Electrostatic Modulation of the Electronic Properties of Dirac Semimetal Na3Bi

TL;DR

This study demonstrates electrostatic control of electronic properties in Na3Bi Dirac semimetal thin films, showing high mobility, ambipolar behavior, and the influence of disorder and band structure on charge transport.

Contribution

It reports the growth of high-quality Na3Bi thin films on amorphous substrates and their electrostatic modulation, revealing new insights into Dirac semimetal transport properties.

Findings

High charge carrier mobility exceeding 7,000 cm²/Vs.

Observation of ambipolar field effect and minimum conductivity.

Hole mobility surpasses electron mobility due to band structure.

Abstract

Large-area thin films of topological Dirac semimetal Na$_3$Bi are grown on amorphous SiO$_2$:Si substrates to realise a field-effect transistor with the doped Si acting as back gate. As-grown films show charge carrier mobilities exceeding 7,000 cm$^2$/Vs and carrier densities below 3 $\times $10$^{18}$ cm$^{-3}$, comparable to the best thin-film Na$_3$Bi. An ambipolar field effect and minimum conductivity are observed, characteristic of Dirac electronic systems. The results are quantitatively understood within a model of disorder-induced charge inhomogeneity in topological Dirac semimetals. Due to the inverted band structure, the hole mobility is significantly larger than the electron mobility in Na$_3$Bi, and when present, these holes dominate the transport properties.