  We report nearly complete preservation of "spin memory" between optical
absorption and photoluminescence (PL) in nanometer slabs of GaSe pumped with up
to 0.2 eV excess energy. At cryogenic temperatures, the initial degree of
circular polarization ($\rho_0$) of PL approaches unity, with the major
fraction of the spin polarization decaying with a time constant $>$500 ps in
sub-100-nm GaSe nanoslabs. Even at room temperature, $\rho_0$ as large as 0.7
is observed, while pumping 1 eV above the band edge yields $\rho_0$ = 0.15.
Angular momentum preservation for both electrons and holes is due to the
separation of the non-degenerate conduction and valence bands from other bands.
In contrast to valley polarization in atomically thin transition metal
dichalcogenides, here optical spin polarization is preserved in nanoslabs of
100 layers or more of GaSe.
