In this paper we calculate the ground state phase diagram of a Josephson
Junction ladder when screening field effects are taken into account. We study
the ground state configuration as a function of the external field, the
penetration depth and the anisotropy of the ladder, using different
approximations to the calculation of the induced fields. A series of tongues,
characterized by the vortex density ω, is obtained. The vortex density
of the ground state, as a function of the external field, is a Devil's
staircase, with a plateau for every rational value of ω. The width of
each of these steps depends strongly on the approximation made when calculating
the inductance effect: if the self-inductance matrix is considered, the
ω=0 phase tends to occupy all the diagram as the penetration depth
decreases. If, instead, the whole inductance matrix is considered, the width of
any step tends to a non-zero value in the limit of very low penetration depth.
We have also analyzed the stability of some simple metastable phases: screening
fields are shown to enlarge their stability range.Comment: 16 pp, RevTex. Figures available upon request at
[email protected] To be published in Physical Review B (01-Dec-96