Bulletin of the American Physical Society
2019 Annual Meeting of the APS Far West Section
Volume 64, Number 17
Friday–Saturday, November 1–2, 2019; Stanford, California
Session H01: Condensed Matter |
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Chair: Andreas Bill, California State University, Long Beach Room: Science Teaching and Learning Center STLC 114 |
Saturday, November 2, 2019 3:30PM - 3:42PM |
H01.00001: The harmonic metric for hierarchic quasiperiodics Antony Bourdillon Sharp diffraction patterns show long range order [1] in i-Al6Mn; translational symmetry is found—by phase contrast, optimum-defocus imaging—to be hierarchic. The icosahedral diffraction pattern was novel in two ways: it included five-fold symmetric axes; having moreover diffraction orders in geometric series, imprecisely called Fibonacci. These orders differ from Bragg diffraction which is linear. How does an X-ray sine wave, or electron beam, scatter off the hierarchic structure? Like quantum mechanics, the scattering depends on harmonics: quasi-Bragg angles are derived from quasi-structure factors with a metric that is derived numerically and analytically. All atoms scatter: the metric harmonizes the incident sine wave with hierarchic translational symmetry. The ratio (1.5/tau) 2 produces the harmonic metric, together with geometric series diffraction from a consistent structure [2]. [1] Shechtman, D, et al. (1984) Phys. Rev. Lett. 53, 1951, http://dx.doi.org/10.1103/PhysRevLett.53.1951 [2] Bourdillon, AJ, J. Mod. Phys. 10 [6] 624 (2019), DOI: 10.4263/jmp.2019.106044 [Preview Abstract] |
Saturday, November 2, 2019 3:42PM - 3:54PM |
H01.00002: MgO$^{\mathrm{.}}$Fe$_{\mathrm{E-6}}$ and NbO$^{\mathrm{.}}$Fe$_{\mathrm{E-2}}$ 2D XRD Galileo-Gor'kov conductance Juana V Acrivos, Angelica Alvarado, Sara Catherine Weaver Warner, Jeffery Kmiek, Lei Chen We investigate doped materials electronic processes, structure, and magnetic properties. Magnetic resonance esr indicates (Fe,Mn)$_{\mathrm{E-6}}$MgO, Fe$_{\mathrm{\% }}$NbO stability is by vacancy $\emptyset $ polarized free electrons e$^{\mathrm{-}}_{\mathrm{P}}$. We describe stability by two energy X-Ray diffraction 2D XRD, SLAC:SSRL BL2.1 Si(111) crystal detected resonance enhanced scans: E$\to $Fe-Mn K-edges, and E$+\Delta $E obtain Bragg: I(E)$_{\mathrm{\nu =0,1,}}$ vs. Q,Q*\underline {\textless }60/nm, sideband structure $\nu $q$_{\mathrm{PLD}}$ (q$_{\mathrm{PLD}}$\textless 0.1/nm) and followed by exited states relaxation coherent stimulated absorption/emission, Compton: I*(E)Q aligned vs. $\Delta $E$+$E,\textbf{p}*$=$Q*-Q. Element \textbf{\textit{e}} bonds are described by binding state Tables \textbf{\textit{e}}($\varepsilon $:nlj) $=\Delta $E\textpm 5eV,\textbf{p}* $=$Fe;O;Mg;Nb(K,L,M states). The quasi particle, qsp Galileo conductance \underline {c}$_{\mathrm{cr\thinspace }}=\hbar $q$_{\mathrm{PLD}}$/m$_{\mathrm{e}}$*, periodic lattice distortion, associated with esr spin-lattice interaction 3a $=$7$\mu $eV, is compared to similar vacancy structures: graphite C(gr$_{\mathrm{a,c}})$, magnetite M,$_{\mathrm{\thinspace }}$Prussian$_{\mathrm{\thinspace }}$Blue PB, and superconductor SC T$_{\mathrm{c}}$\textasciitilde 200K oxide, Bi$_{\mathrm{1-x}}$Pb$_{\mathrm{x=0.3}}$:Sr:Ca:Cu::2:2:n-1:n\underline {\textless }30: Room T results indicate \underline {c}$_{\mathrm{cr}}$(C(gr$_{\mathrm{c,a}}))$ $=$\textbraceleft 40,E3\textbraceright nm/ps \textgreater \underline {c}$_{\mathrm{cr}}$(Fe$_{\mathrm{\% }}$NbO) \textasciitilde 10nm/ps \textgreater \underline {c}$_{\mathrm{cr}}$(M) \textgreater c$_{\mathrm{cr}}$(\textbf{\textit{e}}$_{\mathrm{E-6}}$MgO) \textasciitilde \underline {c}$_{\mathrm{cr}}$(PB) \textasciitilde c$_{\mathrm{cr}}$(SC) \textasciitilde nm/ps, is achieved through vacancy $\emptyset $ by Pauling ligand strength order: CC\textgreater CN$^{\mathrm{-}}$\textgreater O$^{\mathrm{=}}$\textgreater OH$_{\mathrm{2}}$ below the atomic limit \underline {c}$_{\mathrm{cr0\thinspace }}=$e$^{\mathrm{2}}$/$\hbar $ $=$2.18nm/fs. [Preview Abstract] |
