Theory of phonon-assisted intraband transitions in semiconductor quantum dots

The investigation of the intersubband dynamics occurring in the conduction band of doped semiconductor quantum dots (QD's) has emerged as a powerful tool to probe their electronic structure and properties. Here, the temperature, the dephasing and the relaxation dynamics are of interest, both from a fundamental point of view but also regarding the performance of QD-based optoelectronic devices. Whereas the lineshape of QD interband transitions is well described by the independent boson model treating a diagonal electron-phonon coupling. For intraband transitions both diagonal and non-diagonal electron-phonon coupling are relevant. Typically, such problems involving diagonal and non-diagonal coupling are treated within approximate or perturbative approaches. Here, we present a fully quantized theory to calculate the coupled electron-phonon dynamics based on a non-perturbative equation of motion approach reproducing also correct results for limits of known exactly solvable models.