In a variety of superconductors, mostly in two-dimensional (2D) and one-dimensional (1D) systems, the resistive superconducting transition $R(T)$ demonstrates in many cases an anomalous narrow $R(T)$ peak just preceding the onset of the superconducting state $R=0$ at $T_c$. The amplitude of this $R(T)$ peak in 1D and 2D systems ranges from a few up to several hundred percent. In three-dimensional (3D) systems, however, the $R(T)$ peak close to $T_c$ is rarely observed, and it reaches only a few percent in amplitude. Here we report on the observation of a giant ($\sim 1600\%$) and very narrow ($\sim 1\mathrm{K}$) resistance peak preceding the onset of superconductivity in heavily boron-doped diamond. This anomalous $R(T)$ peak in a 3D system is interpreted in the framework of an empirical model based on the metal–bosonic insulator–superconductor transitions induced by a granularity-correlated disorder in heavily doped diamond.

Ever since the experiments which founded the field of highly frustrated magnetism, the kagome Heisenberg antiferromagnet has been the archetypical setting for the study of fluctuation induced exotic ordering. To this day the nature of its classical low-temperature state has remained a mystery: the nonlinear nature of the fluctuations around the exponentially numerous harmonically degenerate ground states has not permitted a controlled theory, while its complex energy landscape has precluded numerical simulations at low temperature, $T$. Here we present an efficient Monte Carlo algorithm which removes the latter obstacle. Our simulations detect a low-temperature regime in which correlations asymptote to a remarkably small value as $T\to 0$. Feeding these results into an effective model and analyzing the results in the framework of an appropriate field theory implies the presence of long-range dipolar spin order with a tripled unit cell.

Experimental measurements and ab initio modeling of the optical transitions in strained $G$-type antiferromagnetic ${\mathrm{LaCrO}}_3$ resolve two decades of debate regarding the magnitude of the band gap and the character of the optical absorption spectrum in the visible-to-ultraviolet (up to $\sim 5\mathrm{eV}$) range in this material. Using time-dependent density functional theory and accounting for thermal disorder effects, we demonstrate that the four most prominent low-energy absorption features are due to intra-Cr $t_{2g}\mathrm{\text{−}}{e}_g$ (2.7, 3.6 eV), inter-Cr $t_{2g}\mathrm{\text{−}}{t}_{2g}$ (4.4 eV), and interion O $2p$-Cr $3d$ (from $\sim 5\mathrm{eV}$) transitions and show that the excitation energies of the latter type can be strongly affected by the lattice strain.

We propose an unexplored class of absorbing materials for high-efficiency solar cells: heterostructures of transition-metal oxides. In particular, ${\mathrm{LaVO}}_3$ grown on ${\mathrm{SrTiO}}_3$ has a direct band gap $\sim 1.1\mathrm{eV}$ in the optimal range as well as an internal potential gradient, which can greatly help to separate the photogenerated electron-hole pairs. Furthermore, oxide heterostructures afford the flexibility to combine ${\mathrm{LaVO}}_3$ with other materials such as ${\mathrm{LaFeO}}_3$ in order to achieve even higher efficiencies with band-gap graded solar cells. We use density-functional theory to demonstrate these features.

The concept of cross density of states characterizes the intrinsic spatial coherence of complex photonic or plasmonic systems, independently of the illumination conditions. Using this tool and the associated intrinsic coherence length, we demonstrate unambiguously the spatial squeezing of eigenmodes on disordered fractal metallic films, thus clarifying a basic issue in plasmonics.

It is shown that the shape statistics of four correlated particles, known as a tetrad, in a direct numerical simulation of three-dimensional homogeneous isotropic turbulence agree very well with a simple diffusion equation with a separation-dependent eddy diffusivity. The latter is essentially an extension of Richardson’s model for particle-pair dispersion to tetrads. It is also shown that the degree of elongation of the tetrad in the inertial subrange of a turbulentlike flow is controlled by the exponent, $m$, in an eddy diffusivity of the form $K(r)\propto r^m$ where $r$ is the interparticle separation, becoming more elongated as $m$ increases in the range $0\le m<2$.

