A one-atom-layer compound made of one monolayer of Tl and one-third monolayer of Pb on a Si(111) surface having $\sqrt{3}\times \sqrt{3}$ periodicity was found to exhibit a giant Rashba-type spin splitting of metallic surface-state bands together with two-dimensional superconducting transport properties. Temperature-dependent angle-resolved photoelectron spectroscopy revealed an enhanced electron-phonon coupling for one of the spin-split bands. In situ micro-four-point-probe conductivity measurements with and without magnetic field demonstrated that the (Tl, Pb)/Si(111) system transformed into the superconducting state at 2.25 K, followed by the Berezinskii-Kosterlitz-Thouless mechanism. The 2D Tl-Pb compound on Si(111) is believed to be the prototypical object for prospective studies of intriguing properties of the superconducting 2D system with lifted spin degeneracy, bearing in mind that its composition, atomic and electron band structures, and spin texture are already well established.

Recent experiments on the ${\mathrm{Ba}}_{3}X{\mathrm{Sb}}_2{\mathrm{O}}_9$ family have revealed materials that potentially realize spin- and spin-orbital liquid physics. However, the lattice structure of these materials is complicated due to the presence of charged $X^{2+}\text{−}{\mathrm{Sb}}^{5+}$ dumbbells, with two possible orientations. To model the lattice structure, we consider a frustrated model of charged dumbbells on the triangular lattice, with long-range Coulomb interactions. We study this model using Monte Carlo simulation, and find a freezing temperature, $T_{\mathsf{\text{frz}}}$, at which the simulated structure factor matches well to low-temperature x-ray diffraction data for ${\mathrm{Ba}}_3{\mathrm{CuSb}}_2{\mathrm{O}}_9$. At $T=T_{\mathsf{\text{frz}}}$ we find a complicated “branching” structure of superexchange-linked $X^{2+}$ clusters, which form a fractal pattern with fractal dimension $d_f=1.90$. We show that this gives a natural explanation for the presence of orphan spins. Finally we provide a plausible mechanism by which such dumbbell disorder can promote a spin-orbital resonant state with delocalized orphan spins.

We report the first observation, in a supersonic flow, of the evolution of the Kelvin-Helmholtz instability from a single-mode initial condition. To obtain these data, we used a novel experimental system to produce a steady shock wave of unprecedented duration in a laser-driven experiment. The shocked, flowing material creates a shear layer between two plasmas at high energy density. We measured the resulting interface structure using radiography. Hydrodynamic simulations reproduce the large-scale structures very well and the medium-scale structures fairly well, and imply that we observed the expected reduction in growth rate for supersonic shear flow.

We synthesize two $\mathrm{Nb}/\mathrm{C}$ composites with an order of magnitude difference in the density of single niobium atoms substituted into defective graphitic layers. The concentration and sites of single Nb atoms are identified using aberration-corrected scanning transmission electron microscopy and density functional theory. Comparing the experimental complex permittivity spectra reveals that a representative dielectric resonance at $\sim 16\mathrm{GHz}$ originates from the intrinsic polarization of single Nb atom sites, which is confirmed by theoretical simulations. The single-atom dielectric resonance represents the physical limit of the electromagnetic response of condensed matter, and thus might open up a new avenue for designing electromagnetic wave absorption materials. Single-atom resonance also has important implications in understanding the correlation between the macroscopic dielectric behaviors and the atomic-scale structural origin.

We obtain, using semianalytical transfer operator techniques, the Edwards thermodynamics of a one-dimensional model of blocks connected by harmonic springs and subjected to dry friction. The theory is able to reproduce the linear divergence of the correlation length as a function of energy density observed in direct numerical simulations of the model under tapping dynamics. We further characterize analytically this divergence using a Gaussian approximation for the distribution of mechanically stable configurations, and show that it is related to the existence of a peculiar infinite temperature critical point.

It is known that the Yangian of $PSU(2,2|4)$ is a symmetry of the tree-level $S$ matrix of $\mathcal{N}=4$ super Yang-Mills theory. On the other hand, the complete one-loop dilatation operator in the same theory commutes with the level-one Yangian generators only up to certain boundary terms found by Dolan, Nappi, and Witten. Using a result by Zwiebel, we show how the Yangian symmetry of the tree-level $S$ matrix of $\mathcal{N}=4$ super Yang-Mills theory implies precisely the Yangian invariance, up to boundary terms, of the one-loop dilatation operator.

