We compute medium corrections to the energy-energy correlator (EEC) for jets in electron-nucleus collisions at leading order in the QCD coupling and the interaction of the jet with the medium. We derive an analytical expression for the modification of the EEC as a function of the opening angle and show that the modification is strongest at large angles within the jet cone. We obtain explicit results for the dependence of the modification on the jet energy, the scattering power of cold nuclear matter, and the path length within the medium. We extend our calculations to gluon jets in proton-nucleus collisions and compare our results with recent preliminary data for proton-lead collisions at the LHC. We also discuss the role of comovers on the EEC in $\mathrm{p}+\mathrm{Pb}$ collisions.

We predict the generation of ultraflat broadband soliton microcombs in a driven quadratic-Kerr nonlinear microring resonator via phase-matched second-harmonic generation. The unprecedented spectral flatness arises from a novel cavity mechanism of symmetric dispersive wave generation, enabled by opposite group-velocity dispersions—anomalous at the fundamental frequency and normal at the second harmonic—without requiring higher-order dispersion engineering. This mechanism manifests itself as a characteristic long-rippled-wing bright soliton at the second harmonic, thereby generating the ultraflat spectrum. We develop analytical criteria for predicting the radiated frequencies, and show that, under proper control of relative cavity losses, the resulting combs exhibit nearly vanishing ($\sim 0\mathrm{dB}$) comb-line power variations over a broad spectral range, at variance with platicon microcombs that operate at normal dispersions. Our results offer a pathway to realize octave-spanning, highly efficient, coherent ultraflat combs without needing external phase or intensity modulators, enabling applications such as high-capacity telecommunications, precision metrology, and astrophysical spectrograph calibration.

Breaking spatial symmetries can induce interactions between disparate physical fields, which manifest in the macroscopic properties of materials as cross-coupling terms. Prominent examples include Willis terms in phononics and bianisotropic terms in photonics. However, the development of analogous cross-couplings in heat conduction remains limited and incomplete; here, we close this knowledge gap. To this end, we introduce an exact and universal homogenization method to capture the macroscopic dynamics of various physical processes in heterogeneous media. For heat conduction and thermodynamics, the method shows that thermal bianisotropy emerges through the intentional design of spatial asymmetry. In certain conditions, the resulting macroscopic description is free from the infinite heat speed paradox inherent in Fourier’s law of conduction. We support the exact theory with examples based on heuristic homogenization of a canonical scattering problem. These results may benefit the design of thermal metamaterials with asymmetric response.

Monolayer ${\mathrm{In}}_2\mathrm{Se}3$ exhibits unexpected in-plane polarization, despite having $C_{3v}$ symmetry, a feature that was traditionally considered forbidden by symmetry. To explain this remarkable behavior, Ji et al. proposed the concept of fractional quantum ferroelectricity (FQFE), in which polarization occurs in fractional multiples of a quantum, and argued that this phenomenon violates the conventional Neumann’s principle. In this Letter, we introduce a generalized form of Neumann’s principle and demonstrate that both FQFE and conventional ferroelectricity can be consistently described within this unified theoretical framework. We propose a method, based on the generalized Neumann’s principle, for the systematic identification of FQFE materials. This approach is straightforward to apply and offers a clear conceptual understanding and deep physical insight for FQFE. Using this method, we determine all symmetry-allowed FQFE cases across the 32 crystallographic point groups. Since practical applications rely on the ability to control polarization, we further show that FQFE can be effectively switched via coupling with conventional polarization. Using ${\mathrm{HfZnN}}_2$ as an illustrative example, we reveal the underlying mechanism of this coupling and outline a strategy to identify other materials with similar switching behavior.

We study the interplay between quantum geometry, interactions, and external fields in complex band systems. When Wannier obstructions preclude a description based solely on atomiclike orbitals, this complicates the prediction of electromagnetic responses, particularly in the presence of disorder and interactions. In this Letter, we introduce a generalized Peierls substitution framework based on Lagrange multipliers to enforce the constraints of the Wannier obstruction in the band of interest. Thus, we obtain effective descriptions of interactions and disorder in the presence of nontrivial quantum geometry of that band. We apply our approach to examples including the diamagnetic response in flat-band superconductors and delocalization effects in flat-band metals caused by interactions and disorder.

