Spin-dependent quantum interference in photoemission process from spin-orbit coupled states

Koichiro Yaji,Chuangtian Chen,Sogen Toyohisa,Katsuyoshi Kobayashi,Ayumi Harasawa,Yukiaki Ishida,Kenta Kuroda,Fumio Komori,Shuntaro Watanabe,Shik Shin

doi:10.1038/ncomms14588

Abstract

Spin–orbit interaction entangles the orbitals with the different spins. The spin–orbital-entangled states were discovered in surface states of topological insulators. However, the spin–orbital-entanglement is not specialized in the topological surface states. Here, we show the spin–orbital texture in a surface state of Bi(111) by laser-based spin- and angle-resolved photoelectron spectroscopy (laser-SARPES) and describe three-dimensional spin-rotation effect in photoemission resulting from spin-dependent quantum interference. Our model reveals that, in the spin–orbit-coupled systems, the spins pointing to the mutually opposite directions are independently locked to the orbital symmetries. Furthermore, direct detection of coherent spin phenomena by laser-SARPES enables us to clarify the phase of the dipole transition matrix element responsible for the spin direction in photoexcited states. These results permit the tuning of the spin polarization of optically excited electrons in solids with strong spin–orbit interaction.

Highlights

Spin–orbit interaction entangles the orbitals with the different spins
The entangled spin–orbital textures on a topological insulator, Bi2Se3, and a Rashba-type ternary alloy, BiTeI14,15, were revealed experimentally and theoretically; the spin texture is locked to the orbital texture of the bands
We report on the spin–orbital texture of a surface state of an elemental Bi(111), which was considered to show the single-chiral spin texture[16,17,18], investigated by spin- and angleresolved photoelectron spectroscopy using a vacuum ultraviolet laser

Summary

Introduction

Spin–orbit interaction entangles the orbitals with the different spins. The spin–orbitalentangled states were discovered in surface states of topological insulators. Direct detection of coherent spin phenomena by laser-SARPES enables us to clarify the phase of the dipole transition matrix element responsible for the spin direction in photoexcited states. These results permit the tuning of the spin polarization of optically excited electrons in solids with strong spin–orbit interaction. In a standard model of the spin texture on the spin–orbit-coupled materials, the spin is locked to the momentum of an electron, resulting in a single-chiral spin texture[5,7]. The spin–orbital-entangled systems are one of the promising candidates[19] to realize the spin manipulation of optically excited electrons[20,21,22]

Methods

Results

Conclusion