Experiments with cold atoms explore the low temperature superfluid phase transition of paired fermions in two dimensions.

[Phys. Rev. Lett. 115, 010401] Published Tue Jun 30, 2015

]]>Scientists have now enlisted atomic spectroscopy in the hunt for dark matter.

[Phys. Rev. Lett. 115, 011802] Published Tue Jun 30, 2015

]]>We show that microwave spectroscopy of a dense Rydberg gas trapped on a superconducting atom chip in the dipole blockade regime reveals directly the dipole-dipole many-body interaction energy spectrum. We use this method to investigate the expansion of the Rydberg cloud under the effect of repulsive…

[Phys. Rev. Lett. 115, 013001] Published Tue Jun 30, 2015

]]>We demonstrate ground-state cooling of a trapped ion using radio-frequency (rf) radiation. This is a powerful tool for the implementation of quantum operations, where rf or microwave radiation instead of lasers is used for motional quantum state engineering. We measure a mean phonon number of $\overline{n}=\mathrm{0.1\dots}$

[Phys. Rev. Lett. 115, 013002] Published Tue Jun 30, 2015

]]>We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time de…

[Phys. Rev. Lett. 115, 014801] Published Tue Jun 30, 2015

]]>We derive that lightning can start if the electric field is 15% of the breakdown field, and if elongated ice particles of 6 cm length and 100 free electrons per ${\mathrm{cm}}^{3}$ are present. This is one particular example set from a parameter range that we discuss as well. Our simulations include the permittivit…

[Phys. Rev. Lett. 115, 015002] Published Tue Jun 30, 2015

]]>On periodic superhydrophobic surfaces the receding contact angle often scales with the surface fraction, as expected from a simple rule of mixture, the Cassie relation. However, it has been argued that energy averaging breaks down owing to line pinning, and that line fraction scaling should apply in…

[Phys. Rev. Lett. 115, 016101] Published Tue Jun 30, 2015

]]>The complex behavior of photoemission in topological insulators is a result of quantum interference involving three photoemission channels according to $a\phantom{\rule{0}{0ex}}b\phantom{\rule{0.333em}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations.

[Phys. Rev. Lett. 115, 016801] Published Tue Jun 30, 2015

]]>[Phys. Rev. Lett. 115, 019901] Published Tue Jun 30, 2015

]]>Spatial variations in the distribution of galaxy luminosities, estimated from redshifts as distance proxies, are correlated with the peculiar velocity field. Comparing these variations with the peculiar velocities inferred from galaxy redshift surveys is a powerful test of gravity and dark-energy th…

[Phys. Rev. Lett. 115, 011301] Published Mon Jun 29, 2015

]]>It is shown that in extensions of the standard model of quarks and leptons where the additive lepton number $L$ is broken by two units, so that ${Z}_{2}$ lepton parity, i.e., $(-1{)}^{L}$ which is either even or odd, remains exactly conserved, there is the possibility of stable dark matter without additional symmet…

[Phys. Rev. Lett. 115, 011801] Published Mon Jun 29, 2015

]]>The plasma of quarks and gluons that forms when a proton collides with a lead nucleus has unexpected liquid-like properties.

[Phys. Rev. Lett. 115, 012301] Published Mon Jun 29, 2015

]]>An energy-channeling mechanism is proposed to explain flattening of the electron temperature profiles at a high beam power in the beam-heated National Spherical Torus Experiment (NSTX). Results of self-consistent simulations of neutral-beam-driven compressional Alfvén eigenmodes (CAEs) in NSTX are p…

[Phys. Rev. Lett. 115, 015001] Published Mon Jun 29, 2015

]]>By means of *ab initio* calculations combined to statistical mechanics, we provide new evidence that an experimentally undetectable tiny amount of impurities can be responsible for drastic changes in vacancy concentrations ([$V$]), inducing large deviations from an Arrhenius law even at low temperature.…

[Phys. Rev. Lett. 115, 015501] Published Mon Jun 29, 2015

]]>We numerically investigate the surface states of a strong topological insulator in the presence of strong electron-electron interactions. We choose a spherical topological insulator geometry to make the surface amenable to a finite size analysis. The single-particle problem maps to that of Landau or…

