We propose a method to numerically determine the location of a critical point in general systems using the finite-size scaling of Lee-Yang zeros. This method makes use of the fact that the ratios of Lee-Yang zeros on various spatial volumes intersect at the critical point. While the method is similar to the Binder-cumulant analysis, it is advantageous in suppressing the finite-volume effects arising from the mixing of variables in general systems. We show that the method works successfully for numerically locating the critical point in the three-dimensional three-state Potts model with a nonzero external field.

In this work, we demonstrate a new method for quantum state control and nondestructive internal quantum state readout of a single ${\mathrm{HD}}^{+}$ ion in the rovibrational ground state in a Penning trap. Furthermore, we demonstrate a measurement of the magnetic trapping field with the same ion to sub-ppb uncertainty. This could enable nondestructive, high-precision spectroscopy of the hyperfine, Zeeman, and rovibrational level structure of single molecular ions. In particular, this technique can be applied to ${\mathrm{H}}_2^{+}$ as well as to its antimatter equivalent, ${\overline{\mathrm{H}}}_2^{-}$, with the potential for high-precision tests of charge-parity-time reversal symmetry beyond current sensitivities [Phys. Scr. T 1995, 423 (1995), Phys. Rev. A 98, 010101 (2018)].

Altermagnetism, a new class of collinear compensated magnetic phase, has garnered tremendous interest because of its rich physics and promising applications. Physical models and verified material candidates for altermagnetism remain limited. Here, we propose a general scheme to construct altermagnetic models, which explicitly exhibits the blend of ferromagnetic and antiferromagnetic correlations in real space via the design of spin clusters, echoing the observation that properties of altermagnets resemble a mixture of ferromagnets and antiferromagnets. We show that in some of our models, the desired altermagnetic order can be spontaneously realized by electron-electron interaction in a broad range of the phase diagram. This development facilitates the study of fascinating physics of altermagnetism and sheds light on the discovery of new altermagnetic materials.

Spontaneous formation of knots in long polymers at equilibrium is inevitable but becomes rare in sufficiently short chains. Here, we show that knotting increases by orders of magnitude in diblock polymers having a fraction $p$ of self-propelled monomers. Remarkably, this enhancement is not monotonic in $p$ with an optimal value independent of the monomer’s activity. By monitoring the knot’s size and position we elucidate the mechanisms of its formation, diffusion, and untying and ascribe the nonmonotonic behavior to the competition between the rate of knot formation and the knot’s lifetime. These findings suggest a nonequilibrium mechanism to generate entangled filaments at the nano- and microscales.

We present the first numerical simulations of asymptotically flat space-times whose computational domain includes past and future null infinity. As an application, we explore the scattering of a gravitational wave in a black hole space-time. The study is conducted in the fully nonlinear regime using an initial boundary value problem formulation of Friedrich’s generalized conformal field equations. We calculate the Bondi energy, Bondi news, and gravitational information at both past and future null infinity and discuss their relationships.

The decay $B\to \rho \ell \overline{\nu }$ is an attractive process for determining the magnitude of the smallest Cabibbo-Kobayashi-Maskawa matrix element, $|V_{ub}|$, and can provide new insights into the origin of the long-standing exclusive-inclusive discrepancy in determinations of this standard-model parameter. This requires a nonperturbative QCD calculation of the $B\to \rho$ form factors $V$, $A_0$, $A_1$, and $A_{12}$. The unstable nature of the $\rho$ resonance has prevented precise lattice QCD calculations of these form factors to date. Here, we present the first lattice QCD calculation of the $B\to \rho$ form factors in which the $\rho$ is treated properly as a resonance in $P$-wave $\pi \pi$ scattering. To this end, we use the Lellouch-Lüscher finite-volume formalism to compute the $B\to \pi \pi$ form factors as a function of both momentum transfer and $\pi \pi$ invariant mass, and then analytically continue to the $\rho$ resonance pole. This calculation is performed with $2+1$ dynamical quark flavors at a pion mass of approximately 320 MeV, and demonstrates a clear path toward results at the physical point.

