Author: Lukashev, P.
Paper Title Page
WEPAB102 Half-Metal Spin Filter for Highly Polarized Emission from GaAs Photocathodes 2833
 
  • S. Poddar, C.-J. Jing, E.J. Montgomery
    Euclid Beamlabs, Bolingbrook, USA
  • P. Lukashev
    University of Northern Iowa, Cedar Falls, Iowa, USA
  • C. Palmstrøm
    UCSB, Santa Barbara, California, USA
  • M.L. Stutzman, S. Zhang
    JLab, Newport News, Virginia, USA
 
  Funding: Work supported by Department of Energy grant number DE-SC0020564.
GaAs-based photocathodes are one of the major sources of spin-polarized electrons and are crucial for the upcoming Electron-Ion collider experiments which includes study of proton spin and spin parity violation in the standard model. The theoretical polarization limit in unstrained GaAs photocathodes is 50 % but only 35 % is routinely achieved in experiments. Spin selective filtering allows to boost the spin polarization beyond the 50 % theoretical limit. In this work, first-principle electronic calculations using standard Density Functional Theory are performed to predict possible Heusler alloy half-metal candidates to be used as spin-filter. Simulations are also performed to investigate the half-metallicity as function of the magnetic spin direction. Several devices are experimentally fabricated using dedicated Molecular Beam Epitaxy growth system. We implemented Quantum Efficiency and Polarization testing of these half-metal/GaAs heterostructures using a dedicated Mott polarimeter system. Photoemission can also be seen on magnetically switching the spin-filter direction accompanied by a change in sign of the asymmetry which is a qualitative proof of the spin-filtering effect.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB102  
About • paper received ※ 20 May 2021       paper accepted ※ 28 July 2021       issue date ※ 27 August 2021  
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