We study laser-induced ultrafast magnetization reversal in a ferromagnetic spin valve by comparing the effects of direct laser excitation and ultrashort hot-electron pulses. A wedged Cu layer is deposited atop the spin valve to tune energy transmission to the magnetic stack for both optical and hot-electron excitation. We demonstrate single-shot magnetization reversal of the free layer using hot-electron pulses. Moreover, such reversal is achieved even with picosecond laser pulses. The influence of laser fluence, Cu thickness ($t_{\mathrm{Cu}}$), and pulse duration is investigated in detail. Our results indicate that the key factor enabling magnetization reversal is full demagnetization of the free layer, driven by a rapid rise in its electronic temperature—achieved via either direct laser or hot-electron excitation. This work advances the understanding of ultrafast magnetization reversal via nonlocal heat and spin transport under strongly out-of-equilibrium conditions.

We experimentally investigate the drag force exerted by a suspension of light-induced active particles (APs) on a translating and beating idealized flagellum-shaped object realized through negative phototactic interactions with the APs. We observe both positive and negative drag forces, depending on the beating frequency and translational velocity, driven by the dynamic redistribution of APs in response to the object’s motion. These findings are supported by numerical simulations and an analytical model, extendable to a range of slender geometries. Our results illustrate the complex interplay between geometric body changes and the density distribution in active baths, which may also be relevant for microrobotic applications.

Cosmological gravitational-wave backgrounds are an exciting science target for next-generation ground-based detectors, as they encode invaluable information about the primordial Universe. However, any such background is expected to be obscured by the astrophysical foreground from compact-binary coalescences. We propose a novel framework to detect a cosmological gravitational-wave background in the presence of binary black holes and binary neutron star signals with next-generation ground-based detectors, including Cosmic Explorer and the Einstein Telescope. Our procedure involves first removing all the individually resolved binary black hole signals by notching them out in the time-frequency domain. Then, we perform joint Bayesian inference on the individually resolved binary neutron star signals, the unresolved binary neutron star foreground, and the cosmological background. For a flat cosmological background, we find that we can claim detection at $5\sigma$ level when ${\mathrm{\Omega }}_{\mathrm{ref}}\ge 2.7\times {10}^{-12}/\sqrt{T_{\mathrm{obs}}/\mathrm{yr}}$, where $T_{\mathrm{obs}}$ is the observation time (in years), which is within a factor of $\lesssim 2$ from the sensitivity reached in the absence of these astrophysical foregrounds.

Exploring new Hall effect is always a fascinating research topic. The ordinary Hall effect and the quantum Hall effect, initially discovered in two-dimensional (2D) nonmagnetic systems, are the phenomena that a transverse current is generated when a system carrying an electron current is placed in a magnetic field perpendicular to the currents. In this Letter, we propose the electric counterparts of these two Hall effects, termed the “electric Hall effect” (EHE) and the “quantum electric Hall effect” (QEHE). The EHE and QEHE emerge in 2D magnetic systems, where the transverse current is generated by applying an electric gate field instead of a magnetic field. We present a symmetry requirement for both intrinsic EHE and QEHE. Besides, we establish an analytical expression for the intrinsic EHE coefficient when the gate field is weak. We show that it is determined by two band geometric quantities: Berry curvature polarization and Berry curvature polarizability. Via first-principles calculations, we investigate the EHE in the monolayer $\mathrm{Ca}{(\mathrm{FeN})}_2$, where significant EHE coefficient is observed around band crossings. Furthermore, we demonstrate that the QEHE can appear in the semiconductor monolayer $\mathrm{BaM}{\mathrm{n}}_2{\mathrm{S}}_3$, of which the Hall conductivity exhibits steps that take on the quantized values 0 and $\pm 1$ in the unit of $e^2/h$ by varying the gate field within the experimentally achievable range. Because of the great tunability of the electric gate field, the EHE and QEHE proposed here can be easily controlled, and should have significant potential applications.