We perform a systematic study to explore the accuracy with which the parameters of intermediate-mass black-hole binary systems can be measured from their gravitational wave (GW) signatures using second-generation GW detectors. We make use of the most recent reduced-order models containing inspiral, merger, and ringdown signals of aligned-spin effective-one-body waveforms to significantly speed up the calculations. We explore the phenomenology of the measurement accuracies for binaries with total masses between $50M_{\odot }$ and $500M_{\odot }$ and mass ratios between 0.1 and 1. We find that (i) at total masses below $\sim 200M_{\odot }$, where the signal-to-noise ratio is dominated by the inspiral portion of the signal, the chirp mass parameter can be accurately measured; (ii) at higher masses, the information content is dominated by the ringdown, and total mass is measured more accurately; (iii) the mass of the lower-mass companion is poorly estimated, especially at high total mass and more extreme mass ratios; and (iv) spin cannot be accurately measured for our injection set with nonspinning components. Most importantly, we find that for binaries with nonspinning components at all values of the mass ratio in the considered range and at a network signal-to-noise ratio of 15, analyzed with spin-aligned templates, the presence of an intermediate-mass black hole with mass $>100M_{\odot }$ can be confirmed with 95% confidence in any binary that includes a component with a mass of $130M_{\odot }$ or greater.

Recent studies of low redshift type Ia supernovae (SN Ia) indicate that half explode from less than Chandrasekhar mass white dwarfs, implying ignition must proceed from something besides the canonical criticality of Chandrasekhar mass SN Ia progenitors. We show that 1–100 PeV mass asymmetric dark matter, with imminently detectable nucleon scattering interactions, can accumulate to the point of self-gravitation in a white dwarf and collapse, shedding gravitational potential energy by scattering off nuclei, thereby heating the white dwarf and igniting the flame front that precedes SN Ia. We combine data on SN Ia masses with data on the ages of SN Ia–adjacent stars. This combination reveals a $2.8\sigma$ inverse correlation between SN Ia masses and ignition ages, which could result from increased capture of dark matter in 1.4 vs 1.1 solar mass white dwarfs. Future studies of SN Ia in galactic centers will provide additional tests of dark-matter-induced type Ia ignition. Remarkably, both bosonic and fermionic SN Ia–igniting dark matter also resolve the missing pulsar problem by forming black holes in $\gtrsim 10\mathrm{Myr}$ old pulsars at the center of the Milky Way.

Using a sample of $771.6\times {10}^6$ $\mathrm{\Upsilon }\mathrm{\Upsilon }(4S)$ decays collected by the Belle experiment at the KEKB $e^{+}{e}^{-}$ collider, we observe, for the first time, the transition $\mathrm{\Upsilon }(4S)\to \eta h_b(1P)$ with the branching fraction $\mathcal{B}[\mathrm{\Upsilon }(4S)\to \eta h_b(1P)]=(2.18\pm 0.11\pm 0.18)\times {10}^{-3}$ and we measure the $h_b(1P)$ mass $M_{h_b(1P)}=(9899.3\pm 0.4\pm 1.0)\mathrm{MeV}/c^2$, corresponding to the hyperfine (HF) splitting $\mathrm{\Delta }{M}_{\mathrm{HF}}(1P)=(0.6\pm 0.4\pm 1.0)\mathrm{MeV}/c^2$. Using the transition $h_b(1P)\to \gamma {\eta }_b(1S)$, we measure the ${\eta }_b(1S)$ mass $M_{{\eta }_b(1S)}=(9400.7\pm 1.7\pm 1.6)\mathrm{MeV}/c^2$, corresponding to $\mathrm{\Delta }{M}_{\mathrm{HF}}(1S)=(59.6\pm 1.7\pm 1.6)\mathrm{MeV}/c^2$, the ${\eta }_b(1S)$ width ${\mathrm{\Gamma }}_{{\eta }_b(1S)}=(8_{-5}^{+6}\pm 5)\mathrm{MeV}/c^2$ and the branching fraction $\mathcal{B}[h_b(1P)\to \gamma {\eta }_b(1S)]=(56\pm 8\pm 4)\%$.