In this Letter, the first evidence of the ${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{He}}$ antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number $A=4$, specifically $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$. In addition, the antiparticle-to-particle ratios for both hypernuclei (${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{H}}/{}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and ${}_{\overline{\mathrm{\Lambda }}}{}^4\overline{\mathrm{He}}/{}_{\mathrm{\Lambda }}{}^4\mathrm{He}$) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb-Pb collisions, collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The yields measured for the average of the charge-conjugated states are found to be $[0.78\pm 0.19(\mathrm{stat})\pm 0.17(\mathrm{syst})]\times {10}^{-6}$ for the $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $[1.08\pm 0.34(\mathrm{stat})\pm 0.20(\mathrm{syst})]\times {10}^{-6}$ for the $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$, and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$ excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of $3.3\sigma$ from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within $0.6\sigma$ with the present measurements. Additionally, the measured $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{H}$ and $(\mathrm{anti}){}_{\mathrm{\Lambda }}{}^4\mathrm{He}$ masses are compatible with the world-average values within the uncertainties.

The MUonE experiment aims to extract the hadronic contribution to the muon anomalous magnetic moment from a precise measurement of the muon-electron differential scattering cross section. We show that MUonE can also discover thermal relic dark matter using only its nominal experimental setup. Our search strategy is sensitive to models of dark matter in which pairs of pseudo-Dirac fermions are produced in muon-nucleus scattering in the target, and the heavier state decays semivisibly to yield dilepton pairs displaced downstream from the interaction point. This approach can probe sub-GeV thermal-relic dark matter whose cosmological abundance is governed by the same model parameters that set the MUonE signal strength. Furthermore, our results show that the downstream electron calorimeter plays a key role in rejecting backgrounds for this search, thereby providing strong motivation for the MUonE to keep this component in the final experimental design.

This Letter reports new results from the HAYSTAC experiment’s search for dark matter axions in our galactic halo. It represents the widest search to date that utilizes squeezing to realize subquantum limited noise. The new results cover $1.71\mathrm{\mu }\mathrm{eV}$ of newly scanned parameter space in the mass ranges $17.28–18.44\mathrm{\mu }\mathrm{eV}$ and $18.71–19.46\mathrm{\mu }\mathrm{eV}$. No statistically significant evidence of an axion signal was observed, excluding couplings $|g_{\gamma }|\ge 2.75\times |g_{\gamma }^{\mathrm{KSVZ}}|$ and $|g_{\gamma }|\ge 2.96\times |g_{\gamma }^{\mathrm{KSVZ}}|$ at the 90% confidence level over the respective region. By combining this data with previously published results using HAYSTAC’s squeezed state receiver, a total of $2.27\mathrm{\mu }\mathrm{eV}$ of parameter space has now been scanned between $16.96–19.46\mathrm{\mu }\mathrm{eV}$$\mu \mathrm{eV}$, excluding $|g_{\gamma }|\ge 2.86\times |g_{\gamma }^{\mathrm{KSVZ}}|$ at the 90% confidence level. These results demonstrate the squeezed state receiver’s ability to probe axion models over a significant mass range while achieving a scan rate enhancement relative to a quantum-limited experiment.

We show that spatially structured radiation generates a second harmonic even in homogeneous and isotropic media. The effect originates from the nonlocality of the electric response to the structured electromagnetic field. We develop an analytical theory of such a second harmonic generation in conducting two-dimensional systems. For the general type of structured radiation, we calculate the emerging electric currents at the double frequency and the emitted second harmonic radiation. The theory applied to twisted light reveals that the angular momentum of light doubles in the second harmonic emission. Our results pave the way for light second harmonic generation and structuring beyond the constraints imposed by crystal symmetry.

An analog of the optical polarizer-analyzer for electrons, a spin filter based on a freestanding ferromagnetic (FM) nanomembrane covering the entrance of the microchannel plate (MCP) was applied for efficient spin filtering and electron amplification in the 2D field of view. To study the spin dependent transmission, we constructed a spin-triode device (spintron), which consists of a compact proximity focused vacuum tube with the ${\mathrm{Na}}_2\mathrm{KSb}$ spin-polarized electron source, the FM-MCP and phosphor screen placed to run parallel to each other. Here, we demonstrate the fabrication of FM nanomembranes consisting of a $[\mathrm{Co}/\mathrm{Pt}]$ superlattice deposited on a freestanding 3 nm ${\mathrm{SiO}}_2$ layer with a total thickness of 10 nm. The FM-MCP has $\sim {10}^6$ channels with a single-channel Sherman function $S=0.6$ and a transmission of $\sim 1.5\times {10}^{-3}$ in the low electron energy range. The FM-MCP-based device provides a compact optical method for measuring the spin polarization of free electron beams in the imaging mode and is well suited for photoemission spectroscopy and microscopy methods.

