Neutron scattering and extensive molecular dynamics simulations of an all atom ${\mathrm{C}}_{100}{\mathrm{H}}_{202}$ system were performed to address the short-time dynamics leading to center-of-mass self-diffusion. The simulated dynamics are in excellent agreement with resolution resolved time-of-flight quasielastic neutron scattering. The anomalous subdiffusive center-of-mass motion could be modeled by explicitly accounting for viscoelastic hydrodynamic interactions. A model-free analysis of the local reorientations of the molecular backbone revealed three relaxation processes: While two relaxations characterize local bond rotation and global molecular reorientation, the third component on intermediate times could be attributed to transient flowlike motions of atoms on different molecules. The existence of these collective motions, which are clearly visualized in this Letter, strongly contribute to the chain relaxations in molecular liquids.

We consider an interferometer powered by laser light (a coherent state) into one input port and ask the following question: what is the best state to inject into the second input port, given a constraint on the mean number of photons this state can carry, in order to optimize the interferometer’s phase sensitivity? This question is the practical question for high-sensitivity interferometry. We answer the question by considering the quantum Cramér-Rao bound for such a setup. The answer is squeezed vacuum.

In recent years, invisibility cloaks have received a lot of attention and interest. These devices are generally classified into two types: passive and active. The design and realization of passive cloaks have been intensively studied using transformation optics and plasmonic approaches. However, active cloaks are still limited to theory and numerical simulations. Here, we present the first experiment on active cloaking and propose an active illusion for the Laplace equation. We make use of a resistor network to simulate a conducting medium. Then, we surround the central region with controlled sources to protect it from outside detection. We show that by dynamically changing the controlled sources, the protected region can be cloaked or disguised as different objects (illusion). Our measurement results agree very well with numerical simulations. Compared with the passive counterparts, the active cloaking and illusion devices do not need complicated metamaterials. They are flexible, in-line controllable, and adaptable to the environment. In addition to dc electricity, the proposed method can also be used for thermodynamics and other problems governed by the Laplace equation.

The heat transport mediated by near-field interactions in networks of plasmonic nanostructures is shown to be analogous to a generalized random walk process. The existence of superdiffusive regimes is demonstrated both in linear ordered chains and in three-dimensional random networks by analyzing the asymptotic behavior of the corresponding probability distribution function. We show that the spread of heat in these networks is described by a type of Lévy flight. The presence of such anomalous heat-transport regimes in plasmonic networks opens the way to the design of a new generation of composite materials able to transport heat faster than the normal diffusion process in solids.

A gyrokinetic model of ion temperature gradient driven turbulence in magnetized plasmas is used to study the injection, nonlinear redistribution, and collisional dissipation of free energy in the saturated turbulent state over a broad range of driving gradients and collision frequencies. The dimensionless parameter $L_T/L_C$, where $L_T$ is the ion temperature gradient scale length and $L_C$ is the collisional mean free path, is shown to parametrize a transition between a saturation regime dominated by nonlinear transfer of free energy to small perpendicular (to the magnetic field) scales and a regime dominated by dissipation at large scales in all phase space dimensions.

We present a systematic construction of effective Hamiltonians of periodically driven quantum systems. Because of an equivalence between the time dependence of a Hamiltonian and an interaction in its Floquet operator, flow equations, that permit us to decouple interacting quantum systems, allow us to identify time-independent Hamiltonians for driven systems. With this approach, we explain the experimentally observed deviation of expected suppression of tunneling in ultracold atoms.

We study quasi-one-dimensional few-particle systems consisting of one to six ultracold fermionic atoms in two different spin states with attractive interactions. We probe the system by deforming the trapping potential and by observing the tunneling of particles out of the trap. For even particle numbers, we observe a tunneling behavior that deviates from uncorrelated single-particle tunneling indicating the existence of pair correlations in the system. From the tunneling time scales, we infer the differences in interaction energies of systems with different number of particles, which show a strong odd-even effect, similar to the one observed for neutron separation experiments in nuclei.

