on both of which complex pseudo-Landau levels are identified as isometric ladders. We experimentally observe the macroscopic quantum thermal Hall-like effect induced by dissipation, which is distinguished by a plateaulike effective thermal resistance. Our findings open up a unique paradigm for manipulating heat transfer and create an insightful platform for exploring dissipative non-Hermitian physics.

The majority of superconductors have more than one Fermi surface, on which the electrons pair below the critical temperature, yet their behavior can be well described by a single-band Bardeen-Cooper-Schrieffer theory. This is mostly due to interband scattering, especially in superconductors in the dirty limit, rigidly linking the pairing amplitude of the bands. This has limited experimental studies of the complex physics of multiband superconductivity. Here, we utilize the fact that elementary Pb—as a clean limit system—has two Fermi surfaces that are only weakly coupled by interband scattering, allowing the formation of two separate condensates. By studying stacking fault tetrahedra with a millikelvin scanning tunneling microscope, we show how to locally tune interband coupling ranging from weak to strong coupling and modify the superconducting order parameters from two well separated gaps to one merged gap around defects. The experiments critically test the theory of multiband superconductors and give a route to access a wide range of predicted quantum effects in these systems.

We introduce the concept of purely electronic chirality (PEC), which arises in the absence of structural chirality. In condensed matter physics and chemistry, chirality has conventionally been understood as a mirror-image asymmetry in crystal or molecular structures. We demonstrate that certain electronic orders exhibit chirality-related properties without atomic displacement. Specifically, we investigate quadrupole orders to realize such purely electronic chirality with handedness that can be tuned by magnetic fields. As a representative example, we analyze a model featuring 120° antiferro quadrupole orders on a distorted kagome lattice, predicting various chirality-related responses in the nonmagnetic ordered phase of URhSn. Furthermore, as a phonon analog, chiral phonons can emerge in achiral crystals through coupling with the PEC order. Our results provide a distinct origin of chirality and a fundamental basis for exploring the interplay between electronic and structural chirality.

We report a systematic and accurate approach for deriving the bulk free energy surface (FES), a function of temperature, polarization, and strain, from the first-principles density functional theory (DFT) of proper ferroelectrics. The core of our approach is the metadynamics algorithm that extracts the polarization dependence of the FES from all-atom molecular dynamics simulations without an a priori ansatz. The rest of the FES is derived from the metadynamics trajectories that span the relevant phase space. We demonstrate our approach in the case of lead titanate. The errors across the phase transition, due to DFT numerics, all-atom molecular dynamics, and free energy evaluation by enhanced sampling, can be systematically controlled and are of the order of $1\mathrm{meV}/\mathrm{atom}$. The accuracy of the resulting ab initio FES is only limited by the adopted functional approximation of DFT.

Magic numbers lie at the heart of nuclear structure, reflecting enhanced stability in nuclei with closed shells. While the emergence of magic numbers beyond 20 is commonly attributed to strong spin-orbit coupling, the microscopic origin of the spin-orbit potential remains elusive, owing to its dependence on the resolution scale and renormalization scheme of nuclear forces. Here, we investigate the evolution of nuclear shell structure with varying momentum resolution in nuclear interactions derived from chiral effective field theory, using the similarity renormalization group to link different scales. We uncover a novel transition from spin symmetry to pseudospin symmetry as the resolution scale decreases, during which magic numbers emerge naturally. A similar pattern is found in calculations using relativistic one-boson-exchange potentials, underscoring the robustness of the phenomenon. This establishes a direct connection between realistic nuclear forces with a high resolution scale and effective nuclear forces at coarse-grained scales, offering a first-principles explanation for the origin of magic numbers and pseudospin symmetry in nuclear shell structure and new insights into the structure of exotic nuclei far from stability.

Single-electron tunneling in mesoscopic superconducting islands has demonstrated a parity-modulated Coulomb blockade periodicity for decades. Yet, the quasiparticle dynamics mediating the interplay between Cooper-pair condensate coherence and charging energy remains poorly understood. Here, we uncover a new type of superconducting parity effect in a Coulomb blockade system comprising nano-sized Pb islands, investigated via low-temperature scanning tunneling spectroscopy. Our spectroscopic measurements demonstrate parity-dependent Coulomb gaps near the Fermi energy, associated with equidistant Coulomb peaks at higher energies. The parity dependence is distinct from the conventional even-odd Coulomb peak alternations and is validated through a parity transition of a Coulomb charge ring. As corroborated by theoretical simulations, we dub such intriguing phenomenon as the “dynamical” superconducting parity effect, which originates from an emergent tunneling channel facilitated by electron-hole conversion processes, dynamically coupled to Cooper-pair condensation. Our observations underscore the essential role of quasiparticle-mediated Cooper-pair formation in Coulomb blockade transport.

