Edge-type Josephson junctions in narrow thin-film strips

We study the field dependence of the maximum current I(m)(H) in narrow edge-type thin-film Josephson junctions. We calculate I(m)(H) within nonlocal Josephson electrodynamics taking into account the stray fields. These fields affect the difference of phases of the order parameter across the junction and therefore the tunneling currents. We find that the phase difference along the junction is proportional to the applied field, depends on the junction geometry, but is independent of the Josephson critical current density, i.e., it is universal. An explicit formula for this universal function is derived and used to calculate I(m)(H). It is shown that the maxima of I(m)(H)proportional to 1 root H and the zeros of I(m)(H) are equidistant only in high fields. We find that the spacing between the zeros is proportional to 1/w(2), where w is the width of the junction. The general approach is applied to calculate I(m)(H) for a superconducting quantum interference device (SQUID) with two narrow edge-type junctions.