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.

Dissipative Kerr solitons in optical microresonators offer unparalleled platforms for ultralow-noise, high-repetition rate frequency comb generation with a compact form and driven by a continuous-wave laser. However, despite their attractive properties suited for practical applications, fundamental limitations regarding their output power and conversion efficiency still remain crucial problems that must be overcome. Here we discover unexplored operation regimes of Kerr soliton microcombs yielding high power and a picosecond pulse width by exploiting the strong mode interaction in birefringent crystalline microresonators. We demonstrate experimentally single-soliton microcombs with average powers of up to 24 and 38 mW as well as an improved conversion efficiency with a double-digit percentage and a microwave soliton repetition rate as low as 15.5 GHz. The observations are in agreement with numerical analyses based on the Lugiato-Lefever equation. The presented results not only facilitate novel applications and an architecture based on microresonator frequency combs, but also contribute to a further understanding of soliton physics.

Combination of optical spectroscopy and in situ high-temperature–high-pressure techniques, were employed to investigate the melting curve and map out the location of methane’s solid phases up to 45 GPa and 1100 K. The experiments yield two distinct diagrams, one that demonstrates the kinetic phase transformations and the other presenting the equilibrium states usually reached with time. Raman spectroscopy demonstrates that the appearance and transitions between the higher pressure phases (VII, VIII, and IX) are strongly dependent on the pressure-temperature-time path. Combined visual observations and Raman spectroscopy indicate that the melting curve of methane extends to significantly higher temperatures than previously reported, e.g., $\sim 1000\mathrm{K}$ at 15 GPa. The study also suggests that some inconsistencies in the earlier melting data could be attributed to photochemical dissociation and/or a reaction induced by high-intensity light sources.

Metamaterials are a promising platform for a range of applications, from shock absorption to mechanical computing. These functionalities typically rely on floppy modes or mechanically frustrated loops, both of which are difficult to design. In particular, how to design multiple modes or loops with target deformations remains an open problem. We introduce a combinatorial approach that allows to create an arbitrarily large number of floppy modes and frustrated loops. The design freedom of the mode shapes enables to easily introduce kinematic incompatibility to turn them into frustrated loops. We demonstrate that floppy modes can be sequentially buckled by using a specific instance of elastoplastic buckling. We utilize our combinatorial floppy chains and frustrated loops to achieve matrix-vector multiplication in materia. Our findings bring about new principles for the design and use of floppiness and frustration in soft matter and metamaterials.

Anisotropic flow and radial flow are two key probes of the expansion dynamics and properties of the quark-gluon plasma (QGP). While anisotropic flow has been extensively studied, radial flow, which governs the system’s radial expansion, has received less attention. Notably, direct experimental evidence for the global and collective nature of radial flow fluctuations has been lacking. This Letter presents the first measurement of transverse momentum ($p_{\mathrm{T}}$) dependence of radial flow fluctuations ($v_0(p_{\mathrm{T}})$) over $0.5<p_{\mathrm{T}}<10\mathrm{GeV}$ and demonstrates its collective nature using a two-particle correlation method in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The data reveal three key features supporting the collective nature of radial flow: long-range correlation in pseudorapidity, factorization in $p_{\mathrm{T}}$, and centrality-independent shape in $p_{\mathrm{T}}$. The comparison with a hydrodynamic model demonstrates the sensitivity of $v_0(p_{\mathrm{T}})$ to bulk viscosity, a crucial transport property of the QGP. These findings establish a new, powerful tool for probing collective dynamics and properties of the QGP.

This Letter presents measurements of long-range transverse-momentum correlations using a new observable, $v_0(p_{\mathrm{T}})$, serving as a probe of event-by-event radial-flow fluctuations, the underlying radial expansion, and the medium’s properties in heavy-ion collisions. Results are reported for inclusive charged particles, pions, kaons, and protons across various centrality intervals in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, recorded by the ALICE detector. A pseudorapidity-gap technique, similar to that used in anisotropic-flow studies, is employed to suppress short-range correlations. At low $p_{\mathrm{T}}$, a characteristic mass ordering consistent with hydrodynamic collective flow is observed. At higher $p_{\mathrm{T}}$ ($>3\mathrm{GeV}/c$), protons exhibit larger $v_0(p_{\mathrm{T}})$ than pions and kaons, in agreement with expectations from quark-recombination models. Comparisons to viscous hydrodynamic calculations with varying bulk viscosity and equation of state demonstrate the sensitivity of the $v_0(p_{\mathrm{T}})$ observable to these key medium properties. The findings establish $v_0(p_{\mathrm{T}})$ as a valuable addition to the set of observables used in Bayesian analyses for extracting the transport properties and constraining the equation of state of strongly interacting matter, while also helping to systematically explore its sensitivity and impact within such global studies.

