Time-dependent DMRG study on quantum dot under a finite bias voltage

Resonant tunneling through quantum dot under a finite bias voltage at zero temperature is investigated by using the adaptive time-dependent density matrix renormalization group (TdDMRG) method. Quantum dot is modeled by the Anderson Hamiltonian with the one-dimensional nearest-neighbor tight-binding leads. Initially the (,round state wave function is calculated with the usual DMRG method. Then the time evolution of the wave function Clue to the slowly changing bias voltage between the two leads is calculated by using the TdDMRG technique. Even though the system size is finite, the expectation values of current operator show steady-like behavior for a finite time interval, in which the system is expected to resemble the real nonequilibrium steady state of the infinitely long system. We show that front the time intervals one can obtain quantitatively correct results for differential conductance in a wide range of bias voltaic. Finally we observe an anomalous behavior in the expectation value of the double occupation operator at the dot < n(up arrow) n(down arrow)> as a function of bias voltage.