Topological Anderson Insulator: Theory and Experiments
- Speaker: Prof. Shen, Shun-Qing (University of Hong Kong)
- Date: Wednesday July 24, 2019 05:00pm
- Place: Jungho Seminar Room
Abstract
Topological Anderson insulator is a novel quantum state of matter, which was predicted by Shen and his collaborators in 2009. Usually a topological insulator is robust against disorders in the band gap of electronic band structure. Strong disorders close the band gap and make all states localized to form Anderson insulator. Topological Anderson insulator is a surprising discovery that sufficient disorder can drive a trivial insulator into a topologically non-trivial insulator in which protected edge states emerge, leading quantized transport in two dimensions. Disorder, besides causing Anderson localization of bulk electronic states, is fundamentally responsible for inducing nontrivial topology order into the system, and hence creating protected edge modes in a mobility gap instead of a band gap. This work has opened a new direction in studying the nontrivial interplay between disorder and topological order. Since then the discovery has since triggered relevant works in a variety of systems such as topological insulators of different dimensions (PRL 2010), topological superconductors (PRB 2016) and photonic crystals (PRL 2013). Very recently, the discovery was confirmed experimentally by Szameit and Segev groups from Germany and Israel in photonic crystals (Nature 560, 461 (2018)) and Gadway and Massignnan groups from USA and Spain in cold atoms (Science 262, 929(2018)), respectively. The experimental demonstration of the topological Anderson insulator shows that disorder can enhance robust topological transport rather than arrest it. Besides, the photonic crystal and cold atoms are two completely different platforms. Observation of topological Anderson insulator in these two systems show that the phenomenon is quite general, emerging across a large range of disordered systems.
References
- Topological Anderson insulator, J. Li, R. L. Chu, J. K. Jain & S. Q. Shen, Physical Review Letters 102, 136806 (2009)
- Photonic topological Anderson insulators, S. Stutzer et al., Nature 560, 461 (2018)
- Observation of the topological Anderson insulator in disordered atomic wires, E. J. Meier et al., Science 262, 929 (2018)