Exciton Valley Dynamics probed by Kerr Rotation in WSe2 Monolayers

Abstract

We have experimentally studied the pump-probe Kerr rotation dynamics in WSe${}_2$ monolayers. This yields a direct measurement of the exciton valley depolarization time ${\tau }_v$. At T=4K, we find ${\tau }_v\approx 6$ps, a fast relaxation time resulting from the strong electron-hole Coulomb exchange interaction in bright excitons. The exciton valley depolarization time decreases significantly when the lattice temperature increases with ${\tau }_v$ being as short as 1.5ps at 125K. The temperature dependence is well explained by the developed theory taking into account the exchange interaction and a fast exciton scattering time on short-range potentials.

5 pages, 3 figures

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• Valley polarization in MoS2 monolayers by optical pumping
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• Tightly bound excitons in monolayer WSe2
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
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