Mass acquisition of Dirac fermions in Cr-doped topological insulator Sb2Te3 films

TL;DR

This study demonstrates that doping Cr into Sb2Te3 thin films breaks time-reversal symmetry, induces a mass in Dirac surface states, and maintains high-quality Landau level spectra, advancing topological insulator research.

Contribution

It provides the first experimental evidence of mass acquisition in Dirac fermions in Cr-doped Sb2Te3, showing how magnetic doping affects surface state properties.

Findings

Cr doping induces a mass term in surface Dirac fermions.

High-quality Landau level spectra are preserved despite doping.

Mass magnitude correlates with Cr-doping level.

Abstract

We introduce time-reversal-symmetry breaking by doping Cr atoms into the topmost quintuple layer or into the bulk of Sb2Te3 thin films. We find that even at a high Cr-doping level the Landau level spectrum keeps a good quality, enabling the first demonstration of deviation of the zero-mode Landau level, induced by the acquisition of a mass term in the surface states in the presence of surface or bulk magnetic doping. The magnitude of the mass term in the surface states increases with increasing Cr-doping level. Our observation suggests Cr-doped Sb2Te3 is a promising candidate for the realization of the proposed novel magnetoelectric effects.