Andreev Bound States Formation and Quasiparticle Trapping in Quench Dynamics Revealed by Time-Dependent Counting Statistics

We analyze the quantum quench dynamics in the formation of a phase-biased superconducting nanojunction. We find that in the absence of an external relaxation mechanism and for very general conditions the system gets trapped in a metastable state, corresponding to a non-equilibrium population of the Andreev bound states. The use of the time-dependent Full Counting Statistics (FCS) analysis allows us to extract information on the asymptotic population of even and odd manybody states, demonstrating that a universal behavior, dependent only on the Andreev states energy, is reached in the quantum point contact limit. These results shed light on recent experimental observations on quasiparticle trapping in superconducting atomic contacts.