Structural correlations in disordered media are known to affect significantly the propagation of waves. In this Letter, we theoretically investigate the transport and localization of light in 2D photonic structures with short-range correlated disorder. The problem is tackled semianalytically using the Baus-Colot model for the structure factor of correlated media and a modified independent scattering approximation. We find that short-range correlations make it possible to easily tune the transport mean free path by more than a factor of 2 and the related localization length over several orders of magnitude. This trend is confirmed by numerical finite-difference time-domain calculations. This study therefore shows that disorder engineering can offer fine control over light transport and localization in planar geometries, which may open new opportunities in both fundamental and applied photonics research.

We study two-color high-order harmonic generation using an intense driving field and its weak second harmonic, crossed under a small angle in the focus. Employing sum- and difference-frequency generation processes, such a noncollinear scheme can be used to measure and control macroscopic phase matching effects by utilizing a geometrical phase mismatch component, which depends on the noncollinear angle. We further show how spatial phase effects in the generation volume are mapped out into the far field allowing a direct analogy with temporal carrier envelope effects in attosecond pulse generation.

Half-harmonic emission spectra and images taken during directly driven implosions show that the two-plasmon decay (TPD) instability is driven nonuniformly over the target surface and that multibeam effects dominate this instability. The images show a spatially limited extent of the TPD instability. A prominent spectral feature is used to determine the electron temperature in the corona. Near threshold the temperatures agree with one-dimensional hydrodynamic predictions but exceed them by $\sim 10\%$ above the TPD threshold. Two-dimensional hydrodynamic simulations indicate that a significant part ($\sim 20\%$) of the laser intensity must be locally absorbed by the TPD instability (i.e., by collisional damping of the electron plasma waves) to maintain these temperature islands.

We perform out-of-equilibrium molecular dynamics simulations of a monatomic liquid that exhibits liquid and glass polymorphism, with two distinct glasses, low- (LDA) and high-density (HDA) amorphous solids. By performing isobaric heating simulations of LDA and HDA at different pressures, we determine (a) the glass transition temperature of LDA and HDA, $T_g^{\mathrm{LDA}}(P)$ and $T_g^{\mathrm{HDA}}(P)$, as well as (b) the corresponding glass-glass transformation temperatures, $T_{\mathrm{LDA}\text{−}\mathrm{HDA}}(P)$ and $T_{\mathrm{HDA}\text{−}\mathrm{LDA}}(P)$. It is found that $T_g^{\mathrm{LDA}}(P)$ is anomalous; i.e., it decreases with increasing pressure, while $T_g^{\mathrm{HDA}}(P)$ increases with increasing pressure. Interestingly, the $T_g^{\mathrm{LDA}}(P)$ and $T_{\mathrm{LDA}\text{−}\mathrm{HDA}}(P)$ loci, as well as the $T_g^{\mathrm{HDA}}(P)$ and $T_{\mathrm{HDA}\text{−}\mathrm{LDA}}(P)$ loci, constitute smooth single lines in the $P-T$ plane, suggesting that heating-induced glass-glass and glass transitions are related. We discuss the present results in the context of water experiments and simulations.

Quantum-state-selective thermal desorption of ${\mathrm{H}}_2$ weakly physisorbed on Ag(111) demonstrates significantly different desorption features between the nuclear-spin modifications. An energy shift due to the rotational-symmetry breaking induced by an anisotropic interaction affects not only the enthalpy but also the entropy of adsorption. The preexponential factor for desorption of the ortho-${\mathrm{H}}_2$ is about three times as large as that of the para-${\mathrm{H}}_2$. The entropy difference indicates a perpendicular orientation preference of anisotropic physisorption potential, which also suggests the importance of partial hybridization interaction for weak physisorption.

The electronic transport experiments on topological insulators exhibit a dilemma. A negative cusp in magnetoconductivity is widely believed as a quantum transport signature of the topological surface states, which are immune from localization and exhibit the weak antilocalization. However, the measured conductivity drops logarithmically when lowering temperature, showing a typical feature of the weak localization as in ordinary disordered metals. Here, we present a conductivity formula for massless and massive Dirac fermions as a function of magnetic field and temperature, by taking into account the electron-electron interaction and quantum interference simultaneously. The formula reconciles the dilemma by explicitly clarifying that the temperature dependence of the conductivity is dominated by the interaction, while the magnetoconductivity is mainly contributed by the quantum interference. The theory paves the road to quantitatively study the transport in topological insulators, and can be extended to other two-dimensional Dirac-like systems, such as graphene, transition metal dichalcogenides, and silicene.