The ideal glass, a disordered system of particles with zero configurational entropy, cannot be realized through thermal processes. Nevertheless, we present a method for constructing ideal jammed packings of soft spheres, and thus the zero temperature ideal glass, in two dimensions. In line with the predicted properties, these critically jammed packings have high bulk and shear moduli as well as an anomalously high density. While the absence of pressure scaling in the shear moduli of crystalline materials is often attributed to the ordered nature of the particles, we show for the first time that disordered ideal packings also have this feature. We also find that the density of states avoids the low frequency power law scaling famously found in most amorphous materials, these configurations display hyperuniformity, and they melt at unusually high temperatures compared to conventional packings. In addition to resolving a long-standing mystery, this methodology represents a valuable shortcut in the generation of well-equilibrated glassy systems. The creation of such an ideal packing makes possible a complete exploration and explanation of two-dimensional jammed and glassy systems.

The binary black hole signal GW250114, the loudest gravitational wave detected to date, offers a unique opportunity to test Einstein’s general relativity (GR) in the high-velocity, strong-gravity regime and probe whether the remnant conforms to the Kerr metric. Upon perturbation, black holes emit a spectrum of damped sinusoids with specific, complex frequencies. Our analysis of the postmerger signal shows that at least two quasinormal modes are required to explain the data, with the most damped remaining statistically significant for about one cycle. We probe the remnant’s Kerr nature by constraining the spectroscopic pattern of the dominant quadrupolar ($\ell =m=2$) mode and its first overtone to match the Kerr prediction to tens of percent at multiple postpeak times. The measured mode amplitudes and phases agree with a numerical-relativity simulation having parameters close to GW250114. By fitting a parametrized waveform that incorporates the full inspiral-merger-ringdown sequence, we constrain the fundamental $(\ell =m=4)$ mode to tens of percent and bound the quadrupolar frequency to within a few percent of the GR prediction. We perform a suite of tests—spanning inspiral, merger, and ringdown—finding constraints that are comparable to, and in some cases 2–3 times more stringent than those obtained by combining dozens of events in the fourth Gravitational-Wave Transient Catalog. These results constitute the most stringent single-event verification of GR and the Kerr nature of black holes to date, and outline the power of black-hole spectroscopy for future gravitational-wave observations.

Graphene-based multilayer systems serve as versatile platforms for exploring the interplay between electron correlation and topology, thanks to distinctive low-energy bands marked by significant quantum metric and Berry curvature from graphene’s Dirac bands. Here, we investigate Mott physics and local spin moments in Dirac bands hybridized with a flat band of localized orbitals in functionalized graphene. Via hybridization control, a topological transition is realized between two symmetry-distinct site-selective Mott states featuring local moments in different Wyckoff positions, with a geometrically enforced metallic state emerging in between. We find that this geometrically controlled real-space switching of local moments and associated metal-insulator physics may be realized through proximity coupling of epitaxial graphene on SiC(0001) with group IV intercalants, where the Mott state faces geometrical obstruction in the large-hybridization limit. Our Letter shows that chemically functionalized graphene provides a correlated electron platform, very similar to the topological heavy fermions in graphene moiré systems but at significantly enhanced characteristic energy scales.

In an electronic system, spontaneous symmetry breaking can arise from many-body interaction between electrons, leading to degenerate ground states distinguishable by emergent effects otherwise prohibited by the symmetry. Here we show that ultrastrong coupling of a mesoscopic electronic system to the vacuum of a cavity resonator can lead to another paradigm of spontaneous breaking of spatial symmetries in both systems. As a pertinent example, we consider the orbital gyrotropic effects in a moiré superlattice embedded in a THz split ring cavity resonator. Our mean-field and exact diagonalization calculations consistently demonstrate a spontaneous parity symmetry breaking in both the electronic ground state and the cavity vacuum, leading to two degenerate hybrid ground states distinguished by their opposite orbital gyrotropic Hall and magnetic effects. These sizable responses in the cavity-embedded moiré superlattice are highly tunable by both the cavity field polarization and interlayer bias on the moiré superlattice, providing an advanced platform for manipulating gyrotropic effects.

On cooling through a temperature $T_S$ of around 324 K, ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ undergoes a transition from a semimetallic state to one with a gapped electronic spectrum that is suspected to be an excitonic insulator. However, at this transition the structure also changes, from orthorhombic to monoclinic, leaving open the question of whether it is driven primarily by excitonic ordering or by a lattice instability. A lattice instability of this symmetry would correspond to softening of a ${\mathrm{B}}_{2g}$ optical or acoustic phonon mode. Here, we report that elastocaloric measurements of ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ with induced ${\mathrm{B}}_{2g}$ strain reveal a thermodynamic susceptibility described by a Curie-Weiss law with a Curie temperature $T^{*}$ of 298 K. The fact that $T^{*}$ is close to $T_S$ rules out the possibility that the ${\mathrm{B}}_{2g}$ acoustic mode is responsible for the transition. Since prior Raman measurements have shown minimal softening of the ${\mathrm{B}}_{2g}$ optical mode as well, our finding strengthens the case that the transition is largely excitonic in nature. Our work underscores the potential of using strain as a tool for separating electronic and lattice contributions in phase transitions.

