Recently a number of experiments have investigated a mesoscopic system in which a very inhomogeneous magnetic field distribution is generated at a two-dimensional electron gas by depositing a type-II superconducting film on top. The weak-localization magnetoconductivity in such structures has been shown to be qualitatively different from the homogeneous magnetic field case and in complementary experiments it has been demonstrated that micrometer-sized devices of this type can be sensitive to the dynamics of individual quanta of flux. The huge latent potential of such structures will only be realized if quantitative models of the detector operation can be developed. In this Brief Report we demonstrate that available asymptotic results for the magnetoconductivity [Phys. Rev. B 36, 3135 (1987)] are of limited use in describing real experiments, but show that quantitative agreement can be reached with a numerical model that has been developed here.

• Received 12 May 1992

DOI:https://doi.org/10.1103/PhysRevB.46.14912