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.
Categories: cond-mat.mtrl-sci