Charging time effects and transient current beats in horizontal and vertical quantum dot systems

• We consider transient effects in different configurations of quantum dots system.
• The charging time of the QDs wire increases linearly with the wire length.
• The system geometry hardly influences the wire charging time for large voltages.
• Transient current beats patterns strongly depend on the wire inter-site couplings.
• The Coulomb interactions reduce the oscillations of the current beats.

The transient electric current and quantum dot (QD) occupation probabilities in a linear wire of N quantum dots coupled with two leads are investigated theoretically for vertical (T-shaped) and horizontal geometries of QDs. The model tight-binding Hamiltonian with inter-dot Coulomb interactions and the equation of motion technique are used in our calculations. The charging time of the initially empty wire is analyzed. It turns out that for both wire configurations the QD charging time grows up linearly for subsequent dots with simultaneously decreasing rate of the charging process, except the N-th dot. We have also shown that the transient current beats appearing in response to the sudden change of the bias voltage exhibit different patterns depending on the wire inter-site couplings. In some cases the structure of these beats provides useful information about the system parameters.