Optical polarization and intervalley scattering in single layers of MoS2 and MoSe2.
Single layers of MoS2 and MoSe2 were optically pumped with circularly polarized light and an appreciable polarization was initialized as the pump energy was varied. The circular polarization of the emitted photoluminescence was monitored as a function of the difference between the excitation energy and the A-exciton emission at the K-point of the Brillouin zone. Our results show a threshold of twice the LA phonon energy, specific to the material, above which phonon-assisted intervalley scattering causes depolarization. In both materials this leads to almost complete depolarization within ~100 meV above the threshold energy. We identify the extra kinetic energy of the exciton (independent of whether it is neutral or charged) as the key parameter for presenting a unifying picture of the depolarization process.
Department of Materials Science and Technology, University of Crete, Heraklion Crete, 71003, Greece.|Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology Hellas (FORTH), Heraklion Crete, 71110, Greece.
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G
Kioseoglou
Materials Science &Technology Division, Naval Research Laboratory, Washington, DC 20375, USA.
A T
AT
Hanbicki
Optical Sciences Division, Naval Research Laboratory, Washington, DC 20375, USA.
M
M
Currie
Materials Science &Technology Division, Naval Research Laboratory, Washington, DC 20375, USA.
A L
AL
Friedman
Materials Science &Technology Division, Naval Research Laboratory, Washington, DC 20375, USA.
B T
BT
Jonker