[Phys. Rev. Lett. 115, 017001] Published Mon Jun 29, 2015

]]>We investigate experimentally the synchronization of vortex based spin transfer nano-oscillators to an external rf current whose frequency is at multiple integers, as well as at an integer fraction, of the oscillator frequency. Through a theoretical study of the locking mechanism, we highlight the c…

[Phys. Rev. Lett. 115, 017201] Published Mon Jun 29, 2015

]]>We realize a quantum-compatible multimode interaction in an ultrahigh $Q$ mechanical resonator via a reservoir-mediated parametric coupling. We use this interaction to demonstrate nondegenerate parametric amplification and thermomechanical noise squeezing, finding excellent agreement with a theoretica…

[Phys. Rev. Lett. 115, 017202] Published Mon Jun 29, 2015

]]>We study the statistical force of a nonequilibrium environment on a quasistatic probe. In the linear regime, the isothermal work on the probe equals the excess work for the medium to relax to its new steady condition with a displaced probe. Also, the relative importance of reaction paths can be meas…

[Phys. Rev. Lett. 114, 250601] Published Fri Jun 26, 2015

]]>Particles orbiting near a spinning black hole might collide and get ejected with much more energy than previous calculations showed.

[Phys. Rev. Lett. 114, 251103] Published Fri Jun 26, 2015

]]>Four-dimensional asymptotically free large $N$ gauge theories compactified on ${S}_{R}^{3}\times \mathbb{R}$ have a weakly coupled confining regime when $R$ is small compared to the strong scale. We compute the vacuum energy of a variety of confining large $N$ nonsupersymmetric gauge theories in this calculable regime, where the …

[Phys. Rev. Lett. 114, 251604] Published Fri Jun 26, 2015

]]>A possible signature of chiral symmetry restoration, in the form of a chiral magnetic wave in the quark-gluon plasma, has been observed in heavy-ion collisions at RHIC.

[Phys. Rev. Lett. 114, 252302] Published Fri Jun 26, 2015

]]>We demonstrate $\mathcal{P}\mathcal{T}$-symmetry-breaking chaos in an optomechanical system, which features an ultralow driving threshold. In principle, this chaos will emerge once a driving laser is applied to the cavity mode and lasts for a period of time. The driving strength is inversely proportional to the starting …

[Phys. Rev. Lett. 114, 253601] Published Fri Jun 26, 2015

]]>Alpha particles would need to provide 50 kJ of heating to achieve a burning plasma regime - where more energy is released by the fusion reactions than is absorbed by the fuel - at the National Ignition Facility.

[Phys. Rev. Lett. 114, 255003] Published Fri Jun 26, 2015

]]>A harmonically trapped atomic gas can transition from a BKT superfluid to a Bose-Einstein condensate by reducing the interaction strength between the atoms.

[Phys. Rev. Lett. 114, 255302] Published Fri Jun 26, 2015

]]>RNA is highly sensitive to the ionic environment and typically requires ${\mathrm{Mg}}^{2+}$ to form compact structures. There is a need for models capable of describing the ion atmosphere surrounding RNA with quantitative accuracy. We present a model of RNA electrostatics and apply it within coarse-grained molecul…

[Phys. Rev. Lett. 114, 258105] Published Fri Jun 26, 2015

]]>[Phys. Rev. Lett. 114, 259901] Published Fri Jun 26, 2015

]]>Neutrons produced by the carbon fusion reaction ${}^{12}\mathrm{C}({}^{12}\mathrm{C},n){}^{23}\mathrm{Mg}$ play an important role in stellar nucleosynthesis. However, past studies have shown large discrepancies between experimental data and theory, leading to an uncertain cross section extrapolation at astrophysical energies. We present the f…

