2 research outputs found
Nonequilibrium stabilization of charge states in double quantum dots
We analyze the decoherence of charge states in double quantum dots due to
cotunneling. The system is treated using the Bloch-Redfield generalized master
equation for the Schrieffer-Wolff transformed Hamiltonian. We show that the
decoherence, characterized through a relaxation and a dephasing time
, can be controlled through the external voltage and that the
optimum point, where these times are maximum, is not necessarily in
equilibrium. We outline the mechanism of this nonequilibrium-induced
enhancement of lifetime and coherence. We discuss the relevance of our results
for recent charge qubit experiments.Comment: 5 pages, 5 figure
Nonlinear cotunneling through an artificial molecule
We study electron transport through a system of two lateral quantum dots
coupled in series. We consider the case of weak coupling to the leads and a
bias point in the Coulomb blockade. After a generalized Schrieffer-Wolf
transformation, cotunneling through this system is described using methods from
lowest-order perturbation theory. We study the system for arbitrary bias
voltages below the Coulomb energy. We observe a rich, non-monotonic behavior of
the stationary current depending on the internal degrees of freedom. In
particular, it turns out that at fixed transport voltage, the current through
the system is largest at weak-to-intermediate inter-dot coupling.Comment: 4 pages, 5 figure