We study the charge transport across a band-tuned metal-insulator transition in two dimensions. For high temperatures $T$ and chemical potentials $\mu$ far from the transition point, conduction is ballistic and the resistance $R(T)$ verifies a simple one-parameter scaling relation. Here, we explore the limits of this semiclassical behavior and study the quantum regime beyond, where scaling breaks down. We analytically evaluate the simplest Feynman diagram of the linear-response conductivity $\sigma =1/R$ of a parabolic band endowed with a finite lifetime. Our formula shows excellent agreement for experiments for a field-tuned ${\mathrm{MoTe}}_2/{\text{WSe}}_2$ moiré bilayer, and can capture the quantum effects responsible for breaking the one-parameter scaling. We go on to discuss a fascinating prediction of our model: The resistance at the quantum-critical band-tuned Lifshitz point ($\mu =T=0$) has the universal value, $R_L=(2\pi h)/e^2$, per degree of freedom, in congruence with experiment. Furthermore, we investigate whether two-dimensional metal-insulator transitions driven by strong electron correlations or disorder can also be classified by their quantum-critical resistance and come up with an, in principle, complete assignment of the transition mechanism.

Antiferromagnetic states which break inversion symmetry are able to host odd-parity spin splittings, in analogy to altermagnets. Here we study the emergence of these inversion-asymmetric antiferromagnet (IA AFM) states via an itinerant mechanism in nonsymmorphic systems with two magnetic ions per unit cell. We identify the symmetries that allow mixed-parity irreducible representations for commensurate ordering vectors, and hence permit a continuous transition into the IA AFM. The Landau free energy which describes the transition is derived from a general microscopic model, from which we establish conditions favorable to the appearance of the IA AFM: inversion is not a site symmetry of a magnetic ion, and the nesting involves different bands. Moreover, the odd-parity spin splitting is negatively correlated with the stability of the IA AFM. We illustrate our conclusions with specific examples. The insight into the IA AFM provided by our work can guide the identification of candidate materials.

We study the entanglement properties of two-mode bosonic Gaussian states based on their multi-mode counting statistics. We exploit the idea that measuring high-order correlations of particle numbers can reveal entanglement without making any assumptions about the coherence of the fields. We show that the two- and four-body number correlations are sufficient to fully characterize the entanglement of two-mode bosonic Gaussian states for which each mode exhibits a thermal distribution. In addition, we derive an entanglement witness based on two-body correlations alone. Our findings are of great importance because it becomes possible to reveal entanglement in a series of recent experiments.

Surface-adsorbed rare-earth nanostructures are ideal platforms to investigate the interplay between intra-atomic interactions and multiorbital spin configurations. However, addressing these properties has posed severe experimental and theoretical challenges. Here, we use the orbital selectivity offered by x-ray absorption spectroscopy to quantify the Coulomb integrals of Nd atoms on conductive surfaces directly from experimental quantities, as well as the variation of individual orbital occupation upon cluster nucleation. Using x-ray magnetic circular dichroism we identify magnetic moments of the order of 0.$1-0.2{\mu }_{\mathrm{B}}$ at the $5d$ orbitals and their magnetic coupling with the $4f$ spins. Our results validate orbital-resolved x-ray spectroscopy as a reliable method for quantifying complex multiorbital interactions in surface-adsorbed lanthanides.

The effect of hidden spin polarization (HSP) has expanded the material pool for spintronics and provided new physical insights into relevant hidden phenomena such as optical polarization, valley polarization, orbital polarization, and Berry curvature. Here, we uncover an intrinsic HSP in topological Dirac semimetals originating from the three-dimensional quantum Hall effect. This local spin polarization arises through nonequilibrium processes, where the Landau levels tilt due to the $\mathcal{P}\mathcal{T}$-symmetry breaking induced by crossed electric and magnetic fields. We find that the nonequilibrium HSP exhibits directional selectivity owing to the spin-momentum-surface locking of the Fermi arcs. As a result of the Weyl-orbit quantization, the local spin polarization exhibits quantum oscillations with sample thickness and displays plateaus as the Fermi energy varies. This nonequilibrium HSP, which can be detected through current-induced nonlocal spin-orbit torques, is unique to the Weyl orbits. Our findings present a novel mechanism for detecting Weyl orbits and for nonlocally controlling magnetization using external electric fields.