Shot Noise In Quantum Transport Through Double Quantum Dots

The quantum dot system has attracted the widespread attention in the physics, chemistry, biology, materials and the cross area due to the especial structure and the wide application. Firstly, this paper introduces the structure, characteristics and application of quantum dots (QD). Secondly, quantum master equation and full counting statistics are described. Finally, based on the quantum master equation of particle numbers, we study full counting statistics of the electronic transport through metal electrode-QD-ferromagnetic electrode (N-D-F), ferromagnetic electrode-QD-metal electrode (F-D-N) and ferromagnetic electrode-QD-ferromagnetic electrode (F-D-F), discuss the effect of the spin exchange effect in quantum dots and the electrode polarization on the average current and shot noise. We have analyzed the contribution of the spin singlet and triplet states on the average current and shot noise, and has explained the super-Poissonian behavior of the shot noise in term of bunching effect induced by spin blockade.The main conclusion include:(1) the F-D-N system, for spin coupling ]= 0, the polarization of source electrode pL does not affect the current and shot noise. For J=-1Γ, the current and shot noise do not change basically. For J= 1Γ, with pL increasing, the current decreases while shot noise increases when only singlet state participates in the transport; the case is the opposite when only triplet state participates in the transport. (2) the N-D-F system, for three cases of J= 0, ± 1Γ, whether the transport through a singly-occupied state or the transport through a doubly-occupied state, with PR increasing, the current decreases while the shot noise increases and even achieves super Poisson distribution. (3) the F-D-F (parallel) system, whether the transport through a singly-occupied state or the transport through a doubly-occupied state, for three cases of J= 0、± 1Γ, the current does not change with p, but the shot noise increases with the increase of p and can reaches super Poisson distribution. (4) the F-D-F(antiparallel) system, for three cases of J=0、 1Γ, with p increasing the current decreases and the shot noise increases; When the singlet state participates in transport, the shot noise even can reach super Poisson distribution. The increase of the shot noise and the formation of super Poisson noise can be explained in term of bunching effect induced by spin blockade.