Exciton dynamics in WSe2 bilayers

TL;DR

This study explores exciton behavior in WSe2 bilayers using time-resolved photoluminescence, revealing distinct emission times for direct and indirect excitons and demonstrating polarization effects under laser excitation.

Contribution

It provides new insights into exciton dynamics, polarization, and energy dependence in WSe2 bilayers through time-resolved and polarization-resolved PL spectroscopy.

Findings

Direct exciton emission time ~ 3 ps

Indirect exciton emission time ~ 25 ps

Efficient optical orientation and alignment observed

Abstract

We investigate exciton dynamics in 2H-WSe2 bilayers in time-resolved photoluminescence (PL) spectroscopy. Fast PL emission times are recorded for both the direct exciton with $\tau_{D}$ ~ 3 ps and the indirect optical transition with $\tau_{i}$ ~ 25 ps. For temperatures between 4 to 150 K $\tau_{i}$ remains constant. Following polarized laser excitation, we observe for the direct exciton transition at the K point of the Brillouin zone efficient optical orientation and alignment during the short emission time $\tau_{D}$. The evolution of the direct exciton polarization and intensity as a function of excitation laser energy is monitored in PL excitation (PLE) experiments.