DISORDER-INDUCED DECOUPLING OF PANCAKE VORTICES IN A LAYERED SUPERCONDUCTOR

We consider the effect of pancake vortices induced by a magnetic field on the Josephson coupling in a disordered, layered superconductor. Du e to the random displacements of vortices, the magnetic field suppress es the Josephson coupling. We find the characteristic value of the ''d ecoupling'' field. The effective Josephson energy does not drop to zer o above this field, but saturates at some small value and remains fiel d independent in the regime of individual pinning. Crossover to the co llective pinning regime at higher fields and temperatures leads to par tial restoration of the Josephson energy. We studied also the influenc e of the pancake wandering on the field distribution inside the superc onductