Exciton dynamics in WSe 2 bilayers

© 2014 AIP Publishing LLC. We investigate exciton dynamics in WSe2 bilayers in time-resolved photoluminescence (PL) spectroscopy. Fast PL emission times are recorded for both the direct exciton with τ D ≲3 ps and the indirect optical transition with τ I≈25 ps. For temperatures between 4 to 150 K τ 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 τ D. The evolution of the direct exciton polarization and intensity as a function of excitation laser energy is monitored in PL excitation experiments.