Tunable Dirac interface states in topological superlattices

TL;DR

This paper demonstrates a tunable platform for Dirac interface states in topological superlattices, enabling continuous control of Dirac mass through temperature, which opens new avenues for engineering quantum states of matter.

Contribution

It introduces a novel experimental and theoretical platform using Pb1-xSnxSe superlattices where Dirac interface states can be continuously tuned, a significant advancement over previous fixed-mass systems.

Findings

Dirac states occur at interfaces between topological and trivial insulators.

The Dirac mass can be tuned continuously with temperature.

Magnetooptical spectroscopy confirms the tunability of interface states.

Abstract

Relativistic Dirac fermions are ubiquitous in condensed matter physics. Their mass is proportional to the material energy gap and the ability to control and tune the mass has become an essential tool to engineer quantum phenomena that mimic high energy particles and provide novel device functionalities. In topological insulator thin films, new states of matter can be generated by hybridizing the massless Dirac states that occur at material surfaces. In this work, we experimentally and theoretically introduce a platform where this hybridization can be continuously tuned: the Pb1-xSnxSe topological superlattice. In this system, topological Dirac states occur at the interfaces between a topological crystalline insulator Pb1-xSnxSe and a trivial insulator, realized in the form of topological quantum wells (TQW) epitaxially stacked on top of each other. Using magnetooptical transmission spectroscopy on high quality MBE grown Pb1-xSnxSe superlattices, we show that the penetration depth of the TQW interface states and therefore their Dirac mass is continuously tunable with temperature. This presents a new pathway to engineer the Dirac mass of topological systems and paves the way towards the realization of emergent quantum states of matter using Pb1-xSnxSe topological superlattices.