"Hall effects, Spin Orbit Coupling, and Spin Orbit Torque in Topological Insulators" by Kang Wang (UCLA)

Thursday, May 21, 2015 - 4:00pm to 5:00pm
Physics and Astronomy Colloquium

Thursdays, 4:00-5:00 pm

1-434 Physics and Astronomy (map)
Reception from 3:30-4:00 p.m.
(unless otherwise posted)

Guest Speaker: Kang L. Wang (University of California, Los Angeles)

Talk Title:  “Hall effects, Spin Orbit Coupling, and Spin Orbit Torque in Topological Insulators”


The Hall effect discovered more than 130 years ago has found ubiquitous applications in today automobiles.  Recent interests in spin Hall due to large spin orbit interaction have led to many advances for improving energy efficiency in the stride to meeting the critical challenge of increasing energy dissipation.   

The presence of large SOC can render an insulator to a topological insulator exhibiting Dirac electron surface states.  When magnetic order is introduced into topological insulators (TIs), the time-reversal-symmetry (TRS) is broken, and the non-trivial topological surface is driven into a new massive Dirac-fermions state. By controlling the magnetic (Cr) doping concentration and the Fermi level position, we show that the quantum anomalous Hall effect (QAHE) in the macroscopic millimeter-size magnetic-doped TI Cr-doped ((BixSb1-x)2Te3) films. Furthermore, we find that the stability of the dissipationless chiral edge conductance is well-maintained as the film thickness varies across the 2D hybridization limit.

TI/Cr-doped TI heterostructures can also be used for the electrical manipulation of magnetization switching via giant spin–orbit torque (SOT).  We demonstrate that the SOT required for magnetization switching in such magnetic TI-based bilayer structures is three orders of magnitude more efficient than that of heavy metals.  All these exotic magnetic TI-based phenomena will serve as fundamental steps to further explore the TRS-breaking TI systems.


For more information, contact Karoly Holczer

1-434 PAB