Figure 3: Exciton-selective optical Stark effect controlled by light polarization.

(a,b) Equilibrium absorption spectra with light polarization angle of θ=20° (top panel in a) and θ=90° (top panel in b). Black dots (middle panels) and gray dots (bottom panels) are transient DT spectra at τ=0 fs with co-polarized and cross-polarized pump-probe configurations, respectively. Probe polarization angles are fixed at θ=20° (a) and θ=90° (b). Pump photon energy is 1.44 eV with fluence of 230 μJ cm⁻². The blue- (red-) shaded area represents the spectral region where DT signal is dominated by the shift of the X₁ (X₂) state. (c,d) Pump-polarization-dependent optical Stark shifts of X₁ (blue dots in c) and X₂ (red dots in d) with fixed probe polarizations of θ=20° and θ=90°, respectively. The solid lines are fits.