[Phys. Rev. Lett. 114, 251102] Published Thu Jun 25, 2015

]]>The low-lying structure of the neutron-rich nucleus ${}^{50}\mathrm{Ar}$ has been investigated at the Radioactive Isotope Beam Factory using in-beam $\gamma $-ray spectroscopy with ${}^{9}\mathrm{Be}({}^{54}\mathrm{Ca},{}^{50}\mathrm{Ar}+\gamma )X$, ${}^{9}\mathrm{Be}({}^{55}\mathrm{Sc},{}^{50}\mathrm{Ar}+\gamma )X$, and ${}^{9}\mathrm{Be}({}^{56}\mathrm{Ti},{}^{50}\mathrm{Ar}+\gamma )X$ multinucleon removal reactions at $\sim 220\text{\hspace{0.17em}\hspace{0.17em}}\mathrm{MeV}/\mathrm{u}$. A $\gamma $-ray peak at 1178(18) keV is repo…

[Phys. Rev. Lett. 114, 252501] Published Thu Jun 25, 2015

]]>We report the observation of coherent heteronuclear spin dynamics driven by interspecies spin-spin interaction in an ultracold spinor mixture, which manifests as periodical and well-correlated spin oscillations between two atomic species. In particular, we investigate the magnetic field dependence o…

[Phys. Rev. Lett. 114, 255301] Published Thu Jun 25, 2015

]]>We report on the use of helium ion implantation to independently control the out-of-plane lattice constant in epitaxial ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ thin films without changing the in-plane lattice constants. The process is reversible by a vacuum anneal. Resistance and magnetization measurements show that even a …

[Phys. Rev. Lett. 114, 256801] Published Thu Jun 25, 2015

]]>The electronic phase diagram of the weak spin-orbit Mott insulator (${\mathrm{Sr}}_{1-x}{\mathrm{La}}_{x}{)}_{3}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antifer…

[Phys. Rev. Lett. 114, 257203] Published Thu Jun 25, 2015

]]>The macroscopic emergent behavior of social animal groups is a classic example of dynamical self-organization, and is thought to arise from the local interactions between individuals. Determining these interactions from empirical data sets of real animal groups, however, is challenging. Using multic…

[Phys. Rev. Lett. 114, 258103] Published Thu Jun 25, 2015

]]>Swimming bacteria display a remarkable tendency to move along flat surfaces for prolonged times. This behavior may have a biological importance but can also be exploited by using microfabricated structures to manipulate bacteria. The main physical mechanism behind the surface entrapment of swimming …

[Phys. Rev. Lett. 114, 258104] Published Thu Jun 25, 2015

]]>Confined liquids organize in solidlike layers at the liquid-substrate interface. Here we use force-clamp spectroscopy AFM to capture the equilibrium dynamics between the broken and reformed states of an individual solvation layer in real time. Kinetic measurements demonstrate that the rupture of eac…

[Phys. Rev. Lett. 114, 258303] Published Thu Jun 25, 2015

]]>We solve the problem of whether a set of quantum tests reveals state-independent contextuality and use this result to identify the simplest set of the minimal dimension. We also show that identifying state-independent contextuality graphs [R. Ramanathan and P. Horodecki, Phys. Rev. Lett. **112**, 040404…

[Phys. Rev. Lett. 114, 250402] Published Wed Jun 24, 2015

]]>We present a general framework for contextuality tests in phase space using displacement operators. First, we derive a general condition that a single-mode displacement operator should fulfill in order to construct Peres-Mermin square and similar scenarios. This approach offers a straightforward sch…

[Phys. Rev. Lett. 114, 250403] Published Wed Jun 24, 2015

]]>Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be in…

[Phys. Rev. Lett. 114, 251101] Published Wed Jun 24, 2015

]]>In analogy with crystalline solids around us, Wilczek recently proposed the idea of “time crystals” as phases that spontaneously break the continuous time translation into a discrete subgroup. The proposal stimulated further studies and vigorous debates whether it can be realized in a physical syste…

[Phys. Rev. Lett. 114, 251603] Published Wed Jun 24, 2015

]]>Gapped 2D Dirac materials, in which inversion symmetry is broken by a gap-opening perturbation, feature a unique valley transport regime. Topological valley currents in such materials are dominated by bulk currents produced by electronic states just beneath the gap rather than by edge modes. The sys…

[Phys. Rev. Lett. 114, 256601] Published Wed Jun 24, 2015

]]>The three dimensional topological insulator bismuth selenide (${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$) is expected to possess strong spin-orbit coupling and spin-textured topological surface states and, thus, exhibit a high charge to spin current conversion efficiency. We evaluate spin-orbit torques in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}/{\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$ devices at…

