Nonequilibrium Transport Properties through Two Quantum Dots

Nonequilibrium transport properties are studied in an array of two quantum dots connected in series, taking account of the long-range charging effect. The current and its fluctuation are calculated by solving the Master equation. At low bias voltages, we propose two types of transport; one is a regular motion of charges, one by one, which corresponds to the minimum of the current fluctuation, and the other is an irregular motion, which corresponds to a local maximum. Their interplay results in new rich structures of the Coulomb blockade current oscillation, as a function of the gate voltage. With increasing bias voltage, the current fluctuation goes to a constant level which is one third of the classical shot noise.