Probing the quantum geometry and topology in condensed matter systems has relied heavily on static electronic transport experiments in magnetic fields. Yet, contact-free optical measurements have rarely been explored. Here, we report the observation of resonant magnetic circular dichroism (MCD) in the infrared range in thin film ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$ exhibiting a spectral intensity that correlates with the anomalous Hall effect. Both phenomena emerge with a field-driven phase transition from an antiferromagnet to a canted ferromagnet. By theoretically relating the MCD to the anomalous Hall effect via Berry curvature for a metallic state, we show that this transition accompanies an abrupt onset of Berry curvature, signaling a topological phase transition from a topological insulator to a doped Chern insulator. Our density functional theory calculation suggests the MCD signal mainly originates from an optical transition at the Brillouin zone edge, hinting at a potential new source of Berry curvature away from the commonly considered $\mathbf{\Gamma }$ point. Our findings demonstrate a novel experimental approach for detecting Berry curvature through spectroscopy of the interband MCD, generally applicable to magnetic materials.

Vortex states of photons, electrons, and other particles are freely propagating wave packets with helicoidal wave fronts winding around the axis of a phase vortex. A particle prepared in a vortex state carries a nonzero orbital angular momentum projection on the propagation direction, a quantum number that has never been exploited in experimental particle and nuclear physics. Low-energy vortex photons, electrons, neutrons, and helium atoms have been demonstrated in experiment and found numerous applications, and there exist proposals of boosting them to higher energies. However, verification that a high-energy particle is indeed in a vortex state will be a major challenge, since the low energy techniques become impractical at higher energies. Here, we propose a new diagnostic method based on the so-called superkick effect, which can unambiguously detect the presence of a phase vortex. A proof-of-principle experiment with vortex electrons can be done with existing technology, and its realization will also constitute the first observation of the superkick effect.

Materials that are constantly driven out of thermodynamic equilibrium, such as active and living systems, typically violate the Einstein relation. This may arise from active contributions to particle fluctuations which are unrelated to the dissipative resistance of the surrounding medium. We show that in these cases the widely used relation between informatic entropy production and heat dissipation does not hold. Consequently, fluctuation relations for the mechanical work, such as the Jarzynski and Crooks theorems, are invalid. We relate the breaking of the correspondence between entropy production and heat dissipation to departure from the fluctuation-dissipation theorem. We propose a temperaturelike variable that restores this correspondence and gives rise to a generalized second law of thermodynamics, whereby the dissipated heat is necessarily non-negative and vanishes at equilibrium. The Clausius inequality, Carnot maximum efficiency theorem, and relation between the extractable work and the change of free energy are recovered as well.

Calculations of the two-loop electron self-energy for the $1S$ Lamb shift are reported, performed to all orders in the nuclear binding strength parameter $Z\alpha$ (where $Z$ is the nuclear charge number and $\alpha$ is the fine structure constant). Our approach allows calculations to be extended to nuclear charges lower than previously possible and improves the numerical accuracy by more than an order of magnitude. Extrapolation of our all-order results to hydrogen yields a result twice as precise as the previously accepted value [E. Tiesinga et al. Rev. Mod. Phys. 93, 025010 (2021)], differing from it by 2.8 standard deviations. The resulting shift in the theoretical prediction for the $1S\text{−}2S$ transition frequency in hydrogen decreases the value of the Rydberg constant by one standard deviation.