We study the interplay of geometric frustration and interactions in a nonequilibrium photonic lattice system exhibiting a polariton flat band as described by a variant of the Jaynes-Cummings-Hubbard model. We show how to engineer strong photonic correlations in such a driven, dissipative system by quenching the kinetic energy through frustration. This produces an incompressible state of photons characterized by short-ranged crystalline order with period doubling. The latter manifests itself in strong spatial correlations, i.e., on-site and nearest-neighbor antibunching combined with extended density-wave oscillations at larger distances. We propose a state-of-the-art circuit QED realization of our system, which is tunable in situ.

We report ${}^{75}\mathrm{As}$ nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on the superconductor ${\mathrm{Rb}}_2{\mathrm{Cr}}_3{\mathrm{As}}_3$ with a quasi-one-dimensional crystal structure. Below $T\sim 100\mathrm{K}$, the spin-lattice relaxation rate ($1/T_1$) divided by temperature, $1/T_{1}T$, increases upon cooling down to $T_c=4.8\mathrm{K}$, showing a Curie-Weiss-like temperature dependence. The Knight shift also increases with decreasing temperature. These results suggest ferromagnetic spin fluctuation. In the superconducting state, $1/T_1$ decreases rapidly below $T_c$ without a Hebel-Slichter peak, and follows a $T^5$ variation below $T\sim 3\mathrm{K}$, which points to unconventional superconductivity with point nodes in the gap function.

Why should achiral particles organize into a helical structure? Here, using theory and molecular dynamics simulations we show that at high concentration crescent-shaped particles interacting through a purely repulsive potential form the twist-bend nematic phase, which features helical order of the twofold symmetry axes of particles, with doubly degenerate handedness. Spontaneous breaking of the chiral symmetry is driven by the entropic gain that derives from the decrease in excluded volume in the helical arrangement. Crucial to this purpose is the concave shape of particles. This study is based on a general formulation of the Onsager theory, which includes biaxiality and polarity of phase and particles, in addition to the space modulation of order. Molecular dynamics simulations corroborate the theoretical predictions and provide further insights into the structure of the helical phase.

Thermalized chemical reactions driven under dynamical load are characteristic of activated dynamics for arbitrary nonautonomous systems. Recent generalizations of transition state theory to obtain formally exact rates have required the construction of a time-dependent transition state trajectory. Here, we show that Lagrangian descriptors can be used to obtain this structure directly. By developing a phase space separatrix that is void of recrossings, these constructs allow for the principal criterion in the implementation of modern rate theories to be satisfied. Thus, the reactive flux over a time-varying barrier can be determined without ambiguity in chemical reactions. The generality of the formalism suggests that this approach is applicable to any activated system subjected to arbitrary driving and thermal fluctuations.

We study the hydrodynamic regime of chiral plasmas at high temperature. We find a new type of gapless collective excitation induced by chiral effects in an external magnetic field. This is a transverse wave, and it is present even in incompressible fluids, unlike the chiral magnetic and chiral vortical waves. The velocity is proportional to the coefficient of the gravitational anomaly. We briefly discuss the possible relevance of this “chiral Alfvén wave” in physical systems.

The Stark effect in hydrogen and the cubic anharmonic oscillator furnish examples of quantum systems where the perturbation results in a certain ionization probability by tunneling processes. Accordingly, the perturbed ground-state energy is shifted and broadened, thus acquiring an imaginary part which is considered to be a paradigm of nonperturbative behavior. Here we demonstrate how the low order coefficients of a divergent perturbation series can be used to obtain excellent approximations to both real and imaginary parts of the perturbed ground state eigenenergy. The key is to use analytic continuation functions with a built-in singularity structure within the complex plane of the coupling constant, which is tailored by means of Bender-Wu dispersion relations. In the examples discussed the analytic continuation functions are Gauss hypergeometric functions, which take as input fourth order perturbation theory and return excellent approximations to the complex perturbed eigenvalue. These functions are Borel consistent and dramatically outperform widely used Padé and Borel-Padé approaches, even for rather large values of the coupling constant.