Influence of Geometry on Topological Insulator Behavior of Bi(2)Te(3) Nanowires

  • Authors:
    Parijat Sengupta (Purdue), Tillmann C. Kubis (Purdue), Yaohua Tan (Purdue), Mykhailo Povolotskyi (Purdue), Gerhard Klimeck (Purdue)
    Publication ID:
    Publication Type:
    Received Date:
    Last Edit Date:
    1806.005 (University of Notre Dame)


Bi(2)Te(3) and Bi(2)Se(3) are well known 3D-topological insulators. Thin films made of these materials exhibit metal-like surface states with a Dirac dispersion. In this work the influence of thickness of the thin-film on the surface-state dispersion is investigated. At low film thickness, the surface states couple to each other and a band gap is opened. Dispersion of these states is also impacted by growth conditions, particularly the substrate. Asymmetric growth conditions are simulated and a Rashba-type splitting of the Dirac cones is observed in agreement with experiment. Low film thickness and asymmetric growth conditions together lead to formation of displaced hyperbolas. The Fermi-velocity of the surface states and band-gap are computed as a function of the film thickness. The surface states are spin-polarized with no out-of-plane component and locked perpendicular to the momentum vector. A spin-filter is proposed based on this principle by utilizing two 3-D topological insulators placed together.

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