Eur. Phys. J. B 43, 445-452 (2005)
https://doi.org/10.1140/epjb/e2005-00077-7

Structurally asymmetric d.c. SQUID's in the presence of coupling energy inhomogeneity of the junctions studied by means of the reduced two-junction interferometer model

INFM and DIIMA, Università degli Studi di Salerno 84084 Fisciano (SA), Italy

Corresponding author: ^a rdeluca@unisa.it

Received: 24 September 2004
Published online: 30 March 2005

Abstract

The effects of structural asymmetries and of inhomogeneities in the junction parameters on the electrodynamic response of conventional d.c. SQUID's are studied both analytically and numerically. By a first-order perturbative expansion with respect to the parameter β and to the deviation parameters describing structural asymmetry and inhomogeneity, we write the reduced dynamical equation for the average superconducting phase difference of a conventional d.c. SQUID. As in homogeneous and symmetric SQUID's, the resulting dynamical equation is seen to be similar to that of a single junction with an unconventional current-phase relation characterized by a second harmonic contribution; in addition, a cosine term appears as a consequence of superconducting coupling inhomogeneity. By means of the reduced dynamical equation, the I-V characteristics in the presence of an external rf field and the critical current of the device are studied in the absence of noise.