[Phys. Rev. Lett. 114, 257202] Published Wed Jun 24, 2015

]]>We present molecular dynamics simulations of polymer-nanoparticle blends in films containing both grafted and ungrafted nanoparticles where the particle cores are identical and grafted chains are similar to a matrix polymer. Our results indicate that it is possible to control the location of bare na…

[Phys. Rev. Lett. 114, 258301] Published Wed Jun 24, 2015

]]>Colloidal gels are out-of-equilibrium structures, made up of a rarefied network of colloidal particles. Comparing experiments to numerical simulations, with hydrodynamic interactions switched off, we demonstrate the crucial role of the solvent for gelation. Hydrodynamic interactions suppress the for…

[Phys. Rev. Lett. 114, 258302] Published Wed Jun 24, 2015

]]>We initiate the study of equilibration rates of strongly coupled quark-gluon plasmas in the absence of conformal symmetry. We primarily consider a supersymmetric mass deformation within $\mathcal{N}={2}^{*}$ gauge theory and use holography to compute quasinormal modes of a variety of scalar operators, as well as the…

[Phys. Rev. Lett. 114, 251601] Published Tue Jun 23, 2015

]]>A quantum gravity holographic model can describe strongly correlated systems, in particular polaron quasiparticles, predicting a metal-insulator transition.

[Phys. Rev. Lett. 114, 251602] Published Tue Jun 23, 2015

]]>The dynamics of topological domains which break parity ($\mathcal{P}$) and charge-parity ($\mathcal{C}\mathcal{P}$) symmetry of QCD are studied. We derive in a general setting that those local domains will generate an axial current and quantify the strength of the induced axial current. Our findings are verified in a top-down hologr…

[Phys. Rev. Lett. 114, 252301] Published Tue Jun 23, 2015

]]>We report the results of a direct search for the ${}^{229}\mathrm{Th}$ (${I}^{\pi}=3/{2}^{+}\leftarrow 5/{2}^{+}$) nuclear isomeric transition, performed by exposing ${}^{229}\mathrm{Th}$-doped ${\mathrm{LiSrAlF}}_{6}$ crystals to tunable vacuum-ultraviolet synchrotron radiation and observing any resulting fluorescence. We also use existing nuclear physics data to establish …

[Phys. Rev. Lett. 114, 253001] Published Tue Jun 23, 2015

]]>It is shown, by simulation and theory, that circularly or elliptically polarized terahertz radiation can be generated when a static magnetic ($B$) field is imposed on a gas target along the propagation direction of a two-color laser driver. The radiation frequency is determined by $\sqrt{{\omega}_{p}^{2}+{\omega}_{c}^{2}/4}+{\omega}_{c}/2$, wher…

[Phys. Rev. Lett. 114, 253901] Published Tue Jun 23, 2015

]]>Crystals doped with rare-earth ions, and cooled to 4 K, can be optically pumped so that they are transparent over narrow frequency ranges. Using these crystals as spectral windows could allow for reliable, long-term laser frequency stabilization.

[Phys. Rev. Lett. 114, 253902] Published Tue Jun 23, 2015

]]>A new electron beam splitter that fits on a millimeter-sized chip could allow quantum optics experiments with free electrons.

[Phys. Rev. Lett. 114, 254801] Published Tue Jun 23, 2015

]]>Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime …

[Phys. Rev. Lett. 114, 255001] Published Tue Jun 23, 2015

]]>Multiscale gyrokinetic turbulence simulations with the real ion-to-electron mass ratio and $\beta $ value are realized for the first time, where the $\beta $ value is given by the ratio of plasma pressure to magnetic pressure and characterizes electromagnetic effects on microinstabilities. Numerical analysis at b…

[Phys. Rev. Lett. 114, 255002] Published Tue Jun 23, 2015

]]>We determine the dynamical critical exponent $z$ appearing at the Bose glass to superfluid transition in two dimensions by performing large scale numerical studies of *two* microscopically different quantum models within the universality class: The hard-core boson model and the quantum rotor (soft core)…

[Phys. Rev. Lett. 114, 255701] Published Tue Jun 23, 2015

]]>Topological-crystalline-insulators and strong-topological-insulator phases of matter can be present in a single system. This is demonstrated using photoelectron spectroscopy measurements and band structure calculations.

