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

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Biography

Dr Mark Edmonds received his PhD 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 ???tunnelling microscopy (STM) and angle-resolved photoelectron ??spectroscopy (ARPES).