The recently discovered mechanism of reverse internal conversion vibrational autodetachment (RICVAD), by which an excess electron is emitted at specific energies from an isolated hot ground state anion, is mediated by the statistical population of a dipole-bound state. Here, we consider how this process is influenced by the presence of up to two water molecules. Using anion photoelectron imaging of the nitrobenzene radical anion, ${\mathrm{NB}}^{-}$, clustered to water molecules, we find that RICVAD remains active for ${\mathrm{NB}}^{-}{({\mathrm{H}}_2\mathrm{O})}_1$. However, we also find that an additional decay channel opens at higher photoexcitation energies, which arises from dissociation of the cluster upon accessing an electronic resonance of ${\mathrm{NB}}^{-}{({\mathrm{H}}_2\mathrm{O})}_1$, forming hot isolated ${\mathrm{NB}}^{-}$, which then undergoes RICVAD. ${\mathrm{NB}}^{-}{({\mathrm{H}}_2\mathrm{O})}_2$ also shows evidence of RICVAD, but its signatures are obscured by other low energy electron signal. Our work shows that the RICVAD mechanism remains possible in a complex environment and shows how resonance dynamics are influenced by hydration.

We introduce a spectroscopic approach to primary gas thermometry, harnessing precise optical cavity resonance frequencies and ab initio molecular line intensity calculations. By utilizing CO (3-0) vibrational band lines and cavity mode dispersion spectroscopy, we achieve an uncertainty of 82 ppm (24 mK at 296 K) in line intensity ratio thermometry—over an order of magnitude lower than any previously reported spectroscopic thermometry at gas pressures above 1.2 kPa. This method extends high-precision spectroscopic thermometry across a pressure range an order of magnitude larger than prior techniques, enabling a fully optical, noncontact, and molecule-selective primary amount-of-substance measurement. We further demonstrate sub-permille uncertainty in gas concentration measurements across pressures from 50 Pa to 20 kPa, significantly enhancing the precision and versatility of spectroscopic gas metrology.

We explore the limits of atomic coherence and measurement precision in a ${}^{87}\mathrm{Sr}$ optical lattice clock. We perform a detailed characterization of key effects, including lattice Raman scattering and atomic collisions in a shallow lattice configuration, determining a 174(28) s ${}^3{P}_0$ clock state lifetime. Investigation of atomic coherence across a range of lattice depths and atomic densities reveals decoherence mechanisms related to photon scattering and atomic interaction. At a reduced density, we observe a coherence time of 118(9) s, approaching the fundamental limit set by spontaneous emission. Guided by this coherence understanding, we demonstrate a clock instability for an atomic ensemble of $1.5\times {10}^{-18}$ at 1 s in fractional frequency units. Our results are important for further advancing the state of the art of an optical lattice clock for fundamental physics applications.

Large single-atom cooperativity in quantum systems is important for quantum information processing. Here, we propose to exponentially enhance the single-atom cooperativity parameter by exploiting the strongly localized effect of modes in cavity quantum electrodynamics (QED) systems. By increasing the wing width of a cavity with special geometry symmetry, the interference property allows us to exponentially improve the quality factor $Q$ without altering the mode volume $V$ for cavities supporting subwavelength light modes. This effectively overcomes the trade-off between $Q$ and $V$ in conventional subwavelength Fabry-Pérot cavities. Consequently, we demonstrate the occurrence of ultralong vacuum Rabi oscillations and the generation of strong photon blockade by enhancing the single-atom cooperativity parameter. This Letter offers a promising approach for advancing coherent manipulation and holds significant potential for applications in establishing longer-distance quantum communication networks, enhancing the precision and stability of quantum sensors, and improving the efficiency of quantum algorithms.

The laminar-turbulent transition in straight pipes is believed to occur through a continuous nonequilibrium phase transition in the directed percolation universality class. However, in curved pipes or in the presence of body forces it is possible to observe a discontinuous transition and other phenomenology which seem inconsistent with the emerging consensus. Here, we consider the perturbing effects of body forces and incorporate them into a minimal Landau theory of the transition. We calculate the phase diagram as a function of Reynolds number and body force strength, and show that above a threshold strength of the latter, there is a tricritical point which accounts for the observed discontinuity behavior, including spatially heterogeneous states. Our results are consistent with recent experiments in centrifugal pipes and direct numerical simulations of heated flows.

