The discovery of the quantum Hall (QH) effect led to the realization of a topological electronic state with dissipationless currents circulating in one direction along the edge of a two dimensional electron layer under a strong magnetic field. 1,2 The quantum anomalous Hall (QAH) effect shares a similar physical phenomenon as the QH effect, whereas its physical origin relies on the intrinsic spin-orbit coupling and ferromagnetism.

The fundamental challenge for designing transparent conductors used in photovoltaics, displays and solid-state lighting is the ideal combination of high optical transparency and high electrical conductivity. Satisfying these competing demands is commonly achieved by increasing carrier concentration in a wide-bandgap semiconductor with low effective carrier mass through heavy doping, as in the case of tin-doped indium oxide (ITO). Here, an alternative design strategy for identifying high-conductivity, high-transparency metals is proposed, which relies on strong electron-electron interactions resulting in an enhancement in the carrier effective mass. This approach is experimentally verified using the correlated metals SrVO3 and CaVO3, which, despite their high carrier concentration (>2.2 × 10(22) cm(-3)), have low screened plasma energies (<1.33 eV), and demonstrate excellent performance when benchmarked against ITO. A method is outlined to rapidly identify other candidates among correlated metals, and strategies are proposed to further enhance their performance, thereby opening up new avenues to develop transparent conductors.

We report dielectric constant measurements showing critical fluctuation-induced thinning of 4 He films near the superfluid transition. The films are adsorbed on a stack of copper electrodes suspended at different heights above bulk liquid. We calibrate the measurements by assuming that the film thickness away from the transition region at different heights is accurately given by theory. The thinning is found to be consistent with finite-size scaling, if the value of the scaling function for each thickness is normalized by its value at the minimum.

Metallic nanowires (Au, Ag, Cu, Ni, Co, and Rh) with an average diameter of 40 nm and a length of 3-5 μm have been fabricated by electrodeposition in the pores of track-etched polycarbonate membranes. Structural characterizations by transmission electron microscopy (TEM) and electron diffraction showed that nanowires of Au, Ag, and Cu are single-crystalline with a preferred [111] orientation, whereas Ni, Co, and Rh wires are polycrystalline. Possible mechanisms responsible for nucleation and growth for single-crystal noble metals versus polycrystalline group VIII-B metals are discussed.

The influence of quenched disorder on the critical behavior of superfluid He is studied by confinement of the helium to the pores of three diflerent porous media: Vycor, xerogel, and aerogel glasses. In each case a well defined power-law behavior for the superfluid density is observed as the transition temperature is approached. In Vycor the superfluid critical exponent is bulklike, whereas strikingly diff'erent critical exponents are seen in the other two media.

We consider in our work single crystal thin films of Bi2Se3, grown by molecular beam epitaxy, both with and without Pb doping. Angle-resolved photoemission data demonstrate topological surface states with a Fermi level lying inside the bulk band gap in the Pb doped films. Transport data show weak localization behavior, as expected for a thin film in the two-dimensional limit (when the thickness is smaller than the inelastic mean free path), but a detailed analysis within the standard theoretical framework of diffusive transport shows that the temperature and magnetic field dependences of resistance cannot be reconciled in a theory that neglects inter-electron interactions. We demonstrate that an excellent account of quantum corrections to conductivity is achieved when both disorder and interaction are taken into account. These results clearly demonstrate that it is crucial to include electron electron interaction for a comprehensive understanding of diffusive transport in topological insulators. While both the ordinary bulk and the topological surface states presumably participate in transport, our analysis does not allow a clear separation of the two contributions.

We present new capacitance measurements of critical Casimir force-induced thinning of 4He films near the superfluid transition, focused on the region below Tlambda where the effect is the greatest. 4He films of 238, 285, and 340 A thickness are adsorbed on atomically smooth, N-doped silicon substrates. The Casimir force scaling function theta, deduced from the thinning of these three films, collapses onto a single universal curve, attaining a minimum theta=-1.30+/-0.03 at x=td1/nu=-9.7+/-0.8 A1/nu. The collapse confirms the finite-size scaling origin of the dip in the film thickness. Separately, we also confirm the presence down to 2.13 K of the Goldstone or surface fluctuation force, which makes the superfluid film approximately 2 A thinner than the normal film.

We have measured the pressure dependence of the supersolid fraction by a torsional oscillator technique. Superflow is found from 25.6 bar up to 136.9 bar. The supersolid fraction in the low temperature limit increases from 0.6 % at 25.6 bar near the melting boundary up to a maximum of 1.5% near 55 bar before showing a monotonic decrease with pressure extrapolating to zero near 170 bar.