  The effects caused by phonon-assisted tunnelling (PhAT) in a double quantum
dot (QD) molecule immersed in a cavity were studied under the quantum Markovian
master equation formalism in order to account for dissipation phenomena. We
explain how for higher PhAT rates, a stronger interaction between a QD and the
cavity at off-resonance takes place through the resonant interaction of another
QD and the cavity, where the QDs interact through tunnelling. A closer look at
the system's allowed optical transitions as a function of PhAT rates showed
coalescence of the transition energies, leading to a loss of spectroscopic
resolution in the photoluminescence (PL) spectrum. This coalescence occurs at
several exceptional points, suggesting a quantum dynamical phase transition.
