Characterization of electron spin polarization from positive electron affinity GaAs photocathodes
Abstract
Negative Electron Affinity (NEA) GaAs photocathodes are widely used to generate spin-polarized electron beams, typically achieving Electron Spin Polarizations (ESPs) in the range of 35%–40%. However, when operated in a Positive Electron Affinity (PEA) state, where a potential barrier inhibits low-energy electrons from escaping into vacuum, measured ESPs can exceed 50%. This effect can occur naturally during photocathode operation, as the NEA surface activation layers can degrade easily over time, increasing the electron affinity. In this work, we investigate and characterize the behavior of enhanced ESPs under PEA conditions. We present experimental measurements of ESP using a retarding-field Mott polarimeter on GaAs photocathodes with controlled and varying electron affinities. These results are complemented by theoretical explanations considering the material band structure, the light excitation profile, and spin depolarization mechanisms.
Article Details
Journal Info
Journal of Applied Physics
American Institute of Physics
Authors (9)
S. J. Levenson
Cornell Laboratory for Accelerator-Based Sciences and Education (CLASSE), Cornell University 1 , Ithaca, New York 14850,
M. B. Andorf
Cornell Laboratory for Accelerator-Based Sciences and Education (CLASSE), Cornell University 1 , Ithaca, New York 14850,
M. A. Reamon
Cornell Laboratory for Accelerator-Based Sciences and Education (CLASSE), Cornell University 1 , Ithaca, New York 14850,
B. Vareskic
Department of Physics, Cornell University 2 , Ithaca, New York 14853,
A. Galdi
Department of Industrial Engineering, University of Salerno 6 , 84084 Fisciano, SA,
O. Chubenko
Department of Physics, Northern Illinois University 4 , DeKalb, Illinois 60115,
J. Callahan
Department of Physics, Northern Illinois University 4 , DeKalb, Illinois 60115,
J. M. Maxson
Cornell Laboratory for Accelerator-Based Sciences and Education (CLASSE), Cornell University 1 , Ithaca, New York 14850,
I. V. Bazarov
Cornell Laboratory for Accelerator-Based Sciences and Education (CLASSE), Cornell University 1 , Ithaca, New York 14850,