Dipolaritons are mixed light-matter quasiparticles formed in double quantum wells embedded in microcavities. Because of resonant coupling between direct and indirect excitons via electronic tunneling, dipolaritons possess large dipole moments. Resonant excitation of the cavity mode by a short pulse of light induces oscillations of the indirect exciton density with a characteristic frequency of Rabi flopping. This results in oscillations of a classical Hertz dipole array which generate supperradiant emission on a terahertz (THz) frequency. The resulting THz signal may be enhanced using the supplementary THz cavity in the weak coupling regime.

We predict that plutonium hexaboride (${\mathrm{PuB}}_6$) is a strongly correlated topological insulator, with Pu in an intermediate valence state of ${\mathrm{Pu}}^{2.7+}$. Within the combination of dynamical mean field theory and density functional theory, we show that ${\mathrm{PuB}}_6$ is an insulator in the bulk, with nontrivial $Z_2$ topological invariants. Its metallic surface states have a large Fermi pocket at the $\overline{X}$ point and the Dirac cones inside the bulk derived electronic states, causing a large surface thermal conductivity. ${\mathrm{PuB}}_6$ has also a very high melting temperature; therefore, it has ideal solid state properties for a nuclear fuel material.

Although initially introduced to mimic the spin-ice pyrochlores, no artificial spin ice has yet exhibited the expected degenerate ice phase with critical correlations similar to the celebrated Coulomb phase in the pyrochlore lattice. Here we study a novel artificial spin ice based on a vertex-frustrated rather than pairwise frustrated geometry and show that it exhibits a quasicritical ice phase of extensive residual entropy and, significantly, algebraic correlations. Interesting in its own regard as a novel realization of frustration in a vertex system, our lattice opens new pathways to study defects in a critical manifold and to design degeneracy in artificial magnetic nanoarrays, a task so far elusive.

We study the effects of the internal coherent (Rabi) coupling in vortex lattices in two-component BECs under rotation. We find how the vortex lattices without the Rabi coupling known before are connected to the Abrikosov lattice of integer vortices with increasing the Rabi coupling. We find that (1) for small Rabi couplings, fractional vortices in a triangular or square lattice for small or large intercomponent coupling constitute hexamers or tetramers, namely multidimer bound states made of six or four vortices, respectively, (2) these bound states are broken into a set of dimers at intermediate Rabi couplings, and (3) vortices change their partners in various ways depending on the intercomponent coupling, to organize themselves for constituting the Abrikosov lattice of integer vortices at strong Rabi couplings.

The Alpha Magnetic Spectrometer experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter. Here, we make use of this high quality data to place stringent limits on dark matter with masses below $\sim 300\mathrm{GeV}$, annihilating or decaying to leptonic final states, essentially independent of the origin of this rise. We significantly improve on existing constraints, in some cases by up to 2 orders of magnitude.

We present a further argument that typical black holes with field theory duals have firewalls at the horizon. This argument makes no reference to entanglement between the black hole and any distant system, and so is not evaded by identifying degrees of freedom inside the black hole with those outside. We also address the $\mathrm{\text{Einstein-Rosen=Einstein-Podolsky-Rosen}}$ conjecture of Maldacena and Susskind, arguing that the correlations in generic highly entangled states cannot be geometrized as a smooth wormhole.

The ${\mathcal{D}}_{03}$ dibaryon is generated dynamically as a resonance pole in a $\pi N{\Delta }^{\prime }$ three body model, where ${\Delta }^{\prime }$ is a stable $\Delta$ baryon. Using separable interactions dominated by the $\Delta (1232)$ isobar for $\pi N$ and by the ${\mathcal{D}}_{12}(2150)$ isobar for $N{\Delta }^{\prime }$, with ${\mathcal{D}}_{12}(2150)$ the $N\Delta$ dibaryon deduced in and constrained by ${}^{1}D_2$ $pp$ scattering, the model reduces to an effective two body problem for $\Delta {\Delta }^{\prime }$ which is solved. The mass and width of ${\mathcal{D}}_{03}$ are found close to those of the $I(J^P)=0(3^{+})$ resonance peak observed by WASA-at-COSY in pion-production $pn$ collisions at 2.37 GeV.

