You are here: Home / Seminars / Seminar Database / Special Seminar: Exploring quantum anomalous Hall effect in magnetically doped topological insulator films*

Special Seminar: Exploring quantum anomalous Hall effect in magnetically doped topological insulator films*

Main Content

Cui Zu Chang, Francis Bitter Magnet Lab, MIT
When
24 January 2014 from 1:00 PM to 2:00 PM
Where
339 Davey Laboratory
Contact Name
Contact Phone
814-863-2622
Add event to calendar
vCal
iCal

In this talk, I will review electronic structure, electronic and magnetic properties of thin films of various TIs in particular the Cr doped Bi2Se3 family (including Bi2Se3, Bi2Te3, Sb2Te3, (BixSb1-x)2Te3 and Bi2(SexTe1-x)3), Our systematic investigation of film growth (by MBE) and characterization by in-situ STM and ARPES, and ex-situ magneto-resistance measurements will be discussed. In one of the better studied TIs, Cr-doped Bi2Se3, no long range ferromagnetic order was observed. Our analysis suggested that the absence of long-range ferromagnetic order is due segregation of Cr dopants at low doping level and possibly very weak spin-orbit coupling at high Cr doping level so that band inversion cannot occur preventing the van Vleck mechanism to take place. On the other hand, long range ferromagnetic order was found in Cr-doped Te-based TIs (Bi2Te3, Sb2Te3, (BixSb1-x)2Te3), which was insensitive to the carrier type and density. Finally in thin films of Cr doped (BixSb1-x)2Te3 topological insulator, quantum anomalous Hall (QAH) effect was observed : in the remnant state (without a magnetic field) the Hall resistance was found to be exactly quantized at h/e2 as expected(~25.8kW) accompanied by a significant drop of the longitudinal resistance. The longitudinal resistance vanishes under a strong magnetic field whereas the Hall resistance remains at the quantized value.

*Work carried out at Tsinghua University, as part of the PhD thesis.

Seminars