We report on the observation of an excited $2s$ state of a trion in a 4.2 nm wide doped $\mathrm{GaAs}/{\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ quantum well using magneto-optical Kerr effect (MOKE) spectroscopy under out-of-plane magnetic fields up to 6 T. This resonance appears slightly below the $2s$ exciton in energy. Strikingly, the $2s$ trion is found to be bound only for magnetic fields larger than 1 T. The signature of the $2s$ trion is absent in the magnetoreflectance spectra, while it is detectable in the MOKE spectra signifying the importance of the powerful technique. Similar to the $1s$ states, the $2s$ trion shows an opposite degree of magnetic-field-induced polarization compared to its exciton counterpart, in agreement with our theoretical calculations. This transfer of oscillator strength between the complexes establishes an optical fingerprint of the $2s$ excited trion.

Resetting has been shown to reduce the completion time for a stochastic process, such as the first passage time for a diffusive searcher to find a target. The time between two consecutive resetting events is drawn from a waiting time distribution $\psi (t)$, which defines the resetting protocol. Previously, it has been shown that deterministic resetting process with a constant time period, referred to as sharp restart, can minimize the mean first passage time to a fixed target. Here, we consider the more realistic problem of a target positioned at a random distance $R$ from the resetting site, selected from a given target distribution $P_T(R)$. We introduce the notion of a conjugate target distribution to a given waiting time distribution. The conjugate target distribution, $P_T^{*}(R)$, is that $P_T(R)$ for which $\psi (t)$ extremizes the mean time to locate the target. In the case of diffusion we derive an explicit expression for $P_T^{*}(R)$ conjugate to a given $\psi (t)$ that holds in arbitrary spatial dimension. Our results show that stochastic resetting prevails over sharp restart for target distributions with exponential or heavier tails.

We investigate the production of axionlike particles (ALPs) in stellar cores, where they interact with electromagnetic fields and electrons, with typical masses between $\mathcal{O}(0.1)$ and $\mathcal{O}(10)\mathrm{keV}$. These low-energy ALPs are gravitationally trapped in the orbits of stars and subsequently decay into two photons that we detect as monochromatic x-ray lines. We propose to search for these gravitationally trapped ALPs in the Alpha Centauri binary system, our closest stellar neighbor, using sensitive x-ray detectors like Chandra and eROSITA. Our search for ALP decay signals in the energy range of 0.2 keV to 10 keV yielded null results, thus establishing the most stringent limits on ALP interactions to date. In the case of ALP-electron coupling $g_{aee}\le {10}^{-15}$, we have improved the limits on the ALP-photon coupling $g_{a\gamma \gamma }$ in ALP mass range between 0.25 keV and 5 keV, compared to previous measurements, including those from GW170817, SN 2023ixf, and other sources, and specially the improvement reaches about 2 orders of magnitude at the mass of 2 keV. Even tighter constraints are set for larger $g_{aee}$.

Understanding the physical significance and spectral stability of black hole quasinormal modes is fundamental to high-precision spectroscopy with future gravitational wave detectors. Inspired by Mashhoon’s idea of relating quasinormal modes of black holes with their equivalent bound states in an inverted potential, we investigate, for the first time, energy levels and eigenfunctions of the Schwarzschild black hole quantitatively. While quasinormal modes describe the characteristic damped oscillations of a black hole, the bound states of the inverted potential are qualitatively more similar to those of the hydrogen atom. Although the physical interpretation of these states may initially be of more academic interest, it furthers our understanding of open problems related to quasinormal modes in a similar spirit to Maggiore’s interpretation of the Schwarzschild quasinormal mode spectrum. One surprising insight from the explicit calculation of bound states is that eigenfunctions corresponding to quasinormal mode overtones become rapidly delocalized and extremely loosely bound. This observation raises immediate questions about the common interpretation of quasinormal modes as excitations of the light ring region. Closely related, as a second application, we also explore the spectral stability of bound states and demonstrate that they can provide complementary insights into the quasinormal mode spectrum.

This Letter introduces a method for determining the energy spectrum of lattice quantum chromodynamics by applying the Lanczos algorithm to the transfer matrix and using a bootstrap generalization of the Cullum-Willoughby method to filter out spurious eigenvalues. Proof-of-principle analyses of the simple harmonic oscillator and the lattice quantum chromodynamics proton mass demonstrate that this method provides faster ground-state convergence than the “effective mass,” which is related to the power-iteration algorithm. Lanczos provides more accurate energy estimates than multistate fits to correlation functions with small imaginary times while achieving comparable statistical precision. Two-sided error bounds are computed for Lanczos results and guarantee that excited-state effects cannot shift Lanczos results far outside their statistical uncertainties.