Recently, robust $d$-wave superconductive (SC) order has been unveiled in the ground state of the 2D $t-t^{\prime }-J$ model—with both nearest-neighbor ($t$) and next-nearest-neighbor ($t^{\prime }$) hoppings—by density matrix renormalization group studies. However, there is currently a debate on whether the $d$-wave SC holds up strong on both $t^{\prime }/t>0$ and $t^{\prime }/t<0$ cases for the $t-t^{\prime }-J$ model, which correspond to the electron- and hole-doped sides of the cuprate phase diagram, respectively. Here, we exploit state-of-the-art thermal tensor network approach to accurately obtain the phase diagram of the $t-t^{\prime }-J$ model on cylinders with widths up to $W=6$ and down to low temperature as $T/J\simeq 0.06$, pushing the boundaries of contemporary finite-$T$ calculations. For $t^{\prime }/t>0$, we find a domelike SC regime with a diverging $d$-wave pairing susceptibility, ${\chi }_{\mathrm{SC}}\propto 1/T^{\alpha }$ below a characteristic temperature $T_c^{*}$. Near optimal doping, $T_c^{*}$ reaches its highest value of about $0.15J$. Above $T_c^{*}$ yet below a higher crossover temperature $T^{*}$, the magnetic susceptibility becomes suppressed, which can be related to the onset of pseudogap (PG) behaviors. On the other hand, for $t^{\prime }/t<0$, we find the pairing correlations are much weaker, although there exhibits a node-antinode structure in the PG regime as observed in the hole-doped cuprates. The thermal tensor network calculations of the $t-t^{\prime }-J$ model underscore both the similarities and differences in the finite-temperature phase diagram between the fundamental model and cuprates, yielding unique insights into their intricate behaviors.

Water electrolysis suffers from electron transfer barriers during oxygen evolution reactions, which are spin-related for magnetic materials. Here, the electron transfer at the ${\mathrm{Fe}}_{64}{\mathrm{Ni}}_{36}\text{−}{\mathrm{FeNiO}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}$ interface is effectively accelerated when the electrode is heated to trigger the Invar effect in ${\mathrm{Fe}}_{64}{\mathrm{Ni}}_{36}$ Invar alloy, providing more unoccupied orbitals as electron transfer channels without pairing energy. As a result of thermally stimulated changes in electronic states, ${\mathrm{Fe}}_{64}{\mathrm{Ni}}_{36}/{\mathrm{FeNiO}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}$ achieved a cascaded oxidation of the catalytic center and water. Unlike direct modifications made by varying compositions and synthesis, regulating electronic states by energy field opens a new avenue to discover materials with energy coupling effects.

Studying the properties and phase diagram of iron at high-pressure and high-temperature conditions has relevant implications for Earth’s inner structure and dynamics and the temperature of the inner core boundary (ICB) at 330 GPa. Also, a hexagonal-closed packed to body-centered cubic (bcc) phase transition has been predicted by many theoretical works but observed only in a few experiments. The recent coupling of high-power laser with advanced x-ray sources from synchrotrons allows for novel approaches to address these issues. Here, we present a study on shock compressed iron up to 270 GPa and 5800 K probed by single-pulse (100 ps FWHM) x-ray absorption spectroscopy (XAS). Based on the analysis of the XAS spectra, we provide structural identification and bulk temperature measurements along the Hugoniot up to the melting. These results rule out the predicted transition to a high-temperature bcc phase and allow one to discriminate among existing equations of state models and melting curves. In particular, we report the first bulk temperature measurement in shock compressed iron on the melting plateau at 240(20) GPa and 5345(600) K. The melting curve resulting from our work extrapolates to a temperature of 6202(514) K at 330 GPa and represents a refined upper bound for the ICB temperature.

We measure the high-intensity laser propagation throughout meter-scale, channel-guided laser-plasma accelerators by adjusting the length of the plasma channel on a shot-by-shot basis, showing high-quality guiding of 500 TW laser pulses over 30 cm in a hydrogen plasma of density $n_0\approx 1\times {10}^{17}{\mathrm{cm}}^{-3}$. We observed transverse energy transport of higher-order modes in the first $\approx 12\mathrm{cm}$ of the plasma channel, followed by quasimatched propagation, and the gradual, dark-current-free depletion of laser energy to the wake. We quantify the laser-to-wake transfer efficiency limitations of currently available petawatt-class lasers and demonstrate via simulation how control over the laser mode can significantly improve beam parameters. Using 21.3 J of laser energy, and triggering localized electron injection, we observed electron bunches with single, quasimonoenergetic peaks up to 9.2 GeV with charge extending beyond 10 GeV.

The existence of light QCD axions, whose mass depends on an additional free parameter, can lead to a new ground state of matter, where the sourced axion field reduces the nucleon effective mass. The presence of the axion field has structural consequences, in particular, it results in a thinner (or even prevents its existence) heat-blanketing envelope, significantly altering the cooling patterns of neutron stars. We exploit the anomalous cooling behavior to constrain previously uncharted regions of the axion parameter space by comparing model predictions with existing data from isolated neutron stars. Notably, this analysis does not require the light QCD axion to be the dark matter candidate.