Spectral measurements of visible coherent transition radiation produced by a laser-plasma-accelerated electron beam are reported. The significant periodic modulations that are observed in the spectrum result from the interference of transition radiation produced by multiple bunches of electrons. A Fourier analysis of the spectral interference fringes reveals that electrons are injected and accelerated in multiple plasma wave periods, up to at least 10 periods behind the laser pulse. The bunch separation scales with the plasma wavelength when the plasma density is changed over a wide range. An analysis of the spectral fringe visibility indicates that the first bunch contains most of the charge.

New observations of the formation and dynamics of long-lived impurity-induced helical “snake” modes in tokamak plasmas have recently been carried out on Alcator C-Mod. The snakes form as an asymmetry in the impurity ion density that undergoes a seamless transition from a small helically displaced density to a large crescent-shaped helical structure inside $q<1$, with a regularly sawtoothing core. The observations show that the conditions for the formation and persistence of a snake cannot be explained by plasma pressure alone. Instead, many features arise naturally from nonlinear interactions in a 3D MHD model that separately evolves the plasma density and temperature.

We report on a numerical study of the effects of preplasma scale length and laser intensity on the hot-electron ($\ge 1\mathrm{MeV}$) divergence angle using full-scale 2D3V (two dimensional in space, three dimensional in velocity) simulations including a self-consistent laser-plasma interaction and photoionization using the particle-in-cell code LSP. Our simulations show that the fast-electron divergence angle increases approximately linearly with the preplasma scale length for a fixed laser intensity. On the other hand, for a fixed preplasma scale length, the laser intensity has little effect on the divergence angle in the range between ${10}^{18}$ and ${10}^{21}\mathrm{W}/{\mathrm{cm}}^2$. These findings have important implications for the interpretation of experimental results.

A new mechanism for intrinsic plasma flow has been experimentally identified in a toroidal plasma. For reversed field pinch plasmas with a few percent $\beta$ (ratio of plasma pressure to magnetic pressure), measurements show that parallel pressure fluctuations correlated with magnetic fluctuations create a kinetic stress that can affect momentum balance and the evolution of intrinsic plasma flow. This implies kinetic effects are important for flow generation and sustainment.

A boundary integral method is developed to investigate the effects of inner droplets and asymmetry of internal structures on rheology of two-dimensional multiple emulsion particles with arbitrary numbers of layers and droplets within each layer. Under a modest extensional flow, the number increment of layers and inner droplets, and the collision among inner droplets subject the particle to stronger shears. In addition, the coalescence or release of inner droplets changes the internal structure of the multiple emulsion particles. Since the rheology of such particles is sensitive to internal structures and their change, modeling them as the core-shell particles to obtain the viscosity equation of a single particle should be modified by introducing the time-dependable volume fraction $\Phi (t)$ of the core instead of the fixed $\Phi$. An asymmetric internal structure induces an oriented contact and merging of the outer and inner interface. The start time of the interface merging is controlled by adjusting the viscosity ratio and enhancing the asymmetry, which is promising in the controlled release of inner droplets through hydrodynamics for targeted drug delivery.

The long-standing controversy concerning the effect of electron-electron interaction on the electrical conductivity of an ideal graphene sheet is settled. Performing the calculation directly in the tight binding approach without the usual prior reduction to the massless Dirac (Weyl) theory, it is found that, to leading order in the interaction strength $\alpha =e^2/\hslash v_0$, the dc conductivity $\sigma /{\sigma }_0=1+C\alpha +O({\alpha }^2)$ is significantly enhanced with respect to the independent-electron result ${\sigma }_0$, i.e., with the value $C=0.26$. The ambiguity characterizing the various existing approaches is nontrivial and related to the chiral anomaly in the system. In order to separate the energy scales in a model with massless fermions, contributions from regions of the Brillouin zone away from the Dirac points have to be accounted for. Experimental consequences of the relatively strong interaction effect are briefly discussed.

