Light-induced valley splitting and polarization of exciton-polaron in hole-doped monolayer WSe2

In this study we report light-induced energy splitting in valley exciton-polarons in hole-doped monolayer WSe₂ without magnetic field. In contrast to the optical stark effect using ultrashort light pulses, a 1-2 meV energy splitting between valleys is observed with continuous wave (CW) sub-milliwatt circular polarized excitation. We attribute the effect to light-induced valley/spin polarized hole carriers, which subsequently gives rise to valley contrast in energy position and oscillator strength of exciton polarons dressed in intervalley fashion. The picture is supported by optical power and gate dependent photoluminescence where the valley contrasts vanish in small optical power and large electrical doping settings. With the energy splitting and valley polarization information, we further estimate the induced valley-polarized hole density approaching10¹² cm^-2 and valley-contrast Fermi energy as 10 meV in monolayer WSe₂.