Turning ‘off’ and ‘on’ the topological edge states in ultra-thin Na3Bi

19/10/2018 @ 3:00 PM – 4:00 PM Asia/Singapore Timezone
S16 Level 6 – Theory Common Conference Room
6 Science Drive 2
Singapore 117546
Turning ‘off’ and ‘on’ the topological edge states in ultra-thin Na3Bi @ S16 Level 6 – Theory Common Conference Room | Singapore | Singapore

Speaker: Dr Mark Edmonds
Affiliation: Monash University
Host: Assist. Prof. Lu Jiong
Location: Click HERE for directions

Abstract Details: 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 a 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.

About the Speaker: Dr Mark Edmonds received his Ph.D. from La Trobe University in 2014. From 2014-2016 he was a postdoc fellow at Monash University working with Prof. Michael Fuhrer. In 2016 he was awarded an Australian Research Council Discovery Early Career Research Award to realise novel electronic phases in two-dimensional materials and is now a lecturer in the Department of Physics and Astronomy at Monash University. His research focuses on the growth and characterization of novel electronic materials for the development of next-generation electronic devices, using spectroscopic tools such as scanning tunneling microscopy (STM) and angle-resolved photoelectron spectroscopy (ARPES).