Gate-tunable quantum oscillations in ambipolar Cd3As2 thin films

TL;DR

This study demonstrates gate-tunable quantum oscillations and a transition from band to hopping conduction in ultrathin Cd3As2 films, revealing new electronic properties and potential for nanoelectronic applications.

Contribution

First observation of gate-induced conduction transition and quantum oscillations in Cd3As2 thin films, with insights into their band structure and quantum effects.

Findings

Gate-induced transition from band to hopping conduction

Observation of gate-tunable Shubnikov-de Haas oscillations

Evidence of bandgap opening in thin films

Abstract

Electrostatic doping in materials can lead to various exciting electronic properties, such as metal-insulator transition and superconductivity, by altering the Fermi level position or introducing exotic phases. Cd3As2, a three-dimensional (3D) analog of graphene with extraordinary carrier mobility, was predicted to be a 3D Dirac semimetal, a feature confirmed by recent experiments. However, most research so far has been focused on metallic bulk materials that are known to possess ultra-high mobility and giant magnetoresistance but limited carrier transport tunability. Here, we report on the first observation of a gate-induced transition from band conduction to hopping conduction in single-crystalline Cd3As2 thin films via electrostatic doping by solid electrolyte gating. The extreme charge doping enables the unexpected observation of p-type conductivity in a 50 nm-thick Cd3As2 thin film grown by molecular beam epitaxy. More importantly, the gate-tunable Shubnikov-de Haas (SdH) oscillations and the temperature-dependent resistance reveal a unique band structure and bandgap opening when the dimensionality of Cd3As2 is reduced. This is also confirmed by our first-principles calculations. The present results offer new insights towards nanoelectronic and optoelectronic applications of Dirac semimetals in general, and provide new routes in the search for the intriguing quantum spin Hall effect in low-dimension Dirac semimetals, an effect that is theoretically predicted but not yet experimentally realized.