Lattice models are valuable tools to gain insight into the statistical physics of heteropolymers. We rigorously map the partition function of these models into a vacuum expectation value of a ${\mathbb{Z}}_2$ lattice gauge theory (LGT), with both fermionic and bosonic degrees of freedom. Because the associated path integral expression is not affected by a sign problem, it is amenable to Monte Carlo (MC) sampling in both the sequence and structure space, unlike conventional polymer field theory. At the same time, since the LGT encoding relies on qubits, it provides a framework for future efforts to capitalize on the development of quantum computing hardware. We discuss two illustrative applications of our formalism: first, we use it to characterize the thermodynamically stable sequences and structures of small heteropolymers consisting of two types of residues. Next, we assess its efficiency to sample ensembles of compact structures, finding that the MC decorrelation time scales only linearly with the chain length.

Asymmetric energy exchange interactions, also known as Hatano-Nelson type couplings, enable the study of non-Hermitian physics and associated phenomena like the non-Hermitian skin effect and exceptional points (EPs). Since these interactions are by definition nonreciprocal, there have been very few options for implementations in integrated photonics. In this work, we show that asymmetric couplings are readily achievable in integrated photonic systems through time-domain dynamic modulation. We experimentally study this concept using a two-resonator photonic molecule produced in a lithium niobate on insulator platform that is electro-optically modulated by rf stimuli. We demonstrate the dynamic tuning of the Hatano-Nelson coupling between the resonators, surpassing the asymmetry that has been achieved in previous work, to reach an EP for the first time. We are additionally able to flip the relative sign of the couplings for opposite directions by going past the EP. Using this capability, we show that the through-chain transport can be configured to exhibit both giant ($\sim 60\mathrm{dB}$) optical contrast as well as photonic gyration or nonreciprocal $\pi$ phase contrast.

The laser excitation of magnetization dynamics without applying external fields is a topic of high interest for its potential applications (e.g., magnetic memories, oscillators, and THz emitters). We explore the use of an ultrashort infrared laser pulse for triggering transient changes in a magnetic vortex, probing the induced dynamics by time-resolved magnetic helicoidal dichroism (MHD) in resonant extreme ultraviolet scattering. MHD describes the optical response of a magnetic sample upon sign reversal of either the light orbital angular momentum or the magnetization and was demonstrated to be sensitive to the sample spin texture. Here, we show that, in addition to the well-known ultrafast demagnetization and remagnetization laser-induced processes, the analysis of the MHD signal, supported by micromagnetic simulations, provides direct evidence of important transient reorganizations of the spin texture. In particular, we find that an ultrafast laser pulse of sufficient intensity can induce a surface transient magnetic texture where the vortex curling direction is reversed with respect to the bulk. This result provides insight into the preparation of metastable complex spin states in magnetic films by optical methods without applying an external field, which is of relevance for novel applications in data storage and manipulation.

In nonequilibrium steady states of Markov jump processes, we derive exact fluctuation-response relations (FRRs) that express the covariance between any pair of currents in terms of static responses in a notably simple form, thus generalizing the fluctuation-dissipation theorem far from equilibrium. We begin by considering perturbations in the symmetric part of the rates. We demonstrate that FRRs imply a hierarchy of thermodynamic bounds. These hierarchies prove the recently conjectured response thermodynamic uncertainty relation, which bounds the ratio between any current’s response and its variance by the entropy production rate (EPR). We furthermore strengthen this bound in two distinct ways, using a partial EPR in one case and a pseudo-EPR in the other. For perturbations in the antisymmetric part of the rates, we show that the ratio between any current’s response and its variance is bounded by traffic, a metric representing the total number of transitions per unit time in the system. As an application, we use FRRs to explain the origin of positive correlations between currents in Coulomb-blockaded systems previously observed in experiments.

