Coherent transport in Josephson-junction rhombi chain with quenched disorder

Ivan V. Protopopov; Mikhail V. Feigel’man

doi:10.1103/PhysRevB.74.064516

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Coherent transport in Josephson-junction rhombi chain with quenched disorder

Ivan V. Protopopov, Mikhail V. Feigel’man

DOI 10.1103/PhysRevB.74.064516 · Physical Review B

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Abstract

We consider a chain of Josephson-junction rhombi (proposed originally by Douçot and Vidal) in the quantum regime. In the maximally frustrated case when magnetic flux through each rhombi Φr is equal to one-half of the superconductive flux quantum Φ0, the Josephson current is due to the correlated transport of pairs of Cooper pairs; i.e., charge is quantized in units of 4e. A sufficiently strong deviation δΦ≡∣Φr−Φ0∕2∣>δΦc from the maximally frustrated point brings the system back to the usual 2e-quantized supercurrent. For a regular chain δΦc was calculated by us in Phys. Rev. B 70, 184519 (2004). Here we present a detailed analysis of the effect of quenched disorder (random stray charges and random fluxes piercing rhombi) on the pairing effect. For the case of a chain with random stray charges in the quantum regime we derive the probability to find the system in the 4e-dominated regime and estimate the characteristic value of the critical deflection δΦc.