Master equation techniques for exciton motion, relaxation, capture and annihilation

V. M. Kenkre

Dara P. S. McCutcheon, Nikesh S. Dattani, Erik M. Gauger +2 more

We develop a versatile master equation approach to describe the nonequilibrium dynamics of a two-level system in contact with a bosonic environment, which allows for the exploration of a wide range of parameter regimes within a single formalism. As an experimentally relevant example, we apply this technique to the study of excitonic Rabi rotations in a driven quantum dot, and compare its predictions to the numerical Feynman integral approach. We find excellent agreement between the two methods across a generally difficult range of parameters. In particular, the variational master equation technique captures effects usually considered to be nonperturbative, such as multiphonon processes and bath-induced driving renormalization, and can give reliable results even in regimes in which previous master equation approaches fail.

Nicholas E. Geacintov, Jacques Breton

Andrey R. Kolovsky

This paper discusses the master equation approach to the derivation of the Esaki-Tsu equation for drift current. It is shown that the relaxation term in the master equation can be identified by measuring the velocity distribution of the carriers. We also show that the standard form of the relaxation term, used earlier to derive the Esaki-Tsu equation, predicts unphysical velocity distribution. We suggest a more elaborate relaxation term, which is argued to correctly capture the effect of a bosonic bath in experiments on atomic current in optical lattices.