Probing the exciton condensate via shot noise spectroscopy in superconducting hybrid structures based on excitonic insulators

We theoretically study the shot noise and the Fano factor in a voltage-biased junction consisting of a bilayer excitonic insulator (EI) sandwiched between a bilayer semimetal (SM) and a conventional superconductor (S). By comparing the scenarios in SM-EI-S junctions with and without exciton condensates, we illustrate the effects of exciton condensates on the shot noise and demonstrate that the shot noise spectroscopy can signify the existence of exciton condensate in both well-contacted and tunnel SM-EI-S junctions. We also show that in a tunnel SM-EI-S junction, the Fano factor located in the super-Poissonian regime is a consequence of the competition between the exciton-mediated normal reflection and the Cooper-pair-mediated Andreev reflection. By virtue of the scattering probabilities, we elucidate the underlying physics. These results offer an alternative route toward the identification of neutral exciton condensate via charge transport measurements.