Fermi surface chirality induced in a TaSe$_{2}$ monosheet formed by a Ta/ Bi$_{2}$Se$_{3}$ interface reaction

TL;DR

This study demonstrates how a TaSe2 monosheet formed at a Bi2Se3 interface exhibits induced Fermi surface chirality and Rashba-like spin textures due to symmetry reduction, opening new avenues for chiral 2D electron systems.

Contribution

It introduces a novel interface reaction method to create a TaSe2 monosheet with reduced symmetry and induced spin textures on a topological insulator substrate.

Findings

Symmetry of TaSe2 monolayer is reduced from D3h to C3v.

In-plane spin components form helical Rashba-like textures.

Coupling of surface states with the Dirac cone observed.

Abstract

Spin-momentum locking in topological insulators and materials with Rashba-type interactions is an extremely attractive feature for novel spintronic devices and is therefore under intense investigation. Significant efforts are underway to identify new material systems with spin-momentum locking, but also to create heterostructures with new spintronic functionalities. In the present study we address both subjects and investigate a van der Waals-type heterostructure consisting of the topological insulator Bi$_{2}$Se$_{3}$ and a single Se-Ta-Se triple-layer (TL) of H-type TaSe$_{2}$ grown by a novel method which exploits an interface reaction between the adsorbed metal and selenium. We then show, using surface x-ray diffraction, that the symmetry of the TaSe2-like TL is reduced from D$_{3h}$ to C$_{3v}$ resulting from a vertical atomic shift of the tantalum atom. Spin- and angle-resolved photoemission indicates that, owing to the symmetry lowering, the states at the Fermi surface acquire an in-plane spin component forming a surface contour with a helical Rashba-like spin texture, which is coupled to the Dirac cone of the substrate. Our approach provides a new route to realize novel chiral two-dimensional electron systems via interface engineering that do not exist in the corresponding bulk materials.