Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS Prairie Section
Volume 58, Number 15
Thursday–Saturday, November 7–9, 2013; Columbia, Missouri
Session E2: Condensed Matter Physics III |
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Chair: Sashi Satpathy, University of Missouri Room: Memorial Union Stotler I&II |
Friday, November 8, 2013 4:00PM - 4:36PM |
E2.00001: Superconductivity in Topological Insulators Invited Speaker: Yew San Hor Topological phases of matter such as three-dimensional topological insulators have been discovered and found to exhibit fascinating quantum phenomena. These materials have shown robust quantized properties i.e. bulk insulating phase but surface conducting phase with Dirac excitations. Three-dimensional topological superconductors have been theoretically proposed recently. These hypothetical topological superconductors (TSCs) are predicted to possess itinerant massless Majorana fermions which are charge neutral and spin 1/2 quasiparticles that only emerge and propagate on the surface. The Bogoliubov-de Gennes (BdG) Hamiltonian for the quasiparticles of a TSC is analogous to the Hamiltonian of a TI, with the superconducting gap corresponding to the band insulating gap. However, TSCs and the associated Majorana quasiparticles have not been conclusively established in real materials so far. Hence, this presentation will show by chemical doping, a TI can change into a bulk superconductor which could be a TSC. The first example i.e. Cu$_{\mathrm{x}}$Bi$_{2}$Se$_{3}$ was discovered few years ago to be a promising TSC. Several other promising candidates of TSCs will also be shown. [Preview Abstract] |
Friday, November 8, 2013 4:36PM - 4:48PM |
E2.00002: The lifetime of Dirac plasmons in graphene Alessandro Principi, Giovanni Vignale, Matteo Carrega, Marco Polini Dirac plasmons in a doped graphene sheet have recently been shown to enable confinement of light to ultrasmall volumes. In this work we calculate the intrinsic lifetime of a Dirac plasmon in a doped graphene sheet by analyzing the role of electron-electron interactions beyond the random phase approximation. The damping mechanism at work is intrinsic since it operates also in disorder-free samples and in the absence of lattice vibrations. We demonstrate that graphene's sublattice-pseudospin degree of freedom suppresses intrinsic plasmon losses with respect to those that occur in ordinary two-dimensional electron liquids. We relate our findings to a microscopic calculation of the homogeneous dynamical conductivity at energies below the single-particle absorption threshold. Finally, we compute the impact of disorder on Dirac plasmon losses and then show that a very reasonable concentration of charged impurities yields a plasmon damping rate which is in good agreement with s-SNOM experimental results. [Preview Abstract] |
Friday, November 8, 2013 4:48PM - 5:00PM |
E2.00003: Density-Functional Theory of Thermoelectric Phenomena Florian G. Eich, Giovanni Vignale, Massimiliano Di Ventra Thermoelectric phenomena play an important role in the development of sustainable energy sources. We have introduced a non-equilibrium density-functional theory of local temperature and associated energy density that is particularly suited for the study of thermoelectric phenomena from first principles [1]. This theory rests on a local temperature field coupled to the energy-density operator. We identify the excess energy density, in addition to the charge density, as fundamental variable. These densities are obtained from an effective non-interacting Kohn-Sham system. We show that the Schr{\"o}dinger equation for the Kohn-Sham system features a spatially varying mass representing the effect of local temperature variations. Furthermore we discuss strategies to approximate the Kohn-Sham potential and the spatially varying mass emerging in the Kohn-Sham equation. \\[4pt] [1] arXiv:1308.2311 [Preview Abstract] |
Friday, November 8, 2013 5:00PM - 5:36PM |
E2.00004: Magnetism in iron-based high-temperature superconductors and its effect on lattice and superconductivity Invited Speaker: Andreas Kreyssig Shortly after the discovery of iron-based high-temperature superconductors in 2008, extensive studies using neutron and x-ray scattering techniques have revealed a strong interconnection of magnetism, lattice and superconductivity. In this presentation I will give an overview of the complex interplay between these phenomena and will bring it into context with other unusual superconductors. I will illustrate the phase relations exemplarily on the family of $A$Fe$_2$As$_2$-based material ($A$ = Ba, Sr, Ca) where a stripe-like antiferromagnetic order is coupled to a lattice distortion implying a strong coupling between magnetism and structure. Partial chemical element substitution suppresses these transitions and superconductivity occurs. \\[4pt] The study was performed in collaboration with M. G. Kim$^{*}$, G. S. Tucker$^{*}$, D. K. Pratt$^{*}$, S. Nandi$^{*}$, W. Tian$^{\#}$, J. Zarestky$^{*}$, J.-W. Kim$^+$, G. E. Granroth$^{*}$, K. Marty$^{\#}$, M. D. Lumsden$^{\#}$, T. Heitmann$^{=}$, A. Thaler$^{*}$, N. Ni$^{*}$, S. L. Bud'ko$^{*}$, P. C. Canfield$^{*}$, R. M. Fernandes$^{*}$, J. Schmalian$^{*}$, R. J. McQueeney$^{*}$, and A. I. Goldman$^{*}$; $^{*}$Ames Laboratory, and Iowa State University; $^+$APS, Argonne; $^{\#}$HFIR, Oak Ridge; $^{=}$MURR, University of Missouri. [Preview Abstract] |
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