We report the first direct measurement of transport properties of surface states in the topological insulator ${\mathrm{Bi}}_{0.91}{\mathrm{Sb}}_{0.09}$ (111) from the weak-field Hall effect and Shubnikov–de Haas oscillations. We find that the holelike surface band displays an unexpectedly high mobility $23000–85000{\mathrm{cm}}^2/\mathrm{V}\mathrm{s}$, which is the highest mobility so far reported in bismuth-based topological insulators. This result provides the first quantitative assessment of the effect of alloy disorder on the mobility of surface states in topological insulators. We show that the 9% alloy disorder decreases the mobility of surface states by a factor of less than 2.3.

The communication complexity of a quantum channel is the minimal amount of classical communication required for classically simulating the process of preparation, transmission through the channel, and subsequent measurement of a quantum state. At present, only little is known about this quantity. In this Letter, we present a procedure for systematically evaluating the communication complexity of channels in any general probabilistic theory, in particular, quantum theory. The procedure is constructive and provides the most efficient classical protocols. We illustrate this procedure by evaluating the communication complexity of a quantum depolarizing channel with some finite sets of quantum states and measurements.

We investigate the Brownian motion of boomerang colloidal particles confined between two glass plates. Our experimental observations show that the mean displacements are biased towards the center of hydrodynamic stress (CoH), and that the mean-square displacements exhibit a crossover from short-time faster to long-time slower diffusion with the short-time diffusion coefficients dependent on the points used for tracking. A model based on Langevin theory elucidates that these behaviors are ascribed to the superposition of two diffusive modes: the ellipsoidal motion of the CoH and the rotational motion of the tracking point with respect to the CoH.

We study the transport properties of a system of active particles moving at constant speed in a heterogeneous two-dimensional space. The spatial heterogeneity is modeled by a random distribution of obstacles, which the active particles avoid. Obstacle avoidance is characterized by the particle turning speed $\gamma$. We show, through simulations and analytical calculations, that the mean square displacement of particles exhibits two regimes as function of the density of obstacles ${\rho }_o$ and $\gamma$. We find that at low values of $\gamma$, particle motion is diffusive and characterized by a diffusion coefficient that displays a minimum at an intermediate obstacle density ${\rho }_o$. We observe that in high obstacle density regions and for large $\gamma$ values, spontaneous trapping of active particles occurs. We show that such trapping leads to genuine subdiffusive motion of the active particles. We indicate how these findings can be used to fabricate a filter of active particles.

Certain modified gravity theories predict the existence of an additional, nonconformally coupled scalar field. A disformal coupling of the field to the cosmic microwave background (CMB) is shown to affect the evolution of the energy density in the radiation fluid and produces a modification of the distribution function of the CMB, which vanishes if photons and baryons couple in the same way to the scalar. We find the constraints on the couplings to matter and photons coming from the measurement of the CMB temperature evolution and from current upper limits on the $\mu$ distortion of the CMB spectrum. We also point out that the measured equation of state of photons differs from $w_{\gamma }=1/3$ in the presence of disformal couplings.

The recently discovered $Z_c(3900)$ meson is a flavor-exotic tetraquark whose constituents consist of a charm quark and antiquark and a light quark and antiquark. We identify such heavy tetraquark mesons as analogs of quarkonium hybrids, with the gluon field replaced by an isospin-1 excitation of the gluon and light-quark fields. Given the identification of $Y(4260)$ as a ground-state charmonium hybrid, lattice QCD calculations of the charmonium spectrum by the Hadron Spectrum Collaboration can be used to estimate the masses of the four lowest spin-symmetry multiplets of charmonium hybrids. We make the assumption that the isospin-1 Born-Oppenheimer potentials, whose energy levels are tetraquarks, have the same shapes as the flavor-singlet Born-Oppenheimer potentials, whose energy levels are hybrids. Given the identification of $Z_c(3900)$ as a charmonium tetraquark, lattice QCD calculations of the charmonium hybrid spectrum can then be used to estimate the masses of the four lowest spin-symmetry multiplets of charmonium tetraquarks.