Exploring optical spin polarization in gallium telluride (GaTe) via circularly polarized photoluminescence

초록

Gallium Telluride (GaTe) has garnered significant attention for its unique optical properties, yet its potential for optical spin polarization driven by triplet excitonic states analogous to those in GaSe remains largely unexplored. In this study, we investigate the optical spin polarization in GaTe through circularly polarized photoluminescence (CPPL) measurements at both room and cryogenic temperatures. Notably, a typical GaTe flake exhibited a robust degree of circular polarization (DoCP) of approximately 70% at 77 K under 633 nm laser excitation. The DoCP was found to depend strongly on flake thickness, showing no clear trend for flakes thinner than 25 nm, while flakes thicker than 25 nm exhibited a pronounced decrease in DoCP, attributed to the increasing exciton photoluminescence (PL) decay lifetime z0 relative to the spin relaxation time zs. The DoCP also varied significantly with excitation wavelength: for a 163 nm thick flake, the DoCP was 25% under 633 nm excitation but dropped to 5% when excited at 532 nm. Temperature dependence studies further revealed a nonmonotonic behavior of the DoCP, linked to the interplay between exciton PL decay lifetime z0 and spin relaxation time zs. These findings highlight the complex spin dynamics in GaTe and its potential applications in spintronic devices.

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