Coherent transport in Josephson-Junction rhombi chain with quenched disorder

Abstract

We consider a chain of Josephson-junction rhombi (proposed originally by Doucot and Vidal) in quantum regime. In a regular chain with no disorder in the maximally frustrated case when magnetic flux through each rhombi Φ_r is equal to one half of superconductive flux quantum Φ_0, Josephson current is due to correlated transport of pairs of Cooper pairs, i.e. charge is quantized in units of $4e$. Sufficiently strong deviation δΦ=|Φ_r-Φ_0/2| > δΦ^c from the maximally frustrated point brings the system back to usual $2e$-quantized supercurrent. For a regular chain δΦ^c was calculated by us previously. Here we present detailed analysis of the effect of quenched disorder (random stray charges and random fluxes piercing rhombi) on the pairing effect.

21 pages, 5 figures