The $2{{}^3\mathrm{S}}_1\to 2{}^3{\mathrm{P}}_2$ interval (${\nu }_2$) in positronium has been measured using a phase-variation separated oscillatory fields technique. A beam of positronium atoms in the $2{}^3{\mathrm{S}}_1$ state was passed through two spatially separated coherent microwave fields tuned close to the ${\nu }_2$ resonance frequency ($8626.71\pm 0.08\mathrm{MHz}$), and the surviving beam fraction was recorded as a function of the relative phase between the fields. The resonance frequency was obtained from the frequency dependence of the phase of the interference signal without scanning over the full spectral line shape of the transition. We obtain ${\nu }_2=8626.39\pm 1.17_{\mathrm{stat}}\pm 0.80_{\mathrm{sys}}\mathrm{MHz}$, which is in agreement with QED theory.

We experimentally demonstrate that the rotation of molecules embedded in helium nanodroplets can be controlled with an optical centrifuge, allowing for the study of molecular dynamics inside the strongly interacting many-body environment of superfluid helium at variable levels of rotational excitation. By doping the droplets with dimers of nitric oxide, $(\mathrm{NO}{)}_2$, and measuring the degree of their centrifuge-induced alignment as a function of time, we show both the forced in-field rotation of molecules in a continuous range of frequencies, as well as the field-free resonant rotation with a long nanosecond-scale decay. The ability to control and monitor the rotational dynamics of molecular rotors inside the superfluid medium may shed new light on superfluidity and the interaction of superfluids with defects at the atomic level.

We numerically construct asymptotically global ${\mathrm{AdS}}_3\times {\mathrm{S}}^3\times {\mathrm{T}}^4$ black holes in type IIB supergravity, with ${\mathbb{R}}_t\times \mathrm{SO}(2)\times \mathrm{SO}(3)\times \mathrm{U}(1{)}^4$ symmetry, localized on the ${\mathrm{S}}^3$ and translationally invariant along the torus. These solutions, with horizons whose spatial cross sections have ${\mathrm{S}}^4\times {\mathrm{T}}^4$ topology, dominate the microcanonical ensemble at low energies. At higher energies, a first-order phase transition occurs to $\mathrm{BTZ}\times {\mathrm{S}}^3\times {\mathrm{T}}^4$ black holes—possessing ${\mathbb{R}}_t\times \mathrm{SO}(2)\times \mathrm{SO}(4)\times \mathrm{U}(1{)}^4$ symmetry and ${\mathrm{S}}^1\times {\mathrm{S}}^3\times {\mathrm{T}}^4$ horizon topology. By the AdS/CFT correspondence, this transition reflects the spontaneous breaking of the SO(4) $R$ symmetry of the $D1\text{−}D5$ ${\mathrm{CFT}}_2$ to SO(3). We also compute the expectation value of the scalar operator with lowest conformal dimension in the low-energy phase. Our SO(3)-localized black holes—together with the $\mathrm{U}(1{)}^2$-localized solutions of Bena et al. [J. High Energy Phys. 10 (2025) 165.]—point to a rich landscape of novel black holes that may approach the ${\mathrm{CFT}}_2$ “sparseness bootstrap condition,” and shed light on how macroscopic entanglement in thermal phases encodes microscopic structure via internal directions.

We provide evidence that three-party entanglement signals in holography obey a relation that is not satisfied by generalized Greenberger-Horne-Zeilinger (GHZ) states. Using proposed holographic duals for these entanglement signals, we provide a geometric argument establishing this relation. This is the first known inequality on the structure of pure three-party holographic states, and shows that time-symmetric holographic states can never have purely GHZ-like entanglement. We also discuss similar relations for four parties.

Developments in ultrastable lasers have fueled remarkable advances in optical frequency metrology and quantum science. A key ingredient in further improving laser frequency stability is the use of low-noise mirror materials such as AlGaAs crystalline coatings. However, excess noise observed with these coatings limits the performance of cryogenic silicon cavities with AlGaAs mirrors to similar levels achieved with conventional dielectric coatings. With a new pair of crystalline coated mirrors in a 6-cm-long cryogenic silicon cavity operated at 17 K, we demonstrate a clear advantage of crystalline coatings over dielectric coatings. The achieved fractional frequency stability of $2.5\times {10}^{-17}$ at 10 s is four times better than expected for dielectric mirrors and corresponds to more than a tenfold reduction in the coating mechanical loss factor. We also combine two silicon cavities to demonstrate optical frequency averaging for enhanced stability. In addition, we present a long-term frequency drift record of four cryogenic silicon cavities measured over several years. These results open up realistic prospects for cavity-stabilized lasers with ${10}^{-18}$ fractional stability, as well as an all-optical timescale with continuously operating optical local oscillators.