Optical Spin Polarization Dynamics in GaSe Nanoslabs

TL;DR

This study demonstrates near-complete optical spin polarization preservation in GaSe nanoslabs across a range of temperatures and excitation energies, highlighting unique spin dynamics distinct from other 2D materials.

Contribution

It reveals that GaSe nanoslabs maintain high spin polarization over long timescales, even at room temperature, due to band separation, which is a novel finding compared to similar materials.

Findings

High initial circular polarization at cryogenic temperatures

Significant spin memory retention at room temperature

Optical spin polarization preserved 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 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.