Voltage-flux-characteristics of asymmetric dc SQUIDs

We present a detailed analysis of voltage-flux V(phi)-characteristics for a symmetric dc SQUIDs with various kinds of asymmetries. For finite asymmetry or in the critical currents of the two Josephson junctions, the minima in the V(phi)-characteristics for bias currents of opposite polarity are shift ed along the flux axis by Delta phi = alpha (1)beta (L), relative to each o ther; pr. is the screening parameter. This simple relation allows the deter mination of or in our experiments on YBa2Cu3O7-delta dc SQUIDs and comparis on with theory. Extensive numerical simulations within a wide range of pr a nd noise parameter Gamma reveal a systematic dependence of the transfer fun ction V-phi on alpha (1) and alpha (R) (junction resistance asymmetry). As for the symmetric de SQUID, V phi factorizes into g(Gamma beta (L)) f(alpha (1),beta (L)), where now f also depends on alpha (1). For beta (L)less tha n or similar to5 we find mostly a decrease of V-phi with increasing alpha ( 1), which however can only partially account for the frequently observed di screpancy in V-phi between theory and experiment for high-Tc dc SQUIDs.