We report x-ray resonant magnetic scattering and resonant inelastic x-ray scattering studies of epitaxially strained ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$ thin films. The films were grown on ${\mathrm{SrTiO}}_3$ and $({\mathrm{LaAlO}}_3{)}_{0.3}({\mathrm{Sr}}_2{\mathrm{AlTaO}}_6{)}_{0.7}$ substrates, under slight tensile and compressive strains, respectively. Although the films develop a magnetic structure reminiscent of bulk ${\mathrm{Sr}}_2{\mathrm{IrO}}_4$, the magnetic correlations are extremely anisotropic, with in-plane correlation lengths significantly longer than the out-of-plane correlation lengths. In addition, the compressive (tensile) strain serves to suppress (enhance) the magnetic ordering temperature $T_N$, while raising (lowering) the energy of the zone-boundary magnon. Quantum chemical calculations show that the tuning of magnetic energy scales can be understood in terms of strain-induced changes in bond lengths.

Taking spinon excitations in the quantum antiferromagnet ${\mathrm{CaCu}}_2{\mathrm{O}}_3$ as an example, we demonstrate that femtosecond dynamics of magnetic electronic excitations can be probed by direct resonant inelastic x-ray scattering (RIXS). To this end, we isolate the contributions of single and double spin-flip excitations in experimental RIXS spectra, identify the physical mechanisms that cause them, and determine their respective time scales. By comparing theory and experiment, we find that double spin flips need a finite amount of time to be generated, rendering them sensitive to the core-hole lifetime, whereas single spin flips are, to a very good approximation, independent of it. This shows that RIXS can grant access to time-domain dynamics of excitations and illustrates how RIXS experiments can distinguish between excitations in correlated electron systems based on their different time dependence.

Using a first-principles-based effective Hamiltonian within molecular dynamics simulations, we discover that applying an electric field that is opposite to the initial direction of the polarization results in a switching of both the polarization and the magnetic chirality vector of multiferroic ${\mathrm{BiFeO}}_3$ at an ultrafast pace (namely, of the order of picoseconds). We discuss the origin of such a double ultrafast switching, which is found to involve original intermediate magnetic states and may hold promise for designing various devices.

Much recent effort has focused on glassy and jamming properties of spherical particles. Very little is known about such phenomena for nonspherical particles, and we take a first step by studying ellipses. We find important differences between the dynamical and structural properties of disks and two-dimensional ellipses subject to continuous Couette shear. In particular, ellipses show slow dynamical evolution, without a counterpart in disks, in the mean velocity, local density, orientational order, and local stress. Starting from an unjammed state, ellipses can first jam under shear, and then slowly unjam. The slow unjamming process is understood as a result of gradual changes in their orientations, leading to a denser packing. For disks, the rotation of particles only contributes to the relaxation of frictional forces, and hence, does not significantly cause structural changes. For the shear-jammed states, the global building up and relaxation of stress, which occurs in the form of stress avalanches, is qualitatively different for disks and ellipses, and is manifested by different forms of rate dependence for ellipses versus disks. Unlike the weak rate dependence typical for many granular systems, ellipses show power-law dependence on the shearing rate $\mathrm{\Omega }$.

Machines are only Carnot efficient if they are reversible, but then their power output is vanishingly small. Here we ask, what is the maximum efficiency of an irreversible device with finite power output? We use a nonlinear scattering theory to answer this question for thermoelectric quantum systems, heat engines or refrigerators consisting of nanostructures or molecules that exhibit a Peltier effect. We find that quantum mechanics places an upper bound on both power output and on the efficiency at any finite power. The upper bound on efficiency equals Carnot efficiency at zero power output but decays with increasing power output. It is intrinsically quantum (wavelength dependent), unlike Carnot efficiency. This maximum efficiency occurs when the system lets through all particles in a certain energy window, but none at other energies. A physical implementation of this is discussed, as is the suppression of efficiency by a phonon heat flow.

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension $G\mu$ below ${10}^{-8}$ in some regions of the cosmic string parameter space.

We give a unified description of $D=3$ super-Yang-Mills theory with $\mathcal{N}=1$, 2, 4, and 8 supersymmeties in terms of the four division algebras: reals ($\mathbb{R}$), complexes ($\mathbb{C}$), quaternions ($\mathbb{H}$) and octonions ($\mathbb{O}$). Tensoring left and right super-Yang-Mills multiplets with $\mathcal{N}=1$, 2, 4, 8 we obtain a magic square $\mathbb{R}\mathbb{R}$, $\mathbb{C}\mathbb{R}$, $\mathbb{C}\mathbb{C}$, $\mathbb{H}\mathbb{R}$, $\mathbb{H}\mathbb{C}$, $\mathbb{H}\mathbb{H}$, $\mathbb{O}\mathbb{R}$, $\mathbb{O}\mathbb{C}$, $\mathbb{O}\mathbb{H}$, $\mathbb{O}\mathbb{O}$ description of $D=3$ supergravity with $\mathcal{N}=2$, 3, 4, 5, 6, 8, 9, 10, 12, 16.

