Coherent current correlations in a double-dot Cooper pair splitter

Abstract

Exact analytical formulas are derived, by means of Keldysh Green functions, for currents and current correlation functions in a Cooper pair splitter modelled on a double quantum dot system coherently coupled to a superconductor and two normal metallic electrodes. Confining to the subspace with the inter-dot singlet we show perfect entanglement of split electrons in two separated crossed Andreev reflection processes. The studies are focused on the noise power spectrum in a whole bias voltage range. In particular, in the large voltage limit shot noise dominates and its spectrum exhibits two extraordinary side dips related to resonant inter-level current correlations caused by coherent electron-hole recombination processes accompanied by emission and absorption of photons. In the linear response limit we derived the frequency dependent admittance which shows different interference patterns for the cross and the auto current correlations.