Based on its simple valence electron configuration, we may expect lithium to have straightforward physical properties that are easily explained. However, solid lithium, when cooled below 77 K, develops a complex structure that has been debated for decades. A close parallel is found in sodium below 36 K where the crystal structure still remains unresolved. In this Letter, we explore a possible driving force behind this complexity. We begin with the observation that Li and Na form close-packed structures at low temperatures. We demonstrate a gauge symmetry that forces all close-packed structures to have the same electronic energy and, in fact, the very same band structure. This symmetry requires two conditions: (a) bands must arise from $s$ orbitals, and (b) hoppings beyond second-nearest neighbors must be negligible. We argue that both can be reasonably invoked in Li and Na. When these conditions are satisfied, we have extensive degeneracy with the number of competing isoenergetic structures growing exponentially with system size. Weak effects, such as $p$-orbital admixture, long-range hopping, and phonon zero-point energy, can break this symmetry. These can play a decisive role in “selecting” one particular ordered structure. This point of view may explain the occurrence of ordered structures in Li and Na under pressure. Our results suggest that martensitic transitions may also occur in heavier alkali metals such as potassium.

We realize a Laughlin state of two rapidly rotating fermionic atoms in an optical tweezer. By utilizing a single atom and spin resolved imaging technique, we sample the Laughlin wave function thereby revealing its distinctive features, including a vortex distribution in the relative motion, correlations in the particles’ relative angle, and suppression of the interparticle interactions. Our Letter lays the foundation for atom-by-atom assembly of fractional quantum Hall states in rotating atomic gases.

Motivated by the similarity of the mathematical structure of Einstein’s general relativity in its weak field limit and of Maxwell’s theory of electrodynamics it is shown that there are gravitational analogs of the Josephson effect and the quantum Hall effect. These effects can be combined to derive a gravitational analogue of the electric quantum metrological triangle. The gravitational quantum metrological triangle may have applications in metrology and could be used to investigate the relation of the Planck constant to fundamental particle masses. This allows for quantum tests of the weak equivalence principle. Moreover, the similarity of the gravitational and the electric quantum metrological triangle can be used to test the universality of quantum mechanics.

Two-dimensional (2D) materials that exhibit spontaneous magnetization, polarization, or strain (referred to as ferroics) have the potential to revolutionize nanotechnology by enhancing the multifunctionality of nanoscale devices. However, multiferroic order is difficult to achieve, requiring complicated coupling between electron and spin degrees of freedom. We propose a universal method to engineer multiferroics from van der Waals magnets by taking advantage of the fact that changing the stacking between 2D layers can break inversion symmetry, resulting in ferroelectricity as well as magnetoelectric coupling. We illustrate this concept using first-principles calculations in bilayer ${\mathrm{NiI}}_2$, which can be made ferroelectric upon rotating two adjacent layers by 180° with respect to the bulk stacking. Furthermore, we discover a novel strong magnetoelectric coupling between the interlayer spin order and interfacial electronic polarization. Our approach is not only general but also systematic and can enable the discovery of a wide variety of 2D multiferroics with strong magnetoelectric coupling.

Knitted fabrics are metamaterials with remarkable mechanical properties, such as extreme deformability and multiple history-dependent rest shapes. This Letter shows that those properties may stem from a continuous set of metastable states for a fabric free of external forces. This is evidenced through experiments, numerical simulations, and analytical developments. Those states arise from the frictional contact forces acting in the braid zone where the threads interlace and follow a line in the configuration space accurately described by a 2D-elastica model. The friction coefficient sets a terminal point along this line, and the continuous set of metastable states is obtained by varying the braid inclination while contact forces remain on the friction cone.

