Negative differential conductance and super-Poissonian shot noise in a single quantum dot coupled to two noncollinear polarized ferromagnetic leads

Abstract

We have theoretically studied the full counting statistics of electron transport through a single quantum dot (QD) weakly coupled to two noncollinearly polarized ferromagnetic leads. We found a strong robust bias-voltage-tunable negative differential conductance (NDC) region, in which the shot noise is dramatically enhanced and reaches up to a super-Poissonian value. In particular, the formed super-Poissonian shot noise can still occur in a wide bias voltage region where only the singly-occupied electronic states entering the bias voltage window. The underlying mechanisms of the observed NDC and super-Poissonian shot noise originate from the quantum coherence between the two singly-occupied electronic states. In addition, the skewness in the NDC regime can be significantly increased up to a large positive value, which is also attributed to the quantum coherence of the QD system, and the variation of the skewness value is more sensitive to the quantum coherence than the shot noise. Our findings suggest a QD-based tunable NDC device, and the predicted properties of high-order current cumulants can provide a deeper understanding of electron transport through the single QD.