Electron vortex beams carrying intrinsic orbital angular momentum (OAM) are produced in electron microscopes where they are controlled and focused by using magnetic lenses. We observe various rotational phenomena arising from the interaction between the OAM and magnetic lenses. First, the Zeeman coupling, proportional to the OAM and magnetic field strength, produces an OAM-independent Larmor rotation of a mode superposition inside the lens. Second, when passing through the focal plane, the electron beam acquires an additional Gouy phase dependent on the absolute value of the OAM. This brings about the Gouy rotation of the superposition image proportional to the sign of the OAM. A combination of the Larmor and Gouy effects can result in the addition (or subtraction) of rotations, depending on the OAM sign. This behavior is unique to electron vortex beams and has no optical counterpart, as Larmor rotation occurs only for charged particles. Our experimental results are in agreement with recent theoretical predictions.

Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.

Optical diodes controlling the flow of light are of principal significance for optical information processing. They transmit light from an input to an output, but not in the reverse direction. This breaking of time reversal symmetry is conventionally achieved via Faraday or nonlinear effects. For applications in a quantum network, features such as the abilities of all-optical control, on-chip integration, and single-photon operation are important. Here we propose an all-optical optical diode which requires neither magnetic fields nor strong input fields. It is based on a “moving” photonic crystal generated in a three-level electromagnetically induced transparency medium in which the refractive index of a weak probe is modulated by the moving periodic intensity of a strong standing coupling field with two detuned counterpropagating components. Because of the Doppler effect, the frequency range of the crystal’s band gap for the probe copropagating with the moving crystal is shifted from that for the counterpropagating probe. This mechanism is experimentally demonstrated in a room temperature Cs vapor cell.

Topological rigid constraints can be computed rather simply with changing composition and temperature but their estimation remains challenging for other thermodynamic variables. Here, the investigation of densified silicate liquids from molecular dynamics simulations combined with an analysis of radial and angular atomic excursions allows defining a pressure dependence of such constraints. Results show, that for a given composition, the dependence is nonmonotonic as it depends on the interplay between constraints broken by thermal activation and additional constraints arising from the increase of network connectivity under pressure. An anomalous behavior for oxygen bending constraints is obtained in the ($P$, $T$) map which connects to reported anomalies in transport properties and is identified as the pressure analogue of the stress-free Boolchand intermediate phase in rigidity driven by composition.

We propose the local density $\mathrm{\text{approximation}}+\mathrm{\text{Gutzwiller}}$ method incorporating a Green’s function scheme to study the topological physics of correlated materials from the first principles. Applying this method to typical mixed valence materials ${\mathrm{SmB}}_6$, we find its nontrivial $Z_2$ topology, indicating that ${\mathrm{SmB}}_6$ is a strongly correlated topological insulator. The unique feature of this compound is that its surface states contain three Dirac cones in contrast to most known topological insulators.

Phase-resolved transient grating spectroscopy in semiconductor quantum wells has been shown to be a powerful technique for measuring the electron-hole drag resistivity ${\rho }_{eh}$, which depends on the Coulomb interaction between the carriers. In this Letter we develop the interacting drift-diffusion theory, from which ${\rho }_{eh}$ can be determined, given the measured mobility of an electron-hole grating. From this theory we predict a crossover from a high-excitation-density regime, in which the mobility has the “normal” positive value, to a low-density regime, in which Coulomb drag dominates and the mobility becomes negative. At the crossover point, the mobility of the grating vanishes.

A theoretical prediction by de Gennes suggests that the resistance in a $\mathrm{FI}/\mathrm{S}/\mathrm{FI}$ (where FI is a ferromagnetic insulator, and S is a superconductor) structure will depend on the magnetization direction of the two FI layers. We report a magnetotransport measurement in a $\mathrm{EuS}/\mathrm{Al}/\mathrm{EuS}$ structure, showing that an infinite magnetoresistance can be produced by tuning the internal exchange field at the $\mathrm{FI}/\mathrm{S}$ interface. This proximity effect at the interface can be suppressed by an ${\mathrm{Al}}_2{\mathrm{O}}_3$ barrier as thin as 0.3 nm, showing the extreme confinement of the interaction to the interface giving rise to the demonstrated phenomena.

