Engineering three-dimensional topological insulators in Rashba-type spin-orbit coupled heterostructures

Tanmoy Das,A V Balatsky

doi:10.1038/ncomms2972

Abstract

Topological insulators represent a new class of quantum phase defined by invariant symmetries and spin-orbit coupling that guarantees metallic Dirac excitations at its surface. The discoveries of these states have sparked the hope of realizing non-trivial excitations and novel effects such as a magnetoelectric effect and topological Majorana excitations. Here we develop a theoretical formalism to show that a three-dimensional topological insulator can be designed artificially via stacking bilayers of two-dimensional Fermi gases with opposite Rashba-type spin-orbit coupling on adjacent layers, and with interlayer quantum tunneling. We demonstrate that in the stack of bilayers grown along a (001)-direction, a non-trivial topological phase transition occurs above a critical number of Rashba bilayers. In the topological phase, we find the formation of a single spin-polarized Dirac cone at the -point. This approach offers an accessible way to design artificial topological insulators in a set up that takes full advantage of the atomic layer deposition approach. This design principle is tunable and also allows us to bypass limitations imposed by bulk crystal geometry.

Highlights

Topological insulators represent a new class of quantum phase defined by invariant symmetries and spin-orbit coupling that guarantees metallic Dirac excitations at its surface
The unusual properties of topological insulators (TI) rely on synthesizing suitable materials that inherit various invariant symmetries and spin-orbit coupling in the bulk ground state, and that allow the formation of metallic Dirac fermions at the boundary[1,2,3,4,5,6]
Such an inverted band dispersion is well established in first-principle band structure calculations[26], and angle-resolved photoemission spectroscopy (ARPES) measurements[14]

Summary

Introduction

Topological insulators represent a new class of quantum phase defined by invariant symmetries and spin-orbit coupling that guarantees metallic Dirac excitations at its surface. We find the formation of a single spin-polarized Dirac cone at the G-point This approach offers an accessible way to design artificial topological insulators in a set up that takes full advantage of the atomic layer deposition approach. We propose here an alternative approach to design TIs by combining a set of layers of two-dimensional Fermi gases (2DFGs) with Rashba-type spin-orbit coupling. This twodimensional spin-orbit locked metallic state, in the presence of interlayer quantum tunneling, translates into a bulk insulator with Z2-invariant topological properties and Dirac excitations on the surface. Such TI will be free from any particular crystal geometry studied earlier.[25]

Methods

Results

Conclusion