Multidimensional coherent spectroscopy of a semiconductor microcavity

Multidimensional coherent spectroscopy maps the detuning dependence of the upper (UP) and lower (LP) excitonpolariton branches¹ in a wedged microcavity with a single InGaAs quantum well at 5 K. Features on the diagonal correspond to intra-action coherences of the UP and LP branches. Off-diagonal peaks are interaction coherences between the UP and LP branches. With increasing detuning (Δ), all peaks move to higher energy, the exciton-like (E_EX) and cavity-like (E_γ) modes swap position and have maximum intensity near the anti-crossing at Δ=0. An isolated biexciton (B) is only seen at Δ<0, separated by a binding energy of approximately 2 meV. For Δ>0, the spectral weight of the off-diagonal features swap, as the LP and B come into resonance. This indicates that the off-diagonal features are sensitive to the interactions including two-quantum contributions and that a situation similar to a Feshbach resonance exists.² Polarization of two-quantum contributions show spin sensitive two-polariton and new biexciton correlations. The latter likely influence the Feshbach resonance between biexcitons and two-polariton states. The two-quantum signatures also demonstate that biexcitons perturb the light-matter coupling in the microcavity to reduce the mixed two-polariton contributions. Detuning dependence of zero-quantum contributions show Raman-like coherences that are enhanced near zero detuning. Asymmetry of the Raman coherences are indicative of many-body interactions, which also grow stronger as the light-matter interactions are enhanced near zero deuning.