學術演講
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2018-12-20 [Colloquium] Antiferromagnetic Topological Insulators Prof. Peng-Jen Chen,Institute of Physics, Academia Sinica, Taipei, Taiwan
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 Z 2 invariant, is protected by the time-reversal symmetry (TRS). That is to say, breaking of the TRS simultanesouly destroys the Z 2 topology. However, it is proposed that materials with specific antiferromagnetic configurations can still be classified into Z 2 topology due to the presence of a new protecting symmetry [1]. Since the theoretical proposal, no materials have been found to reveal this kind of topological phase. In this talk, I will demonstrate that pressurized SmB 6 , which is A-type antiferromagnetic, is a candidate for such antiferromagnetic Z 2 topological phase [2]. Possible applications in spintronics will be briefly discussed. Very recently, we
have found another G-type antiferromagnetic semiconductor that shows the antiferromagnetic Z 2 topological phase at ambient condition. Some preliminary results will be discussed.

References:
[1] R. S. K. Mong, A. M. Essin, and J. E. Moore, Phys. Rev. B 81, 245209 (2010).
[2] K. W. Chang and P. J. Chen, Phys. Rev. B 97, 195145 (2018).