A search for the dinucleon decay $pp\to K^{+}{K}^{+}$ has been performed using $91.6\mathrm{kton}·\text{yr}$ data from Super-Kamiokande-I. This decay provides a sensitive probe of the $R$-parity-violating parameter ${{\lambda }_{112}}^{\prime \prime }$. A boosted decision tree analysis found no signal candidates in the data. The expected background was $0.28\pm 0.19$ atmospheric neutrino induced events and the estimated signal detection efficiency was $12.6\%\pm 3.2\%$. A lower limit of $1.7\times {10}^{32}\text{years}$ has been placed on the partial lifetime of the decay ${}^{16}\mathrm{O}\to {}^{14}\mathrm{C}{K}^{+}{K}^{+}$ at 90% C.L. A corresponding upper limit of $7.8\times {10}^{-9}$ has been placed on the parameter ${{\lambda }_{112}}^{\prime \prime }$.

We report on the first observation of the unbound proton-rich nucleus ${}^{15}\mathrm{Ne}$. Its ground state and first excited state were populated in two-neutron knockout reactions from a beam of 500 MeV/u ${}^{17}\mathrm{Ne}$. The ${}^{15}\mathrm{Ne}$ ground state is found to be unbound by 2.522(66) MeV. The decay proceeds directly to ${}^{13}\mathrm{O}$ with simultaneous two-proton emission. No evidence for sequential decay via the energetically allowed $2^{-}$ and $1^{-}$ states in ${}^{14}\mathrm{F}$ is observed. The ${}^{15}\mathrm{Ne}$ ground state is shown to have a strong configuration with two protons in the ($sd$) shell around ${}^{13}\mathrm{O}$ with a 63(5)% $(1s_{1/2}{)}^2$ component.

The charge form factor of ${}^4\mathrm{He}$ has been extracted in the range $29{\mathrm{fm}}^{-2}\le Q^2\le 77{\mathrm{fm}}^{-2}$ from elastic electron scattering, detecting ${}^4\mathrm{He}$ recoil nuclei and electrons in coincidence with the high resolution spectrometers of the Hall A Facility of Jefferson Lab. The measurements have uncovered a second diffraction minimum for the form factor, which was predicted in the $Q^2$ range of this experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the few-body problem.

We present a purely classical recollision scenario, i.e., without tunneling, which, in contrast to the standard three-step model, takes into account the ionic core potential fully at all stages of the recollision process and is valid at all intensities. We find that a key periodic orbit drives the recollisions by guiding electrons away and back to the core. At sufficiently high intensity, we connect our scenario to the three-step model, and explain why the three-step model leads to good agreement with the cutoff in high harmonic generation despite neglecting the core potential after tunneling.

We propose a general framework to effectively “open” a high-$Q$ resonator, that is, to release the quantum state initially prepared in it in the form of a traveling electromagnetic wave. This is achieved by employing a mediating mode that scatters coherently the radiation from the resonator into a one-dimensional continuum of modes such as a waveguide. The same mechanism may be used to “feed” a desired quantum field to an initially empty cavity. Switching between an open and “closed” resonator may then be obtained by controlling either the detuning of the scatterer or the amount of time it spends in the resonator. First, we introduce the model in its general form, identifying (i) the traveling mode that optimally retains the full quantum information of the resonator field and (ii) a suitable figure of merit that we study analytically in terms of the system parameters. Then, we discuss two feasible implementations based on ensembles of two-level atoms interacting with cavity fields. In addition, we discuss how to integrate traditional cavity QED in our proposal using three-level atoms.

We study the interaction of two photons in a Rydberg atomic ensemble under the condition of electromagnetically induced transparency, combining a semiclassical approach for pulse propagation and a complete quantum treatment for quantum state evolution. We find that the blockade regime is not suitable for implementing photon-photon cross-phase modulation due to pulse absorption and dispersion. However, approximately ideal cross-phase modulation can be realized based on relatively weak interactions, with counterpropagating and transversely separated pulses.

We describe a new kind of phase-preserving quantum amplifier which utilizes dissipative interactions in a parametrically coupled three-mode bosonic system. The use of dissipative interactions provides a fundamental advantage over standard cavity-based parametric amplifiers: large photon number gains are possible with quantum-limited added noise, with no limitation on the gain-bandwidth product. We show that the scheme is simple enough to be implemented both in optomechanical systems and in superconducting microwave circuits.