[Phys. Rev. Lett. 114, 256401] Published Tue Jun 23, 2015

]]>We present a microscopic derivation of the nematic charge-density wave (CDW) formation in cuprate superconductors based on the three-orbital $d\text{\u2212}p$ Hubbard model by introducing the vertex correction (VC) into the charge susceptibility. The CDW instability at $\mathit{q}=({\mathrm{\Delta}}_{\text{FS}},0)$, $(0,{\mathrm{\Delta}}_{\text{FS}})$ appears when the spin flu…

[Phys. Rev. Lett. 114, 257001] Published Tue Jun 23, 2015

]]>In disordered Weyl semimetals, mechanisms of topological origin lead to the protection against Anderson localization, and at the same time to different types of transverse electromagnetic response—the anomalous Hall and the chiral magnetic effect. We here apply field theory methods to discuss the ma…

[Phys. Rev. Lett. 114, 257201] Published Tue Jun 23, 2015

]]>Individual birds flying in a flock do not fly in straight lines, but weave in and out of each other. Topological invariant braiding statistics shows that this weaving has a coherent rotation: the birds create a braid.

[Phys. Rev. Lett. 114, 258101] Published Tue Jun 23, 2015

]]>The microscopic stress field provides a unique connection between atomistic simulations and mechanics at the nanoscale. However, its definition remains ambiguous. Rather than a mere theoretical preoccupation, we show that this fact acutely manifests itself in local stress calculations of defective g…

[Phys. Rev. Lett. 114, 258102] Published Tue Jun 23, 2015

]]>We investigate the trade-off between information gain and disturbance for von Neumann measurements on spin-$\frac{1}{2}$ particles, and derive the measurement pointer state that saturates this trade-off, which turns out to be highly unusual. We apply this result to the question of whether the nonlocality of a …

[Phys. Rev. Lett. 114, 250401] Published Mon Jun 22, 2015

]]>Femtosecond x-ray pulses image structural changes in a molecule.

[Phys. Rev. Lett. 114, 255501] Published Mon Jun 22, 2015

]]>We elaborate an *ab initio* approach for the evaluation of the one-loop quantum electrodynamical corrections to energy levels of diatomic quasimolecules. The approach accounts for the interaction between an electron and two nuclei in all orders in $Z\alpha $ and can be applied for a wide range of internuclear…

[Phys. Rev. Lett. 114, 243004] Published Fri Jun 19, 2015

]]>A new technique in atomic force microscopy more accurately measures the electrostatic force between the probe and the surface.

[Phys. Rev. Lett. 114, 246102] Published Fri Jun 19, 2015

]]>Using x-ray scattering, spectroscopy, and density-functional theory, we determine the structure of the oxidation front when a ${\mathrm{UO}}_{2}$ (111) surface is exposed to oxygen at ambient conditions. In contrast to classical diffusion and previously reported bulk ${\mathrm{UO}}_{2+x}$ structures, we find oxygen interstitials o…

[Phys. Rev. Lett. 114, 246103] Published Fri Jun 19, 2015

]]>${\mathrm{CeRhIn}}_{5}$ is an itinerant magnet where the ${\mathrm{Ce}}^{3+}$ spins order in a simple helical phase. We investigate the spin excitations and observe sharp spin waves parameterized by a nearest-neighbor exchange, ${J}_{\mathrm{RKKY}}=0.88\pm 0.05\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{meV}$. At higher energies, the spin fluctuations are heavily damped, where single-quasipa…

[Phys. Rev. Lett. 114, 247005] Published Fri Jun 19, 2015

]]>Magnetic control of the crystal chirality was announced by Saito *et al.* [Phys. Rev. Lett. **101**, (2008)] on the ground of experiments in $\mathrm{Cu}{\mathrm{B}}_{2}{\mathrm{O}}_{4}$. This claim has raised a sharp dispute in the literature because it seemed to contradict the fundamental symmetry principles. We settle this dispute on the b…

[Phys. Rev. Lett. 114, 247210] Published Fri Jun 19, 2015

]]>We provide a microscopic theory for semiconductor quantum dots that explains the pronounced deviations from the prevalent point-dipole description that were recently observed in spectroscopic experiments on quantum dots in photonic nanostructures. The deviations originate from structural inhomogenei…

[Phys. Rev. Lett. 114, 247401] Published Fri Jun 19, 2015

]]>Atoms in a condensate could be used to image the quantum wave function of an impurity charge.

