Coherence of a spin-polarized electron beam emitted from a semiconductor photocathode in a transmission electron microscope

Abstract

The brightness and interference fringes of a spin-polarized electron beam extracted from a semiconductor photocathode excited by laser irradiation are directly measured via its use in a transmission electron microscope. The brightness was 3.8×107A cm-2sr-1 for a 30-keV beam energy with the polarization of 82%, which corresponds to 3.1×108A cm-2sr-1 for a 200-keV beam energy. The resulting electron beam exhibited a long coherence length at the specimen position due to the high parallelism of (1.7±0.3)×10-5rad, which generated interference fringes representative of a first-order correlation using an electron biprism. The beam also had a high degeneracy of electron wavepacket of 4×10-6. Due to the high polarization, the high degeneracy and the long coherence length, the spin-polarized electron beam can enhance the antibunching effect.