Decay And Persistence Of Spatial Coherence During Phonon-Assisted Relaxation In Double Quantum Dots

We present a theoretical study of the evolution of spatial coherence during intraband relaxation between exciton states in a pair of vertically stacked semiconductor quantum dots coupled to acoustic phonons. We show that spatial coherence can be transferred to the ground state even in a system of uncoupled nonidentical quantum dots if a particular kind of degeneracy between the interlevel energy splittings is present. The phonon-assisted mechanism of coherence transfer leads to a dependence of the amount of the resulting coherence on the interdot distance and temperature. We analyze also the impact of carrier-phonon dynamics on a coupled system, where spatial coherence is present in the delocalized ground state.