Using $\psi (3686)\to {\pi }^0{h}_c$ decays from a data sample of $(27.12\pm 0.14)\times {10}^8\psi (3686)$ events collected by the BESIII detector at the BEPCII collider, $h_c$ radiative decays to multiple light hadrons below $2.8\mathrm{GeV}/c^2$—$\gamma {\pi }^{+}{\pi }^{-}$, $\gamma {\pi }^{+}{\pi }^{-}\eta$, $\gamma 2({\pi }^{+}{\pi }^{-})$, and $\gamma p\overline{p}$—are observed for the first time, each with a significance greater than $5\sigma$. The corresponding branching fractions are measured. Furthermore, intermediate states are investigated, leading to the first observation of the decay process of $h_c\to \gamma f_2(1270)\to \gamma {\pi }^{+}{\pi }^{-}$ with a significance of $5.1\sigma$. This observation represents the first instance of $h_c$ radiative decay to a tensor state.

${}^{76}\mathrm{Ge}$ can $\beta \beta$ decay into three possible excited states of ${}^{76}\mathrm{Se}$, with the emission of two or, if the neutrino is Majorana, zero neutrinos. None of these six transitions have yet been observed. The Majorana Demonstrator was designed to study $\beta \beta$ decay of ${}^{76}\mathrm{Ge}$ using a low background array of high purity germanium detectors. With 98.2 kg-y of isotopic exposure, the demonstrator sets the strongest half-life limits to date for all six transition modes. For $2\nu \beta \beta$ to the $0_1^{+}$ state of ${}^{76}\mathrm{Se}$, this search has begun to probe for the first time half-life values predicted using modern many-body nuclear theory techniques, setting a limit of $T_{1/2}>1.5\times {10}^{24}\mathrm{y}$ (90% CL).

The energy spectrum and corresponding wave functions of two bosonic particles confined in a spherically symmetric shell trap and interacting via a three-dimensional zero-range potential are computed. Confinement-induced resonances, originating entirely from the strong coupling of the relative and center-of-mass motions of the two particles, are identified as avoided crossings for certain values of the shell radius. By working close to the found resonances, these results offer a new way to control the atom-atom interaction in an atomic gas by tuning only the geometrical parameters of the shell.

Coupled optical cavities, which support normal modes, play a critical role in optical filtering, sensing, slow-light generation, and quantum state manipulation. Recent theoretical work has proposed incorporating nonlinear materials into these systems to enable novel quantum technologies. Here, we report the first experimental demonstration of squeezing generated in a quantum-enhanced coupled-cavity system, achieving a quantum noise reduction of 3.3 dB around the normal-mode splitting frequency of 7.47 MHz. We provide a comprehensive analysis of the system’s loss mechanisms and performance limitations, validating theoretical predictions. Our results underscore the promise of coupled-cavity squeezers for advanced quantum applications, including gravitational wave detection and precision sensing.

Densely arranged optical vortices are natural solutions of high-symmetry Bloch modes in photonic crystals. However, strict symmetry constraints limit the potential spatial configurations of nearfield vortices, restricting the control over light-matter interaction. Here, we demonstrate a nearfield vortex dynamic within a supercell photonic crystal. By introducing paired rotations of triangular structures, we achieve high-quality-factor Bloch mode transition from evanescent valley modes, to quasibound states in the continuum, frustrated modes, and quasivalleys. Each stage exhibits distinct nearfield vortex distributions, nonlinear overlap properties, and quality factors, revealing diverse physical behaviors for tailoring light-matter interaction. Notably, the asymmetric vortex configuration of frustrated modes enhances second harmonic generation, driven by an optimized nonlinear overlap factor. Our paired-rotation strategy offers a versatile design framework for creating supercell photonic crystals with unique nearfield vortex properties, presenting promising applications in lasing, nonlinear optics and optical forces.

Higher-order exceptional points (EPs) in optical structures enable ultrasensitive responses to perturbations. However, previous investigations on higher-order EPs have predominantly focused on coupled systems, leaving their fundamental physics in open scattering systems largely unexplored. Here, we harness wave interference to realize higher-order EPs in non-Hermitian zero-index materials connected to multiple open channels. Specifically, we show that a three-channel model can give rise to three interesting types of third-order EPs: lasing EP, reflecting EP, and absorbing EP. Notably, near the third-order absorbing EP, we show ultrasensitivity—a drastic change in output power in response to perturbations at the operating frequency—in a purely lossy system. These findings pave the way for achieving higher-order and even arbitrary-order EPs in open scattering systems, offering significant potential for advanced sensing applications.

Because of the speed of light compared to material motion, the dragging of light is difficult to observe under laboratory conditions. Here, we report on the first observation of image rotation, i.e., a dragging by the medium of the wave’s transverse structure, of Alfvén waves in plasmas. Exploiting the naturally slow group velocity of these waves, significant wave rotation is achieved for modest angular frequency. Control over the rotation of the wave’s structure is demonstrated through the plasma rotation imposed by biased electrodes. Remarkably, experimental results are well reproduced by light dragging theory derived for isotropic media, even if magnetized plasmas are anisotropic. In addition to offering new insights into the fundamental issue of angular momentum coupling between waves and media, these findings also open possibilities for new remote rotation sensing tools.

