Department of Physics, NCU
Magnetic Topological Insulators
Speaker
Dr. Peng-Jen Chen陳鵬仁
Institute of Physics, Academia Sinica
Date 2018.04.18 (Wed)
Time 13:00-15:00
Place S4-625
Abstract: The topological insulators (TIs) are emerging quantum matters that exhibit intriguing properties on surfaces. It is well-known that the nontrivial topology, characterized by Z2 invariant, is protected by the time-reversal symmetry (TRS). That is to say, breaking of the TRS simultanesouly suppresses the nontrivia topology. However, materials with specific antiferromagnetic configuration can still be Z2 nontrivial due to the presence of a new protecting symmetry. In this talk, I will demonstrate that SmB6 is possibly a candidate for this antiferromagnetic topological phase. This is the first candidate that has been found to exhibit such topological phase since the proposal of the theory in 2010.
Another interesting example of the magnetic topological insulators is the Chern insulator (or quantum anomolous Hall insulator), which can be realized by breaking the TRS of a TI. In the second part of talk, I will present our recent finding of a ferromagnetic insulator. By depositing it on a TI, a Chern insulating state is found.
At the end, the possible applications of the above two magnetic topological systems in spintronics will be briefly discussed.