Visualization of optical polarization transfer to photoelectron spin vector emitted from the spin-orbit coupled surface state

TL;DR

This study demonstrates how laser polarization can be used to control and visualize the three-dimensional spin vector of photoelectrons emitted from Bi2Se3 surface states, enabling optical manipulation of spin states.

Contribution

We introduce a laser-SARPES technique with 3D spin detection and tunable polarization to directly visualize and control photoelectron spin orientation via optical phase and polarization.

Findings

Optical phase and polarization control the photoelectron spin direction.

Laser-SARPES enables direct visualization of spin vector changes.

Potential for optically controlled spin-polarized electron sources.

Abstract

Similar to light polarization that is selected by a superposition of optical basis, electron spin direction can be controlled through a superposition of spin basis. We investigate such a spin interference occurring in photoemission of the spin-orbit coupled surface state in Bi2Se3 by using spin- and angle-resolved photoemission spectroscopy combined with laser light source (laser-SARPES). Our laser-SARPES with three-dimensional spin detection and tunable laser polarization including elliptical and circular polarization enables us to directly visualize how the direction of the fully-polarized photoelectron spin changes according to the optical phase and orientation of the incident laser polarization. By this advantage of our laser-SARPES, we demonstrate that such optical information can be projected to the three-dimensional spin vector of the photoelectrons. Our results, therefore, present a novel spin-polarized electron source permitting us to optically control the pure spin state pointing to the arbitrary direction.