We study the zero-temperature phase diagram of two-dimensional helium-4 using neural quantum states. Our variational description allows us to address liquid and solid phases using the same functional form as well as exploring possible melting scenarios—for instance, via an intermediate hexatic phase. Notably, this is achieved by performing fixed pressure variational Monte Carlo calculations. Within the isobaric ensemble framework, we are able to clearly identify the first-order liquid-solid phase transition. We additionally compute the Rényi-2 entanglement entropy across the liquid-solid phase transition and find a sharp decrease upon freezing. Calculations for larger systems follow the metastable liquid and solid branches in the transient region, while signatures of a hexatic order coexisting with a small condensate fraction are observed only for smaller systems as a finite-size effect.

Understanding metal-water interfaces is instrumental in developing electrochemical cells for energy conversion. In this Letter, we quantify the relative contribution of the metal surface and the solvent molecules to the electronic component of the interfacial dipole moment enabled by an implementation of partially occupied Wannier functions that allows us to treat interfacial water in contact with metallic surfaces. Our calculations show that the contribution of the solvent is of overriding importance and that it mostly originates from specific deformation of the water lone pairs very close to the metal surface.

As a simplified description of the nonequilibrium dynamics of buckled dimers on the Si(001) surface, we consider the anisotropic two-dimensional (2D) Ising model and study the freezing of spatial correlations during a cooling quench across the critical point. Depending on the cooling rate, we observe a crossover from one-dimensional (1D) to 2D behavior. For rapid cooling, we find effectively 1D behavior in the strongly coupled direction, for which we provide an exact analytic solution of the nonequilibrium dynamics. For slower cooling rates, we start to see 2D behavior where our numerical simulations show an approach to the usual Kibble–Zurek scaling in 2D.

With the booming development of two-dimensional (2D) flexible devices, flexure has attracted much attention as an emerging means to modulate device performances. Here, the magnetic-optical-electrical multifield coupling mechanism of spin photocurrent in bent CrSBr monolayer is investigated through first-principles calculations. The studies show that simple mechanical bending of monolayer CrSBr can successfully achieve the spatial separation of electrons and holes. The nonequilibrium process of photogenerated carriers in bent CrSBr modulates both the shift current density and the ballistic current density, thereby enabling the photovoltaic effect. Meanwhile, the built-in electric field generated by flexure drives the device toward more efficient self-powered behavior. Moreover, this self-powered polarization devices have excellent spin photovoltaic properties and high polarization sensitivity. The present Letter creates novel opportunities for 2D spintronics and opens new avenues for realizing self-powered polarization devices.

Interacting particles diffusing in single file is a fundamental model of transport in narrow channels where particles cannot bypass each other. An important result has been obtained by Kollmann [Phys. Rev. Lett. 90, 180602 (2003)] for the mean square displacement of a tracer for any single-file model. It applies to any diffusive system, in particular the notable classes of colloidal systems and diffusive stochastic lattice gases. Since then, no analog result has been obtained in the important case where the particles are driven by an external field. Here, we fill this gap and determine the fluctuations and the skewness of the tracer’s position for any driven diffusive system. In addition, we also consider a variety of important observables such as the integrated current, the response of the system to the perturbation induced by the displacement of the tracer, and the correlations between several tracers. Furthermore, we also unveil fundamental relations underlying the out-of-equilibrium dynamics of driven diffusive systems. This work constitutes a step toward the determination of the full distribution of all these observables in driven one-dimensional systems of interacting particles.

The energy landscape of thin shells under quasistatic loading represents their potential energy as a function of their shape. It has recently been shown for a narrow plate [S. Lachmann and S. M. Rubinstein, Phil. Trans. R. Soc. A 381, 2244 (2023)] that lateral probing can induce controlled trajectories in configuration space, providing an experimental method for measuring the energy landscape of a specific structure. In this Letter, we extend this method to explore the prebuckling behavior of poked cylindrical shells through the lens of the energy landscape. This approach offers an intuitive way to combine and synthesize the deformation responses from different probing locations into a cohesive description of the prebuckling dynamics, revealing the presence of local soft spots—regions where the structure is particularly susceptible to deformation. As the system is loaded, these soft spots appear as local minima in the energy barrier to buckling and are experimentally shown to act as attractors of nearby deformation. The energy landscape framework provides a general framework for understanding prebuckling dynamics, highlighting the role of spatially extended deformations and offering a new way of safely estimating shock sensitivity to buckling in real shells.

Disorder hyperuniform (DHU) systems possess a hidden long-range order manifested as the complete suppression of normalized large-scale density fluctuations like crystals, which endows them with many unique properties. Here, we demonstrate a new organization mechanism for achieving stable DHU structures in active-particle systems via investigating the self-assembly of robotic spinners with threefold symmetric magnetic binding sites up to a heretofore experimentally unattained system size, i.e., with $\sim 1,000$ robots. The spinners can self-organize into a wide spectrum of actively rotating three-coordinated network structures, among which a set of stable DHU networks robustly emerge. These DHU networks are topological transformations of a honeycomb network by continuously introducing the Stone-Wales defects, which are resulted from the competition between tunable magnetic binding and local twist due to active rotation of the robots. Our results reveal novel mechanisms for emergent DHU states in active systems and achieving novel DHU materials with desirable properties.