[Phys. Rev. Lett. 114, 243003] Published Thu Jun 18, 2015

]]>We propose a self-similar kinetic theory of thermal conductivity in a magnetized plasma, and discuss its application to the solar wind. We study a collisional kinetic equation in a spatially expanding magnetic flux tube, assuming that the magnetic field strength, the plasma density, and the plasma t…

[Phys. Rev. Lett. 114, 245003] Published Thu Jun 18, 2015

]]>Bad-metal (BM) behavior featuring linear temperature dependence of the resistivity extending to well above the Mott-Ioffe-Regel (MIR) limit is often viewed as one of the key unresolved signatures of strong correlation. Here we associate the BM behavior with the Mott quantum criticality by examining …

[Phys. Rev. Lett. 114, 246402] Published Thu Jun 18, 2015

]]>The two-dimensional Affleck-Kennedy-Lieb-Tasaki (AKLT) model on a honeycomb lattice has been shown to be a universal resource for quantum computation. In this valence bond solid, however, the spin interactions involve higher powers of the Heisenberg coupling $({\overrightarrow{S}}_{i}\xb7{\overrightarrow{S}}_{j}{)}^{n}$, making these states seemingly…

[Phys. Rev. Lett. 114, 247204] Published Thu Jun 18, 2015

]]>We investigate magnetic order in a lattice of classical spins coupled to an isotropic gas of one-dimensional conduction electrons via local exchange interactions. The frequently discussed Ruderman-Kittel-Kasuya-Yosida effective exchange model for this system predicts that spiral order is always pref…

[Phys. Rev. Lett. 114, 247205] Published Thu Jun 18, 2015

]]>The channeling of spin waves with domain walls in ultrathin ferromagnetic films is demonstrated theoretically and through micromagnetics simulations. It is shown that propagating excitations localized to the wall, which appear in the frequency gap of bulk spin wave modes, can be guided in curved geo…

[Phys. Rev. Lett. 114, 247206] Published Thu Jun 18, 2015

]]>It is a salient experimental fact that a large fraction of candidate spin liquid materials freeze as the temperature is lowered. The question naturally arises whether such freezing is intrinsic to the spin liquid (“disorder-free glassiness”) or extrinsic, in the sense that a topological phase simply…

[Phys. Rev. Lett. 114, 247207] Published Thu Jun 18, 2015

]]>Marginal stability is the notion that stability is achieved, but only barely so. This property constrains the ensemble of configurations explored at low temperature in a variety of systems, including spin, electron, and structural glasses. A key feature of marginal states is a (saturated) pseudogap …

[Phys. Rev. Lett. 114, 247208] Published Thu Jun 18, 2015

]]>The magnetic ordering temperature of complex iridates decreases as SrTiO${}_{3}$ spacer layers are inserted between perovskite SrIrO${}_{3}$ layers. At a crticial number of spacers the material transitions from an insulator to a semimetal.

[Phys. Rev. Lett. 114, 247209] Published Thu Jun 18, 2015

]]>Two-dimensional (2D) atom lattices provide model setups with Coulomb correlations that induce competing ground states. Here, SiC emerges as a wide-gap substrate with reduced screening. We report the first artificial high-$Z$ atom lattice on SiC(0001) by Sn adatoms, based on experimental realization an…

[Phys. Rev. Lett. 114, 247602] Published Thu Jun 18, 2015

]]>We devise a cold-atom approach to realizing a broad range of bilinear quantum magnets. Our scheme is based on off-resonant single-photon excitation of Rydberg $P$ states (Rydberg dressing), whose strong interactions are shown to yield controllable $XYZ$ interactions between effective spins, represented …

