Progress in epitaxial thin-film Na3Bi as a topological electronic material

TL;DR

This review summarizes recent advances in the synthesis, characterization, and electronic properties of epitaxial Na3Bi thin films, highlighting their potential for topological electronics and the understanding of 3D Dirac semimetals.

Contribution

It provides a comprehensive overview of progress in epitaxial growth, electronic behavior, and phase transitions of Na3Bi thin films, emphasizing recent experimental and theoretical insights.

Findings

Successful synthesis of large-area Na3Bi thin films via molecular beam epitaxy.

Observation of thickness-dependent topological phase transitions.

Analysis of transport phenomena in doped Na3Bi films.

Abstract

Na3Bi was the first experimentally verified topological Dirac semimetal (TDS), and is a 3D analogue of graphene hosting relativistic Dirac fermions. Its unconventional momentum-energy relationship is interesting from a fundamental perspective, yielding exciting physical properties such as chiral charge carriers, the chiral anomaly, and weak anti-localization. It also shows promise for realising topological electronic devices such as topological transistors. In this review, an overview of the substantial progress achieved in the last few years on Na3Bi is presented, with a focus on technologically relevant large-area thin films synthesised via molecular beam epitaxy. Key theoretical aspects underpinning the unique electronic properties of Na3Bi are introduced. Next, the growth process on different substrates is reviewed. Spectroscopic and microscopic features are illustrated, and an analysis of semi-classical and quantum transport phenomena in different doping regimes is provided. The emergent properties arising from confinement in two dimensions, including thickness-dependent and electric-field driven topological phase transitions, are addressed, with an outlook towards current challenges and expected future progress.