The absorption properties of ultrathin conductive films are of fundamental significance in electromagnetics and photonics, impacting applications from radar stealth to two-dimensional material optoelectronics. For decades, a 50% absorption limit has been considered intrinsic to such films in symmetric environments, regardless of frequency or incident angle. Here, we demonstrate the breaking of this long-standing limit under grazing incidence, where the absorption was regarded as negligible due to extreme impedance mismatch. We reveal a previously unknown absorption limit of $2\sqrt{2}-2\approx 82.8\%$ for grazing transverse-magnetic waves on arbitrarily thin, highly conductive films. This exceptional absorption arises from a pseudo-Brewster effect with minimal reflection $3-2\sqrt{2}\approx 17.2\%$ and vanishing skin depth of grazing waves. Remarkably, the enhanced absorption is sustained across an ultrabroad frequency range. Terahertz experiments using deep-subwavelength doped silicon wafers validate our theoretical predictions. These findings fundamentally advance our understanding of wave-matter interactions at deep-subwavelength scales and pave the way for extreme-angle photonic and electromagnetic devices.

Consider a fixed universe of $N=2^n$ elements and the uniform distribution over elements of some subset of size $K$. Given samples from this distribution, the task of complement sampling is to provide a sample from the complementary subset. We give a simple quantum algorithm that uses only a single quantum sample—a single copy of the uniform superposition over elements of the subset. When $K=N/2$, we show that the quantum algorithm succeeds with probability 1, whereas any classical algorithm that succeeds with bounded probability of error requires a number of samples of the order of $N$. This shows that in a sample-to-sample setting, quantum computation can achieve the largest possible separation over classical computation. We show that the same bound can be lifted to prove average-case hardness, paving the way for demonstrations on noisy intermediate-scale quantum (NISQ) computers. It follows that under the assumption of the existence of one-way functions, complement sampling gives provable, verifiable and NISQable quantum advantage in a sample complexity setting.

Millicharged particles are well-motivated dark matter candidates arising in many extensions of the standard model. We show that, despite their tiny coupling $e_m$ to photons, millicharged dark matter (mDM) in the Earth’s geomagnetic field can generate a quasistatic, monochromatic magnetic signal with angular frequency twice the mDM mass. Using null results from the SuperMAG and SNIPE Hunt collaborations, we constrain the effective charge of bosonic mDM in the mass range ${10}^{-18}-{10}^{-14}\mathrm{eV}$. The resulting upper bounds exceed stellar cooling constraints by over 13 orders of magnitude, demonstrating the power of this method.

Thermopower, through its entropic sensitivity, has recently emerged as a powerful probe of correlated states. Here, we report the first thermopower measurements of fractional quantum Hall (FQH) states in monolayer graphene, a system that can host new correlated states due to its relativistic dispersion relation. Our thermopower measurements reveal FQH states appearing in the $N=0$ and higher Landau levels, including new even denominator states. We employ temperature-dependent magneto-thermopower measurements to extract the energy gaps associated with the more prominent FQH states.

The gravitational wave signal produced by the merger of two compact objects includes both an oscillatory transient and a nonoscillatory part, the so-called memory effect. This produces a permanent displacement of test masses and has not yet been measured. We use general relativistic magnetohydrodynamic simulations, including neutrinos, with several representative viable equations of state, to quantify—for the first time—the effects of the neutron star magnetic field, neutrino emission, and the ejected mass on the linear and nonlinear displacement memory in binary neutron star mergers. We find that the additional contributions due to the emission of electromagnetic radiation, neutrinos and baryonic ejecta can be $\sim 15\%$ of the total memory for moderate magnetic fields and up to $\sim 50\%$ for extreme magnetic fields. The memory is most affected by changes in the equation of state, the binary mass, and the magnetic field. In particular, for moderate premerger field strengths, the dominant impact of the electromagnetic field is the change in the gravitational wave luminosity, and the associated gravitational wave null memory, due to the unstable growth of the magnetic field and the resulting redistribution of angular momentum it induces in the remnant. While the direct electromagnetic contribution to the null memory is additive, the change in the gravitational wave null memory can—in some cases—result in the total memory being smaller than that from the corresponding nonmagnetized binary. Furthermore, in contrast to binary black hole mergers, the growth of the memory in binary neutron star mergers is extended due to the long emission timescale of electromagnetic fields, neutrinos, and ejecta. These results necessitate the consideration of the magnetic field, as well as the equation of state, for accurate parameter estimation in future analyses of gravitational wave memory data.