Invited Paper 2D+EM+MN+NS-WeA9
Electronic Properties of Ultra-Thin Na₃Bi: A Platform for a Topological Transistor

Wednesday, October 23, 2019, 5:00 pm, Room A216

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 demonstrate that monolayer and bilayer Na₃Bi are wide bandgap quantum spin Hall insulators (E_G>300 meV) that can be tuned with an electric field to semi-metallic, and at higher electric fields re-opened as a conventional insulator.³ This is the first experimental demonstration of such an electric field tuned topological phase transition in any material. Finally, I will discuss our most recent efforts to perform transport measurements on few-layer Na₃Bi at doping levels corresponding to bulk conduction and edge conduction, with and without an applied magnetic field.

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., Nature 564, 390 (2018)