A theoretical approach to tunneling processes in quantum structures

A theoretical framework for the electrical transport through quantum struct ures (QS) is proposed based on Keldysh Green's function. It is our purpose to develop a new analytic method which is applicable in the situation where the higher order effects of the elastic and the inelastic scattering proce sses are essential. We derive a general formula for the current through QS and find new components of co-tunneling current proportional to V-2 and V i n addition to term at T = 0 K resulting from electron correlation between d ifferent charge states.