Two-electron Quantum Dot System Tunneling Microscopic Theory Research

Due to zero dimensionality and quantized energy levels, properties of electron transport in quantum dots have been studied extensively. Within the semi-classic framework of phenomenological models, semi-conductor quantum dots are usually modeled as simple semi-classic capacitors to explain Coulomb blockade effect and other spin related transport phenomena. However electron-electron interaction, especially the correlation effects, may require a approach more delicate than the conventional ones to be dealt with.A microscopic theory is presented for electron cotunneling through doubly occupied quantum dots in the Coulomb blockade regime. Beyond the semi-classic framework of phenomenological models, an fully quantum mechanical solution for cotunneling and sequential tunneling of electrons through a one-dimensional quantum dot is obtained. It is revealed that the cotunneling conductance exhibits strong dependence on the spin configuration of the electrons confined inside the dot. Especially for the triplet configuration, the conductance shows an obvious deviation from the well-known quadratic dependence on the applied bias voltage.