Improved superconducting quantum interference devices by resistance asymmetry

Direct current superconducting quantum interference devices made by Josephs on junctions with asymmetric shunt resistances have been numerically invest igated in the low temperature regime. When combined with a damping resistan ce, the asymmetry leads to a flux to voltage transfer coefficient several t imes larger than the one typical of symmetric devices, together with a lowe r magnetic flux noise. These results show that this type of asymmetric devi ce may replace the standard ones in a large number of magnetometric applica tions, improving the sensitivity performance. The large transfer coefficien t may also simplify the readout electronics allowing a direct coupling of a symmetric devices to an external preamplifier, without the need of an imped ance matching flux transformer. (C) 2001 American Institute of Physics.