Nonlocal transport mediated by nonlocal Hikami boxes: Condensation of evanescent quasiparticles injected into the superconducting gap

TL;DR

This paper investigates how evanescent quasiparticles in superconductors can induce nonlocal transport phenomena through nonlocal Hikami boxes, revealing a non-BCS out-of-equilibrium condensate supported by microscopic theory.

Contribution

It introduces a microscopic theory explaining nonlocal transport mediated by nonlocal Hikami boxes in superconductors, highlighting the role of evanescent quasiparticles and retarded interactions.

Findings

Evanescent quasiparticles can propagate over distances larger than the coherence length.

Nonlocal Hikami boxes facilitate nonlocal transport in superconductors.

The theory aligns with recent experimental observations.

Abstract

Evanescent quasiparticles entering a superconductor and propagating over distances larger than the coherence length give rise to intermediate states induced by double Andreev scattering on disorder.The resulting effective attractive interaction between evanescent quasiparticles is retarded at the extremely slow frequency of the applied bias voltage. The non-BCS out-of-equilibrium mesoscopic condensate is compatible with a recent experiment [S. Russo et al., Phys. Rev. Lett. 95, 027002 (2005)]. Microscopic theory is discussed in the random phase approximation.