Optical Spin Polarization Dynamics in GaSe Nanoslabs

Abstract

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.

arXiv comment6 pages, 5 figures

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• Spin splitting in 2D monochalcogenide semiconductors
• Symmetry, distorted bandstructure, and spin-orbit coupling of (group-III) metal-monochalcogenide monolayers
• Layer- and Frequency-Dependent Second Harmonic Generation in Reflection from GaSe Atomic Crystals
• Control of excitonic absorption by thickness variation in few-layer GaSe
• Exciton spin dynamics in GaSe
• Linearly polarized remote-edge luminescence in GaSe nanoslabs
• Layer-dependent optically-induced spin polarization in InSe
• Bound exciton and free exciton states in GaSe thin slab