[Phys. Rev. Lett. 114, 243002] Published Wed Jun 17, 2015

]]>Precise measurements are performed on spectral line shapes of spontaneous Rayleigh-Brillouin scattering in mixtures of the noble gases Ar and Kr, with He. Admixture of a light He atomic fraction results in marked changes of the spectra, although in all experiments He is merely a spectator atom: it a…

[Phys. Rev. Lett. 114, 243902] Published Wed Jun 17, 2015

]]>Edge intrinsic rotation was investigated in Ohmic $L$-mode discharges on the Tokamak à Configuration Variable, scanning the major radial position of the $X$ point, ${R}_{X}$. Edge rotation decreased linearly with increasing ${R}_{X}$, vanishing or becoming countercurrent for an outboard $X$ point, in agreement with the…

[Phys. Rev. Lett. 114, 245001] Published Wed Jun 17, 2015

]]>Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Here, we report on the first l…

[Phys. Rev. Lett. 114, 245002] Published Wed Jun 17, 2015

]]>We show that the critical velocity of a superfluid flow through a penetrable barrier coincides with the onset of the analog black-hole lasing effect. This dynamical instability is triggered by modes resonating in an effective cavity formed by two horizons enclosing the barrier. The location of the h…

[Phys. Rev. Lett. 114, 245301] Published Wed Jun 17, 2015

]]>Using x-ray photoelectron spectroscopy we observe the breaking of the strong interatomic bond in molecular CO at low temperature on a stepped Cu surface. Since the electronic structure of Cu does not allow for the splitting of CO at such low temperatures it suggests that there may be a less obvious …

[Phys. Rev. Lett. 114, 246101] Published Wed Jun 17, 2015

]]>Circularly polarized light opens a gap in the Dirac spectrum of graphene and topological insulator (TI) surfaces, thereby inducing a quantum Hall-like phase. We propose to detect the accompanying edge states and their current by the magnetic field they produce. The topological nature of the edge sta…

[Phys. Rev. Lett. 114, 246802] Published Wed Jun 17, 2015

]]>The superconducting properties of ${\mathrm{LaFeAsO}}_{1-x}{\mathrm{F}}_{x}$ under conditions of optimal electron doping are investigated upon the application of external pressure up to $\sim 23\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{kbar}$. Measurements of muon-spin spectroscopy and dc magnetometry evidence a clear mutual independence between the critical temperature ${T}_{c}$ a…

[Phys. Rev. Lett. 114, 247004] Published Wed Jun 17, 2015

]]>A first-principles investigation into the magnetic ferroelectric ${\mathrm{PbTi}}_{1-x}{\mathrm{Co}}_{x}{\mathrm{O}}_{3}$ has revealed a bi-stable magnetic system with strong spin-lattice coupling. The local distortions induced by the low-spin to high-spin crossover are ferroelectric in nature, and are characterized by the displacement of the…

[Phys. Rev. Lett. 114, 247601] Published Wed Jun 17, 2015

]]>An optical technique polarizes the spin of nuclei in silicon carbide, offering a potential new route to nuclear spin-based quantum memory.

[Phys. Rev. Lett. 114, 247603] Published Wed Jun 17, 2015

]]>Unitary transformations are the most general input-output maps available in closed quantum systems. Good control protocols have been developed for qubits, but questions remain about the use of optimal control theory to design unitary maps in high-dimensional Hilbert spaces, and about the feasibility…

[Phys. Rev. Lett. 114, 240401] Published Tue Jun 16, 2015

]]>The most sensitive limits on dark matter annihilation rate could be obtained by cross-correlating $\gamma $-ray emission from dark matter with their gravitational fingerprint in the distribution of low redshift galaxies.

