Search for spin-polarized photoemission from GaAs using light with orbital angular momentum

Laser light with photon energy near the band gap of GaAs and in Laguerre-Gaussian modes with different amounts of orbital angular momentum was used to produce photoemission from unstrained GaAs. The degree of electron spin polarization was measured using a micro-Mott polarimeter and found to be consistent with zero with an upper limit of \ensuremath{\sim}3$%$ for light with up to $\ifmmode\pm\else\textpm\fi{}5\ensuremath{\hbar}$ of orbital angular momentum. In contrast, the degree of spin polarization of 32.3 \ifmmode\pm\else\textpm\fi{} 1.4$%$ using circularly polarized laser light at the as the same wavelength, which is typical for bulk GaAs photocathodes.