Coherent exciton-LO-phonon polarons in ZnSe quantum wells with strong confinement

摘要

We observe coherent exciton-LO-phonon polarons in a 3 nm ZnSe single quantum well using four-wave mixing with 30 fs light pulses. The formation of these superposition states is attributed to a strong LO-phonon coupling by the Frohlich interaction in a system in which the exciton binding exceeds the LO-phonon energy and the 2s exciton is nearly resonant with the LO-phonon energy. The rapid decay of these coherent quasipar-ticles is mainly attributed to the disintegration into zero-phonon excitons and free LO phonons as well as to the inhomogeneous broadening of LO-phonon energies due to disorder and k-space dispersion.