Spin- and angle-resolved inverse photoemission setup with spin orientation independent from electron incidence angle

TL;DR

This paper introduces a novel inverse photoemission setup with a low-energy, spin-polarized electron source that allows independent control of spin orientation and electron incidence angle, enabling detailed spin-resolved surface state studies.

Contribution

The setup's design decouples spin polarization from electron beam direction, and demonstrates tunable spin orientation with high energy and wavevector resolution for surface state analysis.

Findings

Successful measurement of Rashba splitting on Au(111) surface

Electron beam polarization can be tuned in three dimensions

Energy resolution comparable to photoemission techniques

Abstract

A new spin- and angle-resolved inverse photoemission setup with a low-energy electron source is presented. The spin-polarized electron source, with a compact design, can decouple the spin polarization vector from the electron beam propagation vector, allowing to explore any spin orientation at any wavevector in angle-resolved inverse photoemission. The beam polarization can be tuned to any preferred direction with a shielded electron optical system, preserving the parallel beam condition. We demonstrate the performances of the setup by measurements on Cu(001) and Au(111). We estimate at room temperature the energy resolution of the overall system to be $\sim170$ meV from $k_{B}T_{eff}$ of a Cu(001) Fermi level, allowing a direct comparison to photoemission. The spin-resolved operation of the setup has been demonstrated by measuring the Rashba splitting of the Au(111) Shockley surface state. The effective polarization of the electron beam is $P=30\pm3$ \% and the wavevector resolution is $\Delta k_{F}\lesssim0.06$ \AA$^{-1}$. Measurements on the Au(111) surface state demonstrate how the electron beam polarization direction can be tuned in the three spatial dimensions. The maximum of the spin asymmetry is reached when the electron beam polarization is aligned with the in-plane spin-polarization of the Au(111) surface state.