Influenza A viruses (IAVs) must navigate through a dense extracellular mucus to infect airway epithelial cells. The mucous layer, composed of glycosylated biopolymers (mucins), presents sialic acid that binds to ligands on the viral envelope and can be irreversibly cleaved by viral enzymes. It was recently discovered that filamentous IAVs exhibit directed persistent motion along their long axis on sialic acid-coated surfaces. This Letter demonstrates through stochastic simulations and mean-field theory, how IAVs harness a “burnt-bridge” Brownian ratchet mechanism for directed persistent translational motion. Importantly, our analysis reveals that equilibrium features of the system primarily control the dynamics, even out of equilibrium, and that asymmetric distribution of ligands on the virus allows for more robust directed transport. We show viruses occupy the optimal parameter range (“Goldilocks zone”) for efficient mucous transport, possibly due to the evolutionary adaptation of enzyme kinetics. Our findings suggest novel therapeutic targets and provide insight into possible mechanisms of zoonotic transmission.

Bilayers of two-dimensional van der Waals materials that lack an inversion center can show a novel form of ferroelectricity, where certain stacking arrangements of the two layers lead to an interlayer polarization. Under an external out-of-plane electric field, a relative sliding between the two layers can occur, accompanied by an interlayer charge transfer and a ferroelectric switching. We show that the domain walls that mediate ferroelectric switching are a locus of strong attractive interactions between electrons. The attraction is mediated by the ferroelectric domain wall fluctuations, effectively driven by the soft interlayer shear phonon. We comment on the possible relevance of this attraction mechanism to the recent observation of an interplay between sliding ferroelectricity and superconductivity in bilayer ${\mathrm{T}}_d\text{−}{\text{MoTe}}_2$. We also discuss the possible role of this mechanism in the superconductivity of moiré bilayers.

Measuring bipartite fluctuations of a conserved charge, such as the particle number, is a powerful approach to understanding quantum systems. When the measured region has sharp corners, the bipartite fluctuation receives an additional contribution known to exhibit a universal angle dependence in 2D isotropic and uniform systems. Here we establish that, for generic lattice systems of interacting particles, the corner charge fluctuation is directly related to quantum geometry. We first provide a practical scheme to isolate the corner contribution on lattices and analytically prove that its angle dependence in the “small-angle limit” measures exclusively the integrated quantum metric. A model of a compact obstructed atomic insulator is introduced to illustrate this effect analytically, while numerical verification for various Chern insulator models further demonstrate the experimental relevance of the corner charge fluctuation in a finite-size quantum simulator as a probe of quantum geometry. Last but not least, for free fermions, we unveil an intimate connection between quantum geometry and quantum information through the lens of corner entanglement entropies.

The morphology and kinetics of the crystal growth front have been poorly explored at the particle level. Here, we experimentally observe the crystal growth front in liquid with single-particle kinetics using colloid systems and reveal a surface layer of polymorphic crystal near the solid–solid transition when the two crystals form a low-energy coherent interface. The thickness of the surface crystal can exceed 50 particles and grows logarithmically with the temperature as approaching the solid–solid transition which follows premelting theory. The liquid–crystal interface grows continuously through random attachments of diffusive particles, while the crystal–crystal interface exhibits a martensitic growth with collective motions. The presence of a surface crystalline layer reduces defect density, which is helpful in crystal fabrication.

We study a mixture of extensile and contractile cells using a vertex model extended to include active nematic stresses. The two cell populations phase separate over time. While phase separation strengthens monotonically with an increasing magnitude of contractile activity, the dependence on extensile activity is nonmonotonic, so that sufficiently high values reduce the extent of sorting. We interpret this by showing that extensile activity renders the system motile, enabling cells to undergo neighbor exchanges. Contractile cells that come into contact as a result are then more likely to stay connected due to an effective attraction arising from contractile activity.

Detection and attribution (DA) studies are cornerstones of climate science, providing crucial evidence for policy decisions. Their goal is to link observed climate change patterns to anthropogenic and natural drivers via the optimal fingerprinting method (OFM). We show that response theory for nonequilibrium systems offers the physical and dynamical basis for OFM, including the concept of causality used for attribution. Our framework clarifies the method’s assumptions, advantages, and potential weaknesses. We use our theory to perform DA for prototypical climate change experiments performed on an energy balance model and on a low-resolution coupled climate model. We also explain the underpinnings of degenerate fingerprinting, which offers early warning indicators for tipping points. Finally, we extend the OFM to the nonlinear response regime. Our analysis shows that OFM has broad applicability across diverse stochastic systems influenced by time-dependent forcings, with potential relevance to ecosystems, quantitative social sciences, and finance, among others.