Anisotropic Quantum Confinement Effect and Electric Control of Surface States in Dirac Semimetal Nanostructures

TL;DR

This paper theoretically studies how quantum confinement and electric gating influence the electronic and surface states in Dirac semimetal nanostructures, revealing anisotropic effects and controllable topological surface states for device applications.

Contribution

It uncovers the anisotropic quantum confinement effects and demonstrates electric control of surface states in Dirac semimetal nanostructures, advancing topological device design.

Findings

Quantum confinement opens a bulk band gap at Dirac points.

Confinement along different directions shows strong anisotropic effects.

Lateral electrostatic gating can control topological surface states.

Abstract

The recent discovery of Dirac semimetals represents a new achievement in our fundamental understanding of topological states of matter. Due to their topological surface states, high mobility, and exotic properties associated with bulk Dirac points, these new materials have attracted significant attention and are believed to hold great promise for fabricating novel topological devices. For nanoscale device applications, effects from finite size usually play an important role. In this report, we theoretically investigate the electronic properties of Dirac semimetal nanostructures. Quantum confinement generally opens a bulk band gap at the Dirac points. We find that confinement along different directions shows strong anisotropiceffects. In particular, the gap due to confinement along vertical c-axis shows a periodic modulation, which is absent for confinement along horizontal directions. We demonstrate that the topological surface states could be controlled by lateral electrostatic gating. It is possible to generate Rashba-like spin splitting for the surface states and to shift them relative to the confinement-induced bulk gap. These results will not only facilitate our fundamental understanding of Dirac semimetal nanostructures, but also provide useful guidance for designing all-electrical topological spintronics devices.