Impact of dark superpositions on the relaxation dynamics of an optically driven phonon-coupled exciton-biexciton quantum-dot system

Abstract

Within a numerically complete real-time path integral approach we identify the realization of dark superpositions as a general mechanism that strongly modifies the quantum dissipative relaxation of an optically driven quantum dot coupled to acoustic phonons. The presence of dark superpositions in an exciton-biexciton system that can be controlled by varying the laser polarization is shown to have a significant impact on the stationary values of the electronic occupations as well as on the precedent relaxation dynamics. Similar to the critical slowing down that is known to occur near phase transitions the time to reach a stationary state rises with no limit for polarizations that nearly realize a dark superposition. Interestingly, this time may show a nonmonotonic temperature dependence caused by a crossover between coherent and incoherent relaxation dynamics.