Because of the strong spin-orbit interaction in indium antimonide, orbital motion and spin are no longer separated. This enables fast manipulation of qubit states by means of microwave electric fields. We report Rabi oscillation frequencies exceeding 100 MHz for spin-orbit qubits in InSb nanowires. Individual qubits can be selectively addressed due to intrinsic differences in their $g$ factors. Based on Ramsey fringe measurements, we extract a coherence time $T_2^{*}=8\pm 1\mathrm{ns}$ at a driving frequency of 18.65 GHz. Applying a Hahn echo sequence extends this coherence time to 34 ns.

We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25–1.2 K) and polarizing magnetic field (80–300 mT). Measurements exploit field-controlled coupling of the ensemble to two modes of a transmission-line resonator. The observed temperature-independent spin relaxation time indicates that spin outdiffusion across the mode volume dominates over spin-lattice relaxation. Depolarization of one hyperfine-split subensemble by pumping of another indicates fast cross relaxation, with implications for the use of subensembles as independent quantum memories.

We report on NMR and torque measurements on the frustrated quasi-two-dimensional spin-dimer system ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$ in magnetic fields up to 34 T that reveal a sequence of magnetization plateaus at $1/8$, $2/15$, $1/6$, and $1/4$ of the saturation and two incommensurate phases below and above the 1/6 plateau. The magnetic structures determined by NMR involve a stripe order of triplets in all plateaus, suggesting that the incommensurate phases originate from proliferation of domain walls. We propose that the magnetization process of ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$ is best described as an incomplete devil’s staircase.

We perform nonequilibrium dynamics simulations of a binary Lennard-Jones mixture in which an external force is applied on a single tagged particle. For the diffusive properties of this particle parallel to the force, superdiffusive behavior at intermediate times as well as giant long-time diffusivity is observed. A quantitative description of this nontrivial behavior is given by a continuous time random walk analysis of the system in configuration space. We further demonstrate that the same physical properties which are responsible for the superdiffusivity in nonequilibrium systems also determine the non-Gaussian parameter in equilibrium systems.

Exploration of intrachain hydrodynamics of dsDNA within channels has been limited to indirect analysis of global coil dynamics. In this Letter, we isolate hydrodynamic interactions within single molecules of dsDNA confined to slitlike channels by making use of density covariance measurements. We show that the strength of hydrodynamic interactions in DNA is dependent on the intrachain correlation length and that screening by symmetry in slitlike confinement results in a screening length that is proportional channel height. Moreover, we directly show the partial draining nature of the blobs formed by dsDNA in slits and predict under what conditions a dsDNA blob should obey nondraining Zimm behavior.

Bohmian mechanics reproduces all statistical predictions of quantum mechanics, which ensures that entanglement cannot be used for superluminal signaling. However, individual Bohmian particles can experience superluminal influences. We propose to illustrate this point using a double double-slit setup with path-entangled photons. The Bohmian velocity field for one of the photons can be measured using a recently demonstrated weak-measurement technique. The found velocities strongly depend on the value of a phase shift that is applied to the other photon, potentially at spacelike separation.

We show that universal quantum computation can be achieved in the standard pure-state circuit model while the entanglement entropy of every bipartition is small in each step of the computation. The entanglement entropy required for large-scale quantum computation even tends to zero. Moreover we show that the same conclusion applies to many entanglement measures commonly used in the literature. This includes e.g., the geometric measure, localizable entanglement, multipartite concurrence, squashed entanglement, witness-based measures, and more generally any entanglement measure which is continuous in a certain natural sense. These results demonstrate that many entanglement measures are unsuitable tools to assess the power of quantum computers.

We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of ${}^{136}\mathrm{Xe}$. We obtain a lower limit for the neutrinoless double-beta decay half-life of $T_{1/2}^{0\nu }>1.9\times {10}^{25}\mathrm{yr}$ at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give $T_{1/2}^{0\nu }>3.4\times {10}^{25}\mathrm{yr}$ at 90% C.L., which corresponds to a Majorana neutrino mass limit of $⟨m_{\beta \beta }⟩<(120–250)\mathrm{meV}$ based on a representative range of available matrix element calculations. Using those calculations, this result excludes the Majorana neutrino mass range expected from the neutrinoless double-beta decay detection claim in ${}^{76}\mathrm{Ge}$, reported by a part of the Heidelberg-Moscow Collaboration, at more than 97.5% C.L.