Topological states and phase transitions in Sb$_2$Te$_3$-GeTe multilayers

TL;DR

This study experimentally investigates topological phase transitions in Sb$_2$Te$_3$-GeTe multilayers, revealing how layer thickness influences the emergence and hybridization of topological modes, enabling phase control.

Contribution

It provides the first experimental evidence of multiple topological modes in Sb$_2$Te$_3$-GeTe multilayers and demonstrates phase transitions driven by layer thickness and hybridization effects.

Findings

Multiple topological modes observed in multilayers.

Reducing GeTe layer thickness induces a phase transition.

Hybridization of states causes the transition.

Abstract

Topological insulators (TIs) are bulk insulators with exotic 'topologically protected' surface conducting modes. It has recently been pointed out that when stacked together, interactions between surface modes can induce diverse phases including the TI, Dirac semimetal, and Weyl semimetal. However, currently a full experimental understanding of the conditions under which topological modes interact is lacking. Here, working with multilayers of the TI Sb$_2$Te$_3$ and the band insulator GeTe, we provide experimental evidence of a multiple topological modes in a single Sb$_2$Te$_3$-GeTe-Sb$_2$Te$_3$ structure. Furthermore, we show that reducing the thickness of the GeTe layer induces a phase transition from a Dirac-like phase to a gapped phase. By comparing different multilayer structures we demonstrate that this transition occurs due to the hybridisation of states associated with different TI films. Our results demonstrate that the Sb$_2$Te$_3$-GeTe system offers strong potential towards manipulating topological states as well as towards controlledly inducing various topological phases.