Determination of the complex microwave photoconductance of a single quantum dot - art. no. 035320

A small quantum dot containing approximately 20 electrons is realized in a two-dimensional electron system of an AlxGa1-xAs/GaAs heterostructure. Conv entional transport and microwave spectroscopy reveal the dot's electronic s tructure. By applying a coherently coupled two-source technique, we are abl e to determine the complex microwave-induced tunnel current. The amplitude of this photoconductance resolves photon-assisted tunneling (PAT) in the no nlinear regime through the ground state and an excited state as well. The o ut-of-phase component (susceptance) allows us to study charge relaxation wi thin the quantum dot on a time scale comparable to the microwave beat perio d.