Dynamic transport characteristics of side-coupled double-quantum-impurity systems

Abstract

A systematic study is performed on time-dependent dynamic transport characteristics of a side-coupled double-quantum-impurity system based on the hierarchical equations of motion. It is found that the transport current behaves like a single quantum dot when the coupling strength is low during tunneling or Coulomb coupling. For the case of only tunneling transition, the dynamic current oscillates due to the temporal coherence of the electron tunneling device. The oscillation frequency of the transport current is related to the step voltage applied by the lead, while temperature T, electron–electron interaction U and the bandwidth W have little influence. The amplitude of the current oscillation exists in positive correlation with W and negative correlation with U. With the increase in coupling t 12 between impurities, the ground state of the system changes from a Kondo singlet of one impurity to a spin singlet of two impurities. Moreover, lowering the temperature could promote the Kondo effect to intensify the oscillation of the dynamic current. When only the Coulomb transition is coupled, it is found that the two split-off Hubbard peaks move upward and have different interference effects on the Kondo peak at the Fermi surface with the increase in U 12, from the dynamics point of view.

Finite‐Frequency Noise and Dynamical Charge Susceptibility in Single and Double Quantum Dot Systems

“…One assumes that the hopping integral V i𝛼 between the states |in⟩ in the dot i and |𝛼k⟩ in the reservoir 𝛼 does not depend on momentum k or index n. By using the Hamiltonian of Equation ( 1), one can model several geometries for the quantum dot system, such as left-connected or double-connected SQD, and serial-coupled, parallel-coupled, or side-coupled DQD, as depicted in Figure 1, the study of the latter geometry being in expansion. [30][31][32] To do this, we simply play with the values taken by the dot-reservoir coupling Γ 𝛼,ij and the dot-dot coupling  12 , as summarized in Table 1. These quantum dot systems are driven in an out-of-equilibrium situation under the application of a bias voltage defined as V = 𝜇 L − 𝜇 R , where 𝜇 L and 𝜇 R are the chemical potentials of the left and right reservoirs.…”