报告题目：Turning ‘off’ and ‘on’ the topological edge states in ultra-thin Na3Bi

报 告 人：Mark Edmonds，Monash University

报告时间：2018-10-16 10:00

报告地点：物理系理科楼C302

报告摘要：Na3Bi in bulk form represents a zero-bandgap topological Dirac semimetal (TDS), but when confined to few-layers is predicted to be a quantum spin Hall insulator with bulk bandgap of 300 meV.1 Furthermore, application of an electric field to few-layer Na3Bi has been predicted to induce a topological phase transition from conventional to topological insulator.2

I will discuss our efforts to grow epitaxial few-layer Na3Bi via molecular beam epitaxy, and probe its electronic structure and response to an electric field using scanning probe microscopy/spectroscopy and angle-resolved photoelectron spectroscopy. We are able to demonstrate that monolayer and bilayer Na3Bi are quantum spin Hall insulators with bandgaps >300 meV. Furthermore, via application of an electric field the bandgap can be tuned to semi-metallic and then re-opened as a conventional insulator with bandgap ~100 meV.3 The demonstration of an electric field tuned topological phase transition in ultra-thin Na3Bi provides a viable platform for the creation of a topological transistor.

References

[1] C. Niu et al., Phys. Rev. B (2017) 95, 075404

[2] H. Pan et al., Scientific Reports (2015) 5, 14639

[3] J. Collins et al., arXiv :1805.08378