Engineering electronic structure of a 2D topological insulator Bi(111) bilayer on Sb nanofilms by quantum confinement effect

TL;DR

This paper demonstrates the fabrication and electronic structure engineering of a 2D topological insulator Bi(111) bilayer on Sb nanofilms, revealing tunable topological edge states via quantum confinement effects.

Contribution

It introduces a novel fabrication method for Bi bilayer/Sb heterostructures and shows how quantum confinement induces topological edge states.

Findings

Observation of a 2D spinful massless electron gas in Bi bilayer

Emergence of topological edge states with reduced Sb thickness

Potential for low-energy electronics and spintronics applications

Abstract

We report on fabrication of a two-dimensional topological insulator-Bi(111) bilayer on Sb nanofilms via a sequential molecular beam epitaxy (MBE) growth technique. Our angle-resolved photoemission measurements demonstrate the evolution of the electronic band structure of the heterostructure as a function of the film thickness and reveal the existence of a two-dimensional spinful massless electron gas within the top Bi bilayer. Interestingly, Our first-principles calculation extrapolating the observed band structure shows that, by tuning down the thickness of the supporting Sb films into the quantum dimension regime, a pair of isolated topological edge states emerges in a partial energy gap at 0.32 eV above the Fermi level as a consequence of quantum confinement effect. Our results and methodology of fabricating nanoscale heterostructures establish the Bi bilayer/Sb heterostructure as a platform of great potential for both ultralow-energy-cost electronics and surface-based spintronics.