[Phys. Rev. Lett. 114, 241301] Published Tue Jun 16, 2015

]]>QCD perturbation theory ignores the compact nature of the $SU(3)$ gauge group that gives rise to the periodic $\theta $ vacuum of the theory. We propose to modify the gluon propagator to reconcile perturbation theory with the anomalous Ward identities for the topological current in the $\theta $ vacuum. As a result, …

[Phys. Rev. Lett. 114, 242001] Published Tue Jun 16, 2015

]]>We introduce a method to achieve the three-dimensional dynamic localization of light. We consider a dynamically modulated resonator lattice that has been previously shown to exhibit an effective gauge potential for photons. When such an effective gauge potential varies sinusoidally in time, dynamic …

[Phys. Rev. Lett. 114, 243901] Published Tue Jun 16, 2015

]]>Inelastic electron tunneling spectroscopy has mapped the phonon density of states in graphene.

[Phys. Rev. Lett. 114, 245502] Published Tue Jun 16, 2015

]]>We employ density functional theory plus dynamical mean field theory and identify the physical origin of why two layers of ${\mathrm{SrVO}}_{3}$ on a ${\mathrm{SrTiO}}_{3}$ substrate are insulating: the thin film geometry lifts the orbital degeneracy, which in turn triggers a first-order Mott-Hubbard transition. Two layers of ${\mathrm{SrVO}}_{\mathrm{\dots}}$

[Phys. Rev. Lett. 114, 246401] Published Tue Jun 16, 2015

]]>We analyze a ${t}_{2g}$ double-exchange system where the orbital directionality of the itinerant degrees of freedom is a key dynamical feature that self-adjusts in response to doping and leads to a phase diagram dominated by two classes of ground states with zigzag and checkerboard patterns. The prevalence…

[Phys. Rev. Lett. 114, 247002] Published Tue Jun 16, 2015

]]>How an electron-hole pair escapes the Coulomb potential at a donor-acceptor interface has been a key issue in organic photovoltaic research. Recent evidence suggests that long-distance charge separation can occur on ultrafast time scales, yet the underlying mechanism remains unclear. Here we use cha…

[Phys. Rev. Lett. 114, 247003] Published Tue Jun 16, 2015

]]>The magnetic behavior of polycrystalline samples of ${\mathrm{Er}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Tb}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ pyrochlores is studied by magnetization measurements and neutron diffraction. Both compounds undergo a magnetic transition at 140 and 130 K, respectively, associated with an ordering of the Ir sublattice, signaled by thermomag…

[Phys. Rev. Lett. 114, 247202] Published Tue Jun 16, 2015

]]>We demonstrate that a ${\mathrm{C}}_{60}$ overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the ${\mathrm{C}}_{60}/\mathrm{Co}$ interfacial magnetic anisotropy that we have measured quantitatively *in situ* as a fun…

[Phys. Rev. Lett. 114, 247203] Published Tue Jun 16, 2015

]]>The giant acceleration (GA) of diffusion is a universal phenomenon predicted by the theoretical analysis given by Reimann *et al.* [Phys. Rev. Lett. **87**, 010602 (2001)]. Here we apply the theory of the GA of diffusion to a single-molecule experiment on a rotary motor protein, ${\mathrm{F}}_{1}$, which is a component o…

[Phys. Rev. Lett. 114, 248101] Published Tue Jun 16, 2015

]]>A new model could help narrow down the source of a disease outbreak.

[Phys. Rev. Lett. 114, 248701] Published Tue Jun 16, 2015

]]>Remarkable advancements in coherence and control fidelity have been achieved in recent years with cryogenic solid-state qubits. Nonetheless, thermalizing such devices to their milliKelvin environments has remained a long-standing fundamental and technical challenge. In this context, we present a sys…

[Phys. Rev. Lett. 114, 240501] Published Mon Jun 15, 2015

]]>Atmospheric ${\mathrm{CO}}_{2}$ concentrations are being closely monitored by remote sensing experiments which rely on knowing line intensities with an uncertainty of 0.5% or better. Most available laboratory measurements have uncertainties much larger than this. We report a joint experimental and theoretical study…

[Phys. Rev. Lett. 114, 243001] Published Mon Jun 15, 2015

]]>We provide a compact full description of multiboson correlation measurements of arbitrary order $N$ in passive linear interferometers with arbitrary input single-photon pure states. This allows us to physically analyze the novel problem of *multiboson correlation sampling* at the output of random linear…

[Phys. Rev. Lett. 114, 243601] Published Mon Jun 15, 2015

]]>