Saturday, November 2, 2019 3:54PM - 4:06PM |
H01.00003: Observation of long carrier lifetime in photoexcited Sb-doped Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ nanoplates Adam Gross, Yasen Hou, Antonio Rossi, Dong Yu, Inna Vishik Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ is a three-dimensional topological insulator (TI), characterized by a bulk band gap of approximately 0.3 eV and a Dirac-like protected surface state.~The material is usually n-type due to selenium vacancies, and chemical substitution, such as Sb-doping, is typically needed to bring the chemical potential into the bulk band gap.~We will present ultrafast transient reflectivity measurements on Bi$_{\mathrm{2}}$Se$_{\mathrm{3}}$ and (Bi,Sb)$_{\mathrm{2}}$Se$_{\mathrm{3}}$ nanoplates which reveal starkly different carrier dynamics in n-type vs. insulating samples.~This will be discussed in the context of optoelectronic applications of TIs, including as a material for exciton condensation. [Preview Abstract] |
Saturday, November 2, 2019 4:06PM - 4:18PM |
H01.00004: Electrostatic Tuning of the Coulomb Interaction in Single-Layer Graphene Nicholas Dale, Claudia Fatuzzo, Ryo Mori, Iqbal Bakti Utama, Jonathan Denlinger, Conrad Stansbury, Sihan Zhao, Kyunghoon Lee, Takashi Taniguchi, Kenji Watanabe, Feng Wang, Alessandra Lanzara The Landau-Fermi Liquid Theory maps an interacting liquid of electrons to a non-interacting gas of quasiparticles. This picture breaks down in Graphene, because the bare Coulomb interaction is preserved near the charge neutrality point. In this talk, I will discuss recent in-operando angle-resolved photoemission studies on single layer graphene where we directly visualize modifications of its electronic band structure upon tuning the Fermi Energy. [Preview Abstract] |
Saturday, November 2, 2019 4:18PM - 4:30PM |
H01.00005: Tuning the Electronic Band Structure of Copper Selenide Cu2Se Thin Films Grown via Molecular Beam Epitaxy Ryan Van Haren, Toyanath Joshi, David Lederman Copper chalcogenides, compounds consisting of copper and one or more of the chalcogen family of elements S, Se, and Te, have recently become of interest to materials scientists for their unique electronic band structures and predicted electronic topological behavior. Of particular interest among this class of materials is the copper selenide Cu2Se. This material has long been known to be an excellent thermoelectric material and has recently garnered interest for its electronic band structure that is tunable by introducing copper vacancies into the crystal structure. In this work, we will present our successful growths of high quality, single phase, copper deficient Cu2Se thin films in the (200) orientation via molecular beam epitaxy. Using reflection high energy electron diffraction (RHEED) and x-ray diffraction (XRD) measurements, we will show how we are able to quantify the copper concentration by analyzing the subtle shifts in our observed XRD spectra corresponding to small changes in the lattice spacing due to these copper vacancies. In this manner we will demonstrate how we are able to tune the copper vacancies and electronic band structure by precise control of the crystal's growth parameters. [Preview Abstract] |
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