Negative thermal expansion (NTE) is an unusual yet highly useful phenomenon that has been extensively studied in numerous crystals, including ceramics, alloys, and metal-organic frameworks. This Letter reports an unprecedented NTE in an amorphous ${\text{Fe}}_{87.5}{\mathrm{Y}}_3{\text{Zr}}_{1.5}{\mathrm{B}}_8$ alloy that lacks a periodic atomic arrangement. Such an NTE is significant for metallic materials and extends over a wide temperature range (${\alpha }_1=-6.9\times {10}^{-6}{\mathrm{K}}^{-1}$, 200–375 K). We demonstrate that this NTE is intrinsic to the amorphous nature of the alloy and is correlated with Fe moment. Extended x-ray absorption fine structure reveals a strong NTE for nearest neighboring Fe-Fe pairs. Further analysis using a x-ray pair distribution function indicates that the amorphous ${\mathrm{Fe}}_{87.5}{\mathrm{Y}}_3{\mathrm{Zr}}_{1.5}{\mathrm{B}}_8$ alloy, serving as a transition state, exhibits a tendency toward local ordered atomic arrangement. A complex interplay among local structure, magnetic interaction, and thermal relaxation results in volume contraction upon heating below $T_C$. This Letter introduces amorphous alloys as a new family of materials with NTE functionality, offering interesting prospects for both scientific research and practical applications.

We approach the problem of heterogeneous dynamic fracture by considering spatiotemporal perturbations to planar crack fronts. Front propagation is governed by local energy balance between the elastic energy per unit area available to fracture $G$ and the dissipation in creating new surfaces. $G$ is known analytically as a perturbation series in the crack front fluctuation. For dissipation that monotonically increases with the crack speed, we derive an equation of motion for crack fronts that is second-order accurate. In the linear order, heterogeneity does not change the net speed of fracture. In the second order, nonlinear interactions of the front and the heterogeneous landscape populate an intermediate-scale fluctuation spectrum. We find that, when dissipation weakly grows with velocity, nonlinearities globally amplify dissipation and reduce the crack speed. Strong velocity dependence, however, mitigates toughening effects and may facilitate fracture.

Electric control of spin in insulators is desired for low-consumption and ultrafast spintronics, but the underlying mechanism remains largely unexplored. Here, we propose an intrinsic effect of dynamic spin generation driven by time-varying electric field. In the intraband response regime, it can be nicely formulated as a Berry curvature effect and leads to two phenomena that are forbidden in the dc limit: linear spin generation in nonmagnetic insulators and intrinsic Néel spin-orbit torque in $\mathcal{PT}$-symmetric antiferromagnetic insulators. These phenomena are driven by the time derivative of field rather than the field itself, and have a quantum origin in the first-order dynamic anomalous spin polarizability. Combined with first-principles calculations, we predict sizable effects driven by the terahertz field in nonmagnetic monolayer Bi and in antiferromagnetic even-layer ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$, which can be detected in experiment.

We show that the nonreciprocity of hydrodynamic electron transport in noncentrosymmetric conductors with broken time-reversal symmetry is significantly enhanced compared to the disorder-dominated regime. This enhancement is caused by the linear dependence of the viscosity of the electron liquid on the flow velocity, which is allowed in the absence of time-reversal symmetry and Galilean invariance. The resulting nonlinear flows break dynamical similarity, and, thus, in addition to the Reynolds number, they are characterized by a second dimensionless parameter, the nonreciprocity number. The latter is linear in velocity but independent of system size. We determine the nonlinear conductance of a Hall bar and show that the nonreciprocal correction to the current can be of comparable magnitude to its reciprocal counterpart.

A biorthonormal-block density-matrix renormalization group algorithm is proposed to accurately compute properties of large-scale non-Hermitian many-body systems, in which a renormalized-space partition of the non-Hermitian reduced density matrix is implemented to fulfill the prerequisite for the biorthonormality of the renormalization group (RG) transformation and to optimize the construction of saved Hilbert spaces. A redundancy in saved spaces of the reduced density matrix is exploited to reduce a condition number resulting from the nonunitarity of the left and right transformation matrices, in order to ensure the numerical stability of the RG procedure. The algorithm is successfully applied to an interacting fermionic Su-Schrieffer-Heeger model with nonreciprocal hoppings and staggered complex chemical potential, exhibiting novel many-body phenomena.

Charge density wave (CDW) order is a key property of high-$T_c$ cuprates, but its boundaries in the phase diagram and potential connections to other phases remain controversial. We report nuclear magnetic resonance (NMR) measurements in the prototypical cuprate ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{\mathrm{y}}$ demonstrating that short-range static CDW order remains robust at optimal doping ($p=0.165$), exhibiting a strength and temperature dependence in the normal state similar to those observed at $p\simeq 0.11$ in the underdoped regime. For an overdoped sample with $p=0.184$, we detect no static CDW down to $T=T_c$, though weak CDW order plausibly emerges below $T_c$. More broadly, we argue that both quenched disorder and competition with superconductivity influence the apparent boundary of the CDW phase, likely causing an underestimation of its intrinsic extent in doping. These findings challenge the view that the CDW phase boundary lies below $p^{*}\simeq 0.19$, widely regarded as the critical doping where the pseudogap phase ends in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{\mathrm{y}}$.

Inspired by recent experiments, we present a phase-field model of microphase separation in an elastomer swollen with a solvent. The imbalance between the molecular scale of demixing and the mesoscopic scale beyond which elasticity operates produces effective long-range interactions, forming stable finite-sized domains. Our predictions concerning the dependence of the domain size and transition temperature on the stiffness of the elastomer are in good agreement with the experiments. Analytical phase diagrams, aided by numerical findings, capture the richness of the microphase morphologies, paving the way to create stable, patterned elastomers for various applications.

The collective chasing dynamics of nonreciprocally coupled densities leads to stable traveling waves which can be mapped to a model for emergent flocking. In this Letter, we couple the nonreciprocal Cahn-Hilliard model to a fluid to minimally describe scalar active mixtures in a suspension, with the aim to explore the stability of the waves, i.e., the emergent flock in the presence of self-generated fluid flows. We show that the emergent polarity is linearly unstable to perturbations for a specific sign of the active stress recalling instabilities of orientational order in a fluid. Using numerical simulations, we find, however, that nonreciprocity stabilizes the waves against the linear instability in a large region of the phase space.

Distributed quantum metrology (DQM) enables the estimation of global functions of $d$ distributed parameters beyond the capability of separable sensors. Continuous-variable DQM involves using a linear network with at least one nonclassical input. Here, we fully elucidate the structure of linear networks with two nonvacuum inputs, which allows us to prove a number of fundamental properties of continuous-variable DQM. While measuring the sum of $d$ parameters at the Heisenberg limit can be achieved with a single nonvacuum input, we show that two inputs, one of which can be classical, are required to measure an arbitrary linear combination of $d$ parameters and an arbitrary global function of the parameters. We obtain a universal and tight upper bound on the sensitivity of DQM networks with two inputs, and completely characterize the properties of the nonclassical input required to obtain a quantum advantage. This reveals that a wide range of nonclassical states makes this possible, including a squeezed vacuum. We also show that, for a class of nonclassical inputs, local photon number detection will achieve the maximum sensitivity. Finally we show that a general DQM network has two distinct regimes. The first achieves Heisenberg scaling. In the second the nonclassical input is much weaker than the coherent input, nevertheless providing a multiplicative enhancement to the otherwise classical sensitivity.

Fluctuations in ultralight dark matter produce significant metric perturbations, which may be detected by monitoring the arrival times of light from millisecond pulsars. While searches using this technique are already underway, they do not consistently account for the statistical properties of the dark matter field. The statistics of this field depend on the velocity dispersion of dark matter and, consequently, its coherence length. In the mass range relevant for pulsar timing arrays, the coherence length is comparable to separations between pulsars, making it crucial to incorporate its effects into the analysis. This Letter presents a consistent statistical method for gravitational direct detection of ultralight dark matter. Our key result is the derivation of the two-point function of the metric fluctuations, which we apply to pulsar timing and discuss its implementation in future searches.

We show that primordial adiabatic curvature fluctuations generate an instability of the scalar field sourcing a kination era. We demonstrate that the generated higher Fourier modes constitute a radiationlike component dominating over the kination background after about 11 e-folds of cosmic expansion. Current constraints on the extra number of neutrino flavors $\mathrm{\Delta }{N}_{\mathrm{eff}}$ thus imply the observational bound of approximately 10 e-folds, representing the most stringent bound to date on the stiffness of the equation of state of the pre–Big Bang–nucleosynthesis universe.

We study quantum M2-branes in holographic backgrounds and show that their moduli spaces of zero modes are localized according to an R-symmetry Killing vector. We discuss the relation with recent results in the context of equivariant localization in gauged supergravity and argue its origin within M-theory path integrals expanded in saddle points over M2-branes. We argue that the M2-brane partition function, including its nonperturbative corrections, should be compared to the field theory grand canonical partition function. Our results extend recent observations in the context of the giant graviton expansion of superconformal indices to generic supersymmetric anti–de Sitter boundary conditions. As a byproduct we predict nonperturbative corrections to a variety of supersymmetric observables of the Aharony-Bergman-Jafferis-Maldacena theory.

In high-energy collisions far above the electroweak scale, the effects of electroweak symmetry breaking are expected to become parametrically small $\delta \sim M_W/E$. This defines the extent to which the electroweak gauge symmetry is restored: (i) the physics of the transverse gauge bosons and fermions is described by a massless theory in the unbroken phase; (ii) the longitudinal gauge bosons behave like the Goldstone bosons and join the Higgs boson to restore the unbroken O(4) symmetry in the original Higgs sector. Using the unique feature of the radiation amplitude zeros in gauge theory, we propose to study the electroweak symmetry restoration quantitatively by examining the processes for the gauge boson pair production $W^{\pm }\gamma ,W^{\pm }Z$, and $W^{\pm }H$ at the LHC and muon colliders.