Theory of time-dependent transport in quantum dot systems

The formulation of the time-dependent tunnel current in quantum dot (QD) systems in the (generalized) transfer Hamiltonian formalism is reconsidered, taking into account the nonorthogonality between the subsystems. Exploiting the fact that only the total charge in the system is conserved, in general, gives rise to a new formulation of the transport theory. As a result, it is shown necessary to depart from the orthodox picture, in which the current is treated as a local property of the system. A general formula for the current is derived. By expressing properties of the quantum dot in the Hubbard I approximation with the loop correction, thereby including strong correlations of the QD states, numerical results are given for various time-dependent source-drain voltages. (C) 2003 Wiley Periodicals, Inc.