We propose an experimental scheme to observe spin-orbit coupling effects of a two-dimensional (2D) Fermi atomic gas cloud by coupling its internal electronic states (pseudospins) to radiation in a Lambda configuration. The induced spin-orbit (SO) coupling can be of the Dresselhaus and Rashba type with and without a Zeeman term. We show that the optically induced SO coupling can lead to a spin-dependent effective mass under appropriate condition, with one of them able to be tuned between positive and negative effective masses. As a direct observable we show that in the expansion dynamics of the atomic cloud the initial atomic cloud splits into two clouds for the positive effective mass case regime, and into four clouds for the negative effective mass regime. [3,4]. In correspondence to the spin of an electron, the internal degree of freedom of an atom (pseudospin) is represented by the superposition of its electronic states (hyperfine levels). SO coupling can be equivalently depicted as the interaction between an effective non-Abelian gauge potential and a particle with (pseudo)spin. In quantum systems, the idea generating a gauge field adiabatically was proposed by Wilczek and Zee more than twenty years ago [5]. Recently, such an idea was applied to atomic systems, where the motion of atoms in a position dependent laser configuration gives rise to an effective non-Abelian gauge potential [6,7,8,9,10], which can lead to an effective SO interaction in an ultracold atomic gas [11,12,13].Realization of SO interaction in atomic gases opens new possibility of studying spintronic effects, e.g. spin relaxation [11], Zitterbewegung [12] and SHE, in atomic systems which provide an extremely clean environment, allowing in a controllable fashion unique access to the study of complex physics. However, experimental detection of such SO effects in atoms requires to measure the pseudospins (not just hyperfine levels) that are usually not directly observable for atomic systems. In this letter, we propose an experimental scheme to study SO coupling effects, based on a trapped two-dimensional (2D) Fermi atomic gas with a simple internal three-level Λ-type setup. We demonstrate that an effective SO interaction, e.g. Rashba and linear Dresselhaus terms, can be obtained by coupling atoms with a three-level configuration to spatially varying laser fields. The optically induced SO coupling can lead to a spin-dependent effective masses under proper condition. A direct observable of this effects is in the expansion dynamics for each of the effective mass cases after the external trap is switched off and we predict that the initial atomic cloud splits into two or four clouds.|c>(1/2)Ω We consider a cloud of quasi 2D (y-z plane) Fermi atomic gas with internal three-level Λ-type configuration (see Fig. 1 (a)) coupled to radiation. The transition |b → |a is coupled by the laser field with Rabi-frequency Ω 1 = Ω 10 exp[iφ 1 (r)] and the transition |c → |a is coupled by another laser field Ω 2 = Ω 20 exp[iφ 2 (r)], where φ 1,2 (r) are positi...

The anomalous Hall effect in a magnetic two-dimensional electron gas with Rashba spin-orbit coupling is studied within the Kubo-Streda formalism in the presence of pointlike potential impurities. We find that all contributions to the anomalous Hall conductivity vanish to leading order in disorder strength when both chiral subbands are occupied. In the situation that only the majority subband is occupied, all terms are finite in the weak scattering limit and the total anomalous Hall conductivity is dominated by skew scattering. We compare our results to previous treatments and resolve some of the discrepancies present in the literature.

Black phosphorus is a monatomic semiconducting layered material that degrades exothermically in the presence of light and ambient contaminants. Its degradation dynamics remain largely unknown. Even before degradation, local-probe studies indicate non-negligible local curvature—through a nonconstant height distribution—due to the unavoidable presence of intrinsic defects. We establish that these intrinsic defects are photo-oxidation sites because they lower the chemisorption barrier of ideal black phosphorus (>10 eV and out of visible-range light excitations) right into the visible and ultraviolet range (1.6 to 6.8 eV), thus enabling photoinduced oxidation and dissociation of oxygen dimers. A full characterization of the material’s shape and of its electronic properties at the early stages of the oxidation process is presented as well. This study thus provides fundamental insights into the degradation dynamics of this novel layered material.

Abstract. Graphene provides a fascinating testbed for new physics and exciting opportunities for future applications based on quantum phenomena. To understand the coherent flow of electrons through a graphene device, we employ a nanoscale probe that can access the relevant length scales -the tip of a liquid-He-cooled scanning probe microscope (SPM) capacitively couples to the graphene device below, creating a movable scatterer for electron waves. At sufficiently low temperatures and small size scales, the diffusive transport of electrons through graphene becomes coherent, leading to universal conductance fluctuations (UCF). By scanning the tip over a device, we map these conductance fluctuations vs. scatterer position. We find that the conductance is highly sensitive to the tip position, producing δG ∼ e 2 /h fluctuations when the tip is displaced by a distance comparable to half the Fermi wavelength. These measurements are in good agreement with detailed quantum simulations of the imaging experiment, and demonstrate the value of a cooled SPM for probing coherent transport in graphene.

Raman scattering plays a key role in unraveling the quantum dynamics of graphene, perhaps the most promising material of recent times. It is crucial to correctly interpret the meaning of the spectra. It is therefore very surprising that the widely accepted understanding of Raman scattering, i.e., Kramers-Heisenberg-Dirac theory, has never been applied to graphene. Doing so here, a remarkable mechanism we term"transition sliding" is uncovered, explaining the uncommon brightness of overtones in graphene. Graphene's dispersive and fixed Raman bands, missing bands, defect density and laser frequency dependence of band intensities, widths of overtone bands, Stokes, anti-Stokes anomalies, and other known properties emerge simply and directly.