The effects of k-dependent self-energy in the electronic structure of correlated materials

It is known from self-energy calculations in the electron gas and sp materials based on the GW approximation that a typical quasiparticle renormalization factor (Z factor) is approximately 0.7-0.8. Band narrowing in electron gas at rs = 4 due to correlation effects, however, is only approximately 10%, significantly smaller than the Z factor would suggest. The band narrowing is determined by the frequency-dependent self-energy, giving the Z factor, and the momentum-dependent or nonlocal self-energy. The results for the electron gas point to a strong cancellation between the effects of frequency- and momentum-dependent self-energy. It is often assumed that for systems with a nar- row band the self-energy is local. In this work we show that even for narrow-band materials, such as SrVO3, the nonlocal self-energy is important.Comment: 7 pages, 6 figure

Dijet Cross Section and Longitudinal Double Spin Asymmetry Measurements in Polarized Proton-proton Collisions at \sqrt{s}=200 GeV at STAR

These proceedings show the preliminary results of the dijet cross sections and the dijet longitudinal double spin asymmetries A_LL in polarized proton-proton collisions at \sqrt{s} = 200 GeV at the mid-rapidity |eta| < 0.8. The integrated luminosity of 5.39 pb^{-1} collected during RHIC Run-6 was used in the measurements. The preliminary results are presented as functions of the dijet invariant mass M_jj. The dijet cross sections are in agreement with next-to-leading-order pQCD predictions. The A_LL is compared with theoretical predictions based on various parameterizations of polarized parton distributions of the proton. Projected precision of data analyzed to date from Run-9 are shown.Comment: 8 pages, 5 figures, Proceedings of the SPIN2010 conference (Juelich, Germany, 2010

Size dependent line broadening in the emission spectra of single GaAs quantum dots: Impact of surface charges on spectral diffusion

Making use of droplet epitaxy, we systematically controlled the height of self-assembled GaAs quantum dots by more than one order of magnitude. The photoluminescence spectra of single quantum dots revealed the strong dependence of the spectral linewidth on the dot height. Tall dots with a height of ~30 nm showed broad spectral peaks with an average width as large as ~5 meV, but shallow dots with a height of ~2 nm showed resolution-limited spectral lines (<120 micro eV). The measured height dependence of the linewidths is in good agreement with Stark coefficients calculated for the experimental shape variation. We attribute the microscopic source of fluctuating electric fields to the random motion of surface charges at the vacuum-semiconductor interface. Our results offer guidelines for creating frequency-locked photon sources, which will serve as key devices for long-distance quantum key distribution.Comment: 6 pages, 6 figures; updated figs and their description

Conductivity and Structure of Superionic Composite (AgI)0.6(NaPO3)0.4

Superionic conductors are of considerable interest from both application and fundamental points of view. Superionic solid electrolytes can be used for batteries, fuel cells and sensors. We have used melt quenching to make a new superionic composite (AgI)0.6(NaPO3)0.4 which exhibits an ionic conductivity of about 2 x 10-4 S/cm at ambient temperature. The conductivity of crystalline AgI and NaPO3 glass are lower of orders of magnitude. (AgI)0.6(NaPO3)0.4 is a composite material containing both crystalline and glass phases. The paper presents the conductivity as a function of temperature measured by impedance spectroscopy and the crystal structure performed by a high resolution powder diffractometer, VEGA at the Neutron Science Laboratory (KENS), KEK, Japan