It is widely established that a lower bound on the dark matter particle mass, $m$, can be obtained by demanding that the de Broglie wavelength in a given galaxy must be smaller than the virial radius of the galaxy, leading to $m\gtrsim {10}^{-22}\mathrm{eV}$ when applied to typical dwarf galaxies. This lower limit has never been derived precisely or rigorously. We use stellar kinematical data for the Milky Way satellite galaxy Leo II to self-consistently reconstruct a statistical ensemble of dark matter wave functions and corresponding density profiles. By comparison to a data-driven, model-independent reconstruction, and using a variant of the maximum mean discrepancy as a statistical measure, we determine that a self-consistent description of dark matter in the local Universe requires $m>2.2\times {10}^{-21}\mathrm{e}\mathrm{V}$ ($\mathrm{C}\mathrm{L}>95\%$). This lower limit is free of any assumptions pertaining to cosmology, microphysics (including spin), or dynamics of dark matter, and only assumes that it is predominantly composed of a single bosonic particle species.

The energy-level degeneracies, also known as exceptional points (EPs), are crucial for comprehending emerging phenomena in materials and enabling innovative functionalities for devices. Since EPs were proposed over half a century ago, only two types of EPs have been experimentally discovered, revealing intriguing phases of materials such as Dirac and Weyl semimetals. These discoveries have showcased numerous exotic topological properties and novel applications, such as unidirectional energy transfer. Here, we report the observation of a novel type of EP, named the Dirac EP, utilizing a nitrogen-vacancy center in diamond. Two of the eigenvalues are measured to be degenerate at the Dirac EP and remain real in its vicinity. This exotic band topology associated with the Dirac EP enables the preservation of the symmetry when passing through, and makes it possible to achieve adiabatic evolution in non-Hermitian systems. We examined the degeneracy between the two eigenstates by quantum state tomography, confirming that the degenerate point is a Dirac EP rather than a Hermitian degeneracy. Our research of the distinct type of EP contributes a fresh perspective on dynamics in non-Hermitian systems and is potentially valuable for applications in quantum control in non-Hermitian systems and the study of the topological properties of EPs.

Electromagnetic (EM) multipath interference is difficult to address with passive approaches due to two physical restrictions—the shared frequency of the initial and interfering signals and their variable incident angles. Thus, to address multipath interference, the spatial impedance, i.e., the impedance structured in three-dimensional space, must be adjusted in response to the incident angles of multiple signals with the same frequency, which is impossible with classic linear time-invariant (LTI) systems. We present a design concept for metasurface-based spatial filters to overcome LTI behavior and suppress multipath interference signals using a time-varying interlocking mechanism without any active biasing systems. The proposed filters are comprised of metasurface panels and internally coupled circuit elements including MOSFETs, which permit accepting only the first incoming wave, while adjusting the spatial impedance to reject time-delayed waves from different angles. The proposed concept is numerically and experimentally validated to have a shielding effectiveness of more than 10 dB. This Letter opens a new avenue for passive yet time-varying selective EM metasystems, enabling the adjustment of spatially complicated EM waves and fields even at the same frequency.

Plasma waves in the magnetosphere scatter electrons, causing them to precipitate into Earth’s atmosphere, imparting their temporal characteristics to diffuse auroras. In a case study of conjugate radar and satellite observations, we demonstrate a close and unprecedented association between enhanced electrostatic cyclotron harmonic wave activity in the magnetosphere and the appearance of meter-scale plasma turbulence a few seconds later in the lower ionosphere on nearby magnetic field lines. Such direct structuring of the ionosphere carries implications for our understanding of space weather.

Almost every electron microscopy experiment is fundamentally limited by radiation damage. Nevertheless, little is known about the onset and progression of radiolysis in beam-sensitive materials. Here we apply ambient-temperature scanning nanobeam electron diffraction to record simultaneous dual-space movies of organic and organometallic nanocrystals at sequential stages of beam-induced radiolytic decay. We show that the underlying mosaic of coherently diffracting domains undergoes internal rearrangement as a function of accumulating electron fluence, causing the intensities of some associated Bragg reflections to fade nonmonotonically. Furthermore, we demonstrate that repeated irradiation at a single probe position leads to the isotropic propagation of delocalized radiolytic damage well beyond the direct footprint of the incident beam. We refer to these expanding tides of amorphization as “impact craters.”