Splitting of the topologically-protected Dirac cone without breaking time reversal symmetry

TL;DR

This paper demonstrates that interactions at the interface of topological insulators and semiconductors can cause the Dirac cone to split and break particle-hole symmetry without breaking time reversal symmetry, revealing new physics.

Contribution

The paper introduces a general model showing how TI-semiconductor interactions can alter surface states without topological transitions or symmetry breaking.

Findings

Dirac cone can split into two due to interface interactions

Particle-hole symmetry can be fundamentally broken

Model predictions are supported by first-principles calculations

Abstract

Topological insulators (TIs) are a new class of matter characterized by the unique electronic properties of an insulating bulk and metallic boundaries arising from non-trivial bulk band topology. While the surfaces of TIs have been well studied, the interface between TIs and semiconductors may not only be more technologically relevant but the interaction with non-topological states may fundamentally alter the physics. Here, we present a general model to show that such an interaction can lead to spin-momentum locked non-topological states, the Dirac cone can split in two, and the particle-hole symmetry can be fundamentally broken, along with their possible ramifications. Unlike magnetic doping or alloying, these phenomena occur without topological transitions or the breaking of time reversal symmetry. The model results are corroborated by first-principles calculations of the technologically relevant Bi$_2$Se$_3$ film van der Waals bound to a Se-treated GaAs substrate.