Non−Φ0−periodic macroscopic quantum interference in one-dimensional parallel Josephson junction arrays with unconventional grating structure

Abstract

A theoretical study is presented for a number N of Josephson junctions connected as a one-dimensional (1D) parallel array in such a manner that there are N−1 individual superconducting loops with arbitrary shape formed. In the resistive array mode, for bias currents I>Ic, all Josephson junctions in the array oscillate at the same magnetic field dependent frequency νB which is, in general, not a Φ0−periodic function of the strength of magnetic field B. Within the range of validity of the resistively and capacitively shunted junction (RCSJ) model the periodicity of νB is controlled by the array geometry alone and does not depend on the distribution of the array junction parameters. In the overdamped junction regime, νB is for certain types of unconventional grating structures a unique function around a sharp global minimum at B=0. This filter property does not apply for regular gratings and superconducting quantum interference devices (SQUID’s). Computer simulations of the full nonlinear array dynamics reveal that the qualitative macroscopic quantum interference properties of unconventional arrays are governed, irrespective of the strength of inductive couplings, by a complex structure factor SN(B) which can be determined analytically. Also, the performance of magnetometers based on 1D arrays with unconventional grating structure can be significantly better than the performance of conventional SQUID’s. In particular, 1D arrays with unconventional grating structure should provide a technically rather unsophisticated precision measurement of absolute strength and orientation of external magnetic fields.

Similar papers