Direct observation of quantum confinement of massless Dirac fermions in a topological insulator

TL;DR

This paper reports the direct visualization of quantum confinement of massless Dirac fermions in a topological insulator using a specially grown heterostructure, revealing true Dirac quantum corrals and analyzing quasiparticle lifetimes.

Contribution

It demonstrates the realization of a true Dirac quantum corral by heteroepitaxially growing Bi bilayers on Bi2Te3, enabling direct observation of quantum interference of massless Dirac fermions.

Findings

Successful visualization of quantum interference in Dirac fermion corrals

Identification of perfect boundary orientation matching for confinement

Systematic measurement of quasiparticle lifetime of confined Dirac fermions

Abstract

Since the discovery of topological insulators (TIs)1,2, the peculiar nature of their chiral surface states has been experimentally demonstrated both in bulk and in film materials with open boundaries3,4. Closed boundary on a TI surface may intrigue more interesting phenomena such as quantum confinement of massless Dirac fermions (DFs), which is analogous to the quantum corral (QC) for massive free electrons on a metal surface5-10. To date, it keeps a highly stringent challenge to realize a true Dirac QC due to the unusual transmitting power of a massless fermion. Through heteroepitaxially growing a Bi bilayer on the Bi2Te3 surface with appropriate coverage, here we demonstrate the realization of a true Dirac QC. Specifically, spectacular maps of quantum interference in equilateral triangle-shaped QCs surrounded by Bi bilayers are directly visualized by using a low-temperature scanning tunneling microscope. The present success is ascribed to a perfect orientation matching between the QC boundary and the stationary-phase scattering of massless DFs. In addition, the quasiparticle lifetime of the confined DFs is also systematically measured and analyzed.