An all-optical experiment long utilized to image phonons excited by ultrashort optical pulses has been applied to a magnetic sample. In addition to circular ripples due to surface acoustic waves, we observe an $X$-shaped pattern formed by propagating spin waves. The emission of spin waves from the optical pulse epicenter in the form of collimated beams is qualitatively reproduced by micromagnetic simulations. We explain the observed pattern in terms of the group velocity distribution of Damon-Eshbach magnetostatic spin waves in the reciprocal space and the wave vector spectrum of the focused ultrafast laser pulse.

Through systematic density functional calculations, the mechanism of the substrate induced spin reorientation transition in $\mathrm{FePc}/\mathrm{O}\mathrm{\text{−}}\mathrm{Cu}(110)$ is explained in terms of charge transfer and rearrangement of Fe-$3d$ orbitals. Moreover, we find giant magnetoelectric effects in this system, manifested by the sensitive dependence of its magnetic moment and magnetic anisotropy energy on an external electric field. In particular, the direction of magnetization of $\mathrm{FePc}/\mathrm{O}\mathrm{\text{−}}\mathrm{Cu}(110)$ is switchable between in-plane and perpendicular axes, simply by applying an external electric field of $0.5\mathrm{eV}/\AA$ along the surface normal.

It has been known for some years that entanglement entropy obtained from partial trace does not provide the correct entanglement measure when applied to systems of identical particles. Several criteria have been proposed that have the drawback of being different according to whether one is dealing with fermions, bosons, or distinguishable particles. In this Letter, we give a precise and mathematically natural answer to this problem. Our approach is based on the use of the more general idea of the restriction of states to subalgebras. It leads to a novel approach to entanglement, which is suitable to be used in general quantum systems and especially in systems of identical particles. This settles some recent controversy regarding entanglement for identical particles. The prospects for applications of our criteria are wide ranging, from spin chains in condensed matter to entropy of black holes.

Various theories beyond the standard model predict new particles with masses in the sub-eV range with very weak couplings to ordinary matter. A parity-odd interaction between polarized nucleons and unpolarized matter proportional to $g_V{g}_A\overrightarrow{s}·\overrightarrow{p}$ is one such possibility, where $\overrightarrow{s}$ and $\overrightarrow{p}$ are the spin and the momentum of the polarized nucleon, and $g_V$ and $g_A$ are the vector and axial vector couplings of an interaction induced by the exchange of a new light vector boson. We report a new experimental upper bound on such possible long-range parity-odd interactions of the neutron with nucleons and electrons from a recent search for parity violation in neutron spin rotation in liquid ${}^4\mathrm{He}$. Our constraint on the product of vector and axial vector couplings of a possible new light vector boson is $g_V{g}_A^n\le {10}^{-32}$ for an interaction range of 1 m. This upper bound is more than 7 orders of magnitude more stringent than the existing laboratory constraints for interaction ranges below 1 m, corresponding to a broad range of vector boson masses above ${10}^{-6}\mathrm{eV}$. More sensitive searches for a $g_V{g}_A^n$ coupling could be performed using neutron spin rotation measurements in heavy nuclei or through analysis of experiments conducted to search for nucleon-nucleon weak interactions and nuclear anapole moments.

We propose to use weak measurements away from the weak-value amplification regime to carry out precision measurements of time delays of light. Our scheme is robust to several sources of noise that are shown to only limit the relative precision of the measurement. Thus, they do not set a limit on the smallest measurable phase shift, contrary to standard interferometry and weak-value-based measurement techniques. Our idea is not restricted to phase-shift measurements and could be used to measure other small effects using a similar protocol.

The one-dimensional Marchenko equation forms the basis for inverse scattering problems in which the scattering object is accessible from one side only. Here we derive a three-dimensional (3D) Marchenko equation which relates the single-sided reflection response of a 3D inhomogeneous medium to a field inside the medium. We show that this equation is solved by a 3D iterative data-driven focusing method, which yields the 3D Green’s function with its virtual source inside the medium. The 3D single-sided Marchenko equation and its iterative solution method form the basis for imaging of 3D strongly scattering inhomogeneous media that are accessible from one side only.

A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at $v\ge 50\mathrm{km}/\mathrm{s}$ by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1–2 axial Alfvén times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement with the minimum energy eigenstate of $\nabla \times \mathit{B}=\lambda \mathit{B}$.

We study the Bose-Einstein condensate phase transition of three-dimensional ultracold bosons with isotropic Rashba spin-orbit coupling. Investigating the structure of Ginzburg-Landau free energy as a function of the condensate density, we show, within the Bogoliubov approximation, that the condensate phase transition is first order with a jump in the condensate density. We calculate the transition temperature and the jump in the condensate density at the transition for large spin-orbit coupling, where the transition temperature depends linearly on the density of particles. Finally, we discuss the feasibility of producing the phase transition experimentally.

Supersurface electron scattering, i.e., electron energy losses and associated deflections in vacuum above the surface of a medium, is shown to contribute significantly to electron spectra. We have obtained experimental verification (in absolute units) of theoretical predictions that the angular distribution of the supersurface backscattering probability exhibits strong oscillations which are anticorrelated with the generalized Ramsauer-Townsend minima in the backscattering probability. We have investigated 500-eV electron backscattering from an Au surface for an incidence angle of 70° and scattering angles between 37° and 165°. After removing the contribution of supersurface scattering from the experimental data, the resulting angular and energy distribution agrees with the Landau-Goudsmit-Saunderson (LGS) theory, which was proposed about 60 years ago, while the raw data are anticorrelated with LGS theory. This result implies that supersurface scattering is an essential phenomenon for quantitative understanding of electron spectra.

We report on robust features of the longitudinal conductivity (${\sigma }_{xx}$) of the graphene zero-energy Landau level in the presence of disorder and varying magnetic fields. By mixing an Anderson disorder potential with a low density of sublattice impurities, the transition from metallic to insulating states is theoretically explored as a function of Landau-level splitting, using highly efficient real-space methods to compute the Kubo conductivities (both ${\sigma }_{xx}$ and Hall ${\sigma }_{xy}$). As long as valley degeneracy is maintained, the obtained critical conductivity ${\sigma }_{xx}\simeq 1.4e^2/h$ is robust upon an increase in disorder (by almost 1 order of magnitude) and magnetic fields ranging from about 2 to 200 T. When the sublattice symmetry is broken, ${\sigma }_{xx}$ eventually vanishes at the Dirac point owing to localization effects, whereas the critical conductivities of pseudospin-split states (dictating the width of a ${\sigma }_{xy}=0$ plateau) change to ${\sigma }_{xx}\simeq e^2/h$, regardless of the splitting strength, superimposed disorder, or magnetic strength. These findings point towards the nondissipative nature of the quantum Hall effect in disordered graphene in the presence of Landau level splitting.

We report high-resolution angle-resolved photoemission studies of epitaxial thin films of the correlated $4d$ transition metal oxide ferromagnet ${\mathrm{SrRuO}}_3$. The Fermi surface in the ferromagnetic state consists of well-defined Landau quasiparticles exhibiting strong coupling to low-energy bosonic modes which contributes to the large effective masses observed by transport and thermodynamic measurements. Upon warming the material through its Curie temperature, we observe a substantial decrease in quasiparticle coherence but negligible changes in the ferromagnetic exchange splitting, suggesting that local moments play an important role in the ferromagnetism in ${\mathrm{SrRuO}}_3$.

A study is presented of the mass and spin-parity of the new boson recently observed at the LHC at a mass near 125 GeV. An integrated luminosity of $17.3{\mathrm{fb}}^{-1}$, collected by the CMS experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, is used. The measured mass in the $ZZ$ channel, where both $Z$ bosons decay to $e$ or $\mu$ pairs, is $126.2\pm 0.6(\mathrm{stat})\pm 0.2(\mathrm{syst})\mathrm{GeV}$. The angular distributions of the lepton pairs in this channel are sensitive to the spin-parity of the boson. Under the assumption of spin 0, the present data are consistent with the pure scalar hypothesis, while disfavoring the pure pseudoscalar hypothesis.

We investigate two flavor quantum chromodynamics (QCD) in the presence of $CP$-odd electromagnetic background fields and determine, by means of lattice QCD simulations, the induced effective $\theta$ term to first order in $\overrightarrow{E}·\overrightarrow{B}$. We employ a rooted staggered discretization and study lattice spacings down to 0.1 fm and Goldstone pion masses around 480 MeV. In order to deal with a positive measure, we consider purely imaginary electric fields and real magnetic fields, and then exploit the analytic continuation. Our results are relevant to a description of the effective pseudoscalar quantum electrodynamics—QCD interactions.