Influence of the pair coherence on the charge tunneling through a quantum dot connected to a superconducting lead

Abstract

We analyze the charge transport through a single level quantum dot coupled to a normal (N) and superconducting (S) leads where the electron pairs exist either as the coherent (for temperatures below T_c) or incoherent objects (in a region T_c < T < T*). This situation can be achieved in practice if one uses the high T_c superconducting material where various precursor effects have been observed upon approaching $T_{c}$ from above. Without restricting to any particular microscopic mechanism we investigate some qualitative changes of the nonequilibrium charge current caused by the electron pair coherence.