Electronic and Cooper pair tunneling signatures in the electronic spectra of superconductors coupled to quantum dot nano-junction

Abstract

We present here calculations on electronic spectra of a system consisting of a quantum dot connected to superconducting leads on its either side. In these calculations the generated spectra has contributions from both, the single particle tunneling, and from the tunneling Cooper pair of electrons. In this, the Anderson model is used for the theoretical construct, and hence, the single particle tunneling, the Josephson tunneling, the energy states of the quantum dot and the super conducting order parameter for BCS superconductors are principally considered. The Green's function equation of motion technique is used to obtain the single particle spectral function. Our results from the numerical computations in the present work indicate, under certain conditions, the occurrence of breaking of Cooper pairs at the junctions between the superconducting leads and the quantum dot. These are seen to be, understandably, depending on the interaction terms included in our model. Our present work suggests a way to understand the interplay of single particle and the ‘Cooper pairs tunneling’ in the resultant electronic spectra in the light of extended Anderson model applicable to the system. It thus presents a theoretical understanding on the transmission of supercurrents through nanoscopic junctions, such as that considered here.