Seminars

  • Understanding Magnetic Ordering Mechanism and Electronic Structure of the Quantum Anomalous Hall Effect in Magnetically Doped Topological Insulators

  • Speaker : Dr. Jeongwoo Kim
    Affiliation : Department of Physics and Astronomy, University of California
    Date : November 30, 2017 4:00 PM
    Place : Building 110 | Room 510
    Contact : noejung@unist.ac.kr; hsjin@unist.ac.kr
    Host : Noejung Park & Hosub Jin
  • Abstract

  • Realization of transverse electric currents without external magnetic fields, so called the quantum anomalous Hall effect (QAHE), is achieved in Cr-doped topological insulating (Bi,Sb)2Te3 compounds. However, detailed mechanism of QAHE and magnetic ordering in topological insulators (TIs) is still unclear with several models in controversy. We investigate magnetic ordering and the QAHE in Cr-doped TIs using systematic first-principles calculations, explaining the mechanism responsible for ferromagnetic order and the reason why Sb2Te3 is a better QAHE host than Bi2Se3 or Bi2Te3. We demonstrate that these magnetic topological insulators have relatively long-range exchange interactions within quintuple layers, and weak interactions between quintuple layers. Our analyses for the spin splitting of the topological surface states and the calculated Hall conductivity suggest that the temperature at which the QAHE occurs in these materials can be significantly enhanced by Mo-Cr co-doping. Our findings deepen the understanding of magnetic ordering and topological features of magnetic TIs.