Energy-Gap Opening Near the Dirac Point after the Deposition of Cobalt on the (0001) Surface of the Topological Insulato
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INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 10–13, 2020
Energy-Gap Opening Near the Dirac Point after the Deposition of Cobalt on the (0001) Surface of the Topological Insulator BiSbTeSe2 A. K. Kaveeva,*, A. G. Banshchikova, A. N. Terpitskiya, V. A. Golyashovb, O. E. Tereshchenkob, K. A. Kokhc, D. A. Estyunind, and A. M. Shikind a Ioffe
Institute, St. Petersburg, 194021 Russia Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia c Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia d St.Petersburg State University, St. Petersburg, 199034 Russia *e-mail: [email protected] b
Received April 15, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—It is shown for the first time that Co subnanometer coatings deposited by molecular-beam epitaxy on the (0001) surface of the topological insulator BiSbTeSe2 at a temperature of 330°C open an energy gap in the spectrum of topological surface states in the region of the Dirac point with a shift of the Dirac-point position caused by the preliminary deposition of an adsorbate at room temperature. The gap width is 21 ± 6 meV. Temperature-dependent measurements in the range of 15–150 K show no changes in the energy-gap width. Keywords: topological insulators, spintronics, energy gap at the Dirac point, doping DOI: 10.1134/S1063782620090146
1. INTRODUCTION At present, topological insulators (TIs) are attracting strong scientific interest in solid-state physics and semiconductor physics. The surface states of these materials have exotic properties and are topologically protected by time-reversal symmetry [1, 2]. These materials have a unique electronic and spin structure consisting in the presence of a band gap in the material bulk and the Dirac cone of spin-polarized conducting surface states formed due to strong spin-orbit interaction. The deposition of ultrathin ferromagnetic (FM) coatings on the surface of a TI is attractive from the viewpoint of controlling the conductive properties of the surface states: it is possible to remove topological protection due to the proximity effect, which consists in the influence of the magnetic moment of a ferromagnet on the spin-polarized surface states of a TI [3]. This elimination of the time inversion should lead to removal of the topological security and the opening of an energy gap in the region of the Dirac point. The inverse effect consists in the possible influence of the current in spin-polarized states on the magnetic moment of the ferromagnetic coating [4, 5]. From the viewpoint of the mentioned application of FM/TI epitaxial systems, it is important to study changes in the electronic, structural, and interfacial properties of TI
during the deposition of ferromagnetic material. There are several studies related to experimental investigations of the contact between FM and TI in various systems, for example, using Bi2Se3 [6] or Sb2Te3 [7, 8] as the TI.
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