Tunnelling of entangled Kondo singlet in two-reservoir nanocontact systems under bias

Abstract

Tunnelling conductances observed for mesoscopic Kondo systems exhibit a zero-bias peak and two coherent side peaks. The former peak is usually understood as a Kondo effect and the latter side peak is recently clarified as the effect of inter-reservoir coherence. However, fitting the experimental $dI/dV$ line shapes, where $I$ and $V$ denote the current and bias voltage, respectively, has not been performed theoretically. Here, we fit the entire line shape range of the tunnelling conductance observed for a quantum dot, quantum point contact, and magnetized atom adsorbed on an insulating layer covering a metallic substrate by studying the tunnelling of entangled Kondo singlet (EKS) formed in a two-reservoir mesoscopic Kondo system. We also clarify the characteristic dynamics forming each coherent peak in terms of the processes comprising spin exchange, singlet hopping, and singlet partner changing. Tunnelling of entangled Kondo singlet can be applied to understanding the tunnelling conductance observed for a sample with strong electron correlation.