LOWER CRITICAL-FIELD OF A JOSEPHSON-COUPLED LAYER MODEL OF HIGH-TC SUPERCONDUCTORS

We calculate the lower critical field H(c1) for a magnetic field applied parallel to the layers of a Josephson-coupled layer model of high-T(c) superconductors. This result is obtained by using an expression for the vortex line energy that explicitly involves the gauge-invariant phase difference between superconducting layers. We examine the behavior of H(c1) as a function of temperature and discuss the manifestation of the superconductor discreteness below a crossover temperature where the coherence length zeta-c(T) becomes comparable to the lattice constant c. This temperature dependence is contrasted with the standard result for H(c1) for a continuous anisotropic type-II superconductor.