We investigate the wrinkling dynamics of an elastic filament immersed in a viscous fluid submitted to compression at a finite rate with experiments and by combining geometric nonlinearities, elasticity, and slender body theory. The drag induces a dynamic lateral reinforcement of the filament leading to growth of wrinkles that coarsen over time. We discover a new dynamical regime characterized by a time scale with a nontrivial dependence on the loading rate, where the growth of the instability is superexponential and the wave number is an increasing function of the loading rate. We find that this time scale can be interpreted as the characteristic time over which the filament transitions from the extensible to the inextensible regime. In contrast with our analysis with moving boundary conditions, Biot’s analysis in the limit of infinitely fast loading leads to rate independent exponential growth and wavelength.

We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of $F_C=0.2\mathrm{mJ}{\mathrm{cm}}^{-2}$, the band gap narrows transiently, while it is enhanced above $F_C$. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ with light on the femtosecond time scale.

Photoionization of molecular species is, essentially, a multipath interferometer with both experimentally controllable and intrinsic molecular characteristics. In this work, XUV photoionization of impulsively aligned molecular targets (${\mathrm{N}}_2$) is used to provide a time-domain route to “complete” photoionization experiments, in which the rotational wave packet controls the geometric part of the photoionization interferometer. The data obtained is sufficient to determine the magnitudes and phases of the ionization matrix elements for all observed channels, and to reconstruct molecular frame interferograms from lab frame measurements. In principle, this methodology provides a time-domain route to complete photoionization experiments and the molecular frame, which is generally applicable to any molecule (no prerequisites), for all energies and ionization channels.

We report the observation of coherent surface states on cubic perovskite oxide ${\mathrm{SrVO}}_3(001)$ thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a $d_{xy}$-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost ${\mathrm{VO}}_2$ plane play a critical role in controlling the coherent surface state via modulating orbital state.

We report muon-spin rotation and neutron-scattering experiments on nonmagnetic Zn impurity effects on the static spin-stripe order and superconductivity of the La214 cuprates. Remarkably, it was found that, for samples with hole doping $x\approx 1/8$, the spin-stripe ordering temperature $T_{\mathrm{so}}$ decreases linearly with Zn doping $y$ and disappears at $y\approx 4\%$, demonstrating a high sensitivity of static spin-stripe order to impurities within a ${\mathrm{CuO}}_2$ plane. Moreover, $T_{\mathrm{so}}$ is suppressed by Zn in the same manner as the superconducting transition temperature $T_c$ for samples near optimal hole doping. This surprisingly similar sensitivity suggests that the spin-stripe order is dependent on intertwining with superconducting correlations.

We present the results of a combined ${}^7\mathrm{Li}$-NMR and diffraction study on ${\mathrm{LiGa}}_{0.95}{\mathrm{In}}_{0.05}{\mathrm{Cr}}_4{\mathrm{O}}_8$, a member of the ${\mathrm{LiGa}}_{1-x}{\mathrm{In}}_x{\mathrm{Cr}}_4{\mathrm{O}}_8$ “breathing” pyrochlore family. Via specific heat and NMR measurements, we find that the complex sequence of first-order transitions observed for ${\mathrm{LiGaCr}}_4{\mathrm{O}}_8$ is replaced by a single second-order transition at $T_f=11\mathrm{K}$. Neutron and x-ray diffraction rule out both structural symmetry lowering and magnetic long-range order as the origin of this transition. Instead, reverse Monte Carlo fitting of the magnetic diffuse scattering indicates that the low-temperature phase may be described as a collinear spin nematic state, characterized by a quadrupolar order parameter. This state also shows signs of short-range order between collinear spin arrangements on tetrahedra, revealed by mapping the reverse Monte Carlo spin configurations onto a three-state color model.

We establish the existence of bulk odd-frequency superconductivity in ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ and show that an intrinsic Kerr effect is direct evidence of this state. We use both general two- and three-orbital models, as well as a realistic tight-binding description of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ to demonstrate that odd-frequency pairing arises due to finite hybridization between different orbitals in the normal state, and is further enhanced by finite interorbital pairing.

We introduce a new optimization procedure for Euclidean path integrals, which compute wave functionals in conformal field theories (CFTs). We optimize the background metric in the space on which the path integration is performed. Equivalently, this is interpreted as a position-dependent UV cutoff. For two-dimensional CFT vacua, we find the optimized metric is given by that of a hyperbolic space, and we interpret this as a continuous limit of the conjectured relation between tensor networks and Anti–de Sitter (AdS)/conformal field theory (CFT) correspondence. We confirm our procedure for excited states, the thermofield double state, the Sachdev-Ye-Kitaev model, and discuss its extension to higher-dimensional CFTs. We also show that when applied to reduced density matrices, it reproduces entanglement wedges and holographic entanglement entropy. We suggest that our optimization prescription is analogous to the estimation of computational complexity.

We perform the first next-to-leading order computation of the ${\gamma }^{(*)}\to V$ ($\rho ,\varphi ,\omega$) exclusive impact factor in the QCD shock-wave approach and in the most general kinematics. This paves the way to the very first quantitative study of high-energy nucleon and nucleus saturation beyond the leading order for a whole range of small-$x$ exclusive processes, to be measured in $ep$, $eA$, $pp$, and $pA$ collisions at existing and future colliders.

Two-leg bosonic ladders with flux harbor a remarkable vortex-hole duality between the weak-coupling vortex lattice superfluids and strong-coupling charge-density-wave crystals. The strong-coupling crystalline states, which are realized in the vicinity of $\pi$ flux, are independent of particle statistics, and are related to the incompressible fractional quantum Hall states in the thin-cylinder limit. These fully gapped ground states, away from $\pi$ flux, develop nonzero chiral (spin) currents. Contact-interacting quantum gases permit exploration of this vortex-hole duality in experiments.

We examine the momentum, spin, and orbital angular momentum of structured monochromatic optical fields in dispersive inhomogeneous isotropic media. There are two bifurcations in this general problem: the Abraham-Minkowski dilemma and the kinetic (Poynting-like) versus canonical (spin-orbital) pictures. We show that the kinetic Abraham momentum describes the energy flux and group velocity of the wave in the medium. At the same time, we introduce novel canonical Minkowski-type momentum, spin, and orbital angular momentum densities of the field. These quantities exhibit fairly natural forms, analogous to the Brillouin energy density, as well as multiple advantages as compared with previously considered formalisms. As an example, we apply this general theory to inhomogeneous surface plasmon-polariton (SPP) waves at a metal-vacuum interface and show that SPPs carry a “supermomentum,” proportional to the wave vector $k_p>\omega /c$, and a transverse spin, which can change its sign depending on the frequency $\omega$.

Nonlinear optical interactions of light with materials originate in the microscopic response of the molecular constituents to excitation by an optical field, and are expressed by the first ($\beta$) and second ($\gamma$) hyperpolarizabilities. Upper bounds to these quantities were derived seventeen years ago using approximate, truncated state models that violated completeness and unitarity, and far exceed those achieved by potential optimization of analytical systems. This Letter determines the fundamental limits of the first and second hyperpolarizability tensors using Monte Carlo sampling of energy spectra and transition moments constrained by the diagonal Thomas-Reiche-Kuhn (TRK) sum rules and filtered by the off-diagonal TRK sum rules. The upper bounds of $\beta$ and $\gamma$ are determined from these quantities by applying error-refined extrapolation to perfect compliance with the sum rules. The method yields the largest diagonal component of the hyperpolarizabilities for an arbitrary number of interacting electrons in any number of dimensions. The new method provides design insight to the synthetic chemist and nanophysicist for approaching the limits. This analysis also reveals that the special cases which lead to divergent nonlinearities in the many-state catastrophe are not physically realizable.

We derive the phonon dynamics of magnetic metals in the presence of strong spin-orbit coupling. We show that both a dissipationless viscosity and a dissipative viscosity arise in the dynamics. While the dissipationless viscosity splits the dispersion of left-handed and right-handed circularly polarized phonons, the dissipative viscosity damps them differently, inducing circular phonon dichroism. The effect offers a new degree of manipulation of phonons, i.e., the control of the phonon polarization. We investigate the effect in Weyl semimetals. We find that there exists strong circular phonon dichroism in Weyl semimetals breaking both the time-reversal and the inversion symmetry, making them potential materials for realizing the acoustic circular polarizer.

X-ray reflectivity measurements of femtosecond laser-induced transient gratings (TG) are applied to demonstrate the spatiotemporal coherent control of thermally induced surface deformations on ultrafast time scales. Using grazing incidence x-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-Å resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in x-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period $\mathrm{\Lambda }$ can be canceled by a second, time-delayed TG excitation shifted by $\mathrm{\Lambda }/2$. The ultimate speed limits of such an ultrafast x-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments.

We use ab initio calculations to predict the thermal conductivity of cubic SiC with different types of defects. An excellent quantitative agreement with previous experimental measurements is found. The results unveil that ${\mathrm{B}}_{\mathrm{C}}$ substitution has a much stronger effect than any of the other defect types in $3C\text{−}\mathrm{SiC}$, including vacancies. This finding contradicts the prediction of the classical mass-difference model of impurity scattering, according to which the effects of ${\mathrm{B}}_{\mathrm{C}}$ and ${\mathrm{N}}_{\mathrm{C}}$ would be similar and much smaller than that of the C vacancy. The strikingly different behavior of the ${\mathrm{B}}_{\mathrm{C}}$ defect arises from a unique pattern of resonant phonon scattering caused by the broken structural symmetry around the B impurity.

The hallmark of Weyl semimetals is the existence of open constant-energy contours on their surface—the so-called Fermi arcs—connecting Weyl points. Here, we show that, for time-reversal symmetric realizations of Weyl semimetals, these Fermi arcs, in many cases, coexist with closed Fermi pockets originating from surface Dirac cones pinned to time-reversal invariant momenta. The existence of Fermi pockets is required for certain Fermi-arc connectivities due to additional restrictions imposed by the six ${\mathbb{Z}}_2$ topological invariants characterizing a generic time-reversal invariant Weyl semimetal. We show that a change of the Fermi-arc connectivity generally leads to a different topology of the surface Fermi surface and identify the half-Heusler compound LaPtBi under in-plane compressive strain as a material that realizes this surface Lifshitz transition. We also discuss universal features of this coexistence in quasiparticle interference spectra.

We report the polarization rotation of terahertz light resonant with the magnetoelectric (ME) spin excitation in the multiferroic ${(\mathrm{Fe},\mathrm{Zn})}_2{\mathrm{Mo}}_3{\mathrm{O}}_8$. This resonance reflects the frequency dispersion of the diagonal ME susceptibility (axion term), with which we quantitatively reproduce the thermal and magnetic-field evolution of the observed polarization rotation spectra. The application of the sum rule on the extrapolated dc value of the spectral weight of the ME oscillator provides insight into the dc linear ME effect. The present finding highlights a novel optical functionality of spin excitations in multiferroics that originates from diagonal ME coupling.