Near Unity Optical Spin Polarization in GaSe Nanoslabs

TL;DR

This study demonstrates near-unity optical spin polarization in GaSe nanoslabs, maintaining high spin memory at cryogenic and room temperatures, due to band structure properties that preserve angular momentum during optical processes.

Contribution

It reveals that GaSe nanoslabs can sustain high degrees of optical spin polarization across multiple layers, unlike atomically thin TMDs, due to their unique band separation.

Findings

Near-unity spin polarization at cryogenic temperatures.

High spin polarization (up to 0.7) at room temperature.

Spin preservation in multilayer GaSe nanoslabs.

Abstract

We report nearly complete preservation of "spin memory" between optical absorption and photoluminescence (PL) in nanometer slabs of GaSe pumped with 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 TMDs, here optical spin polarization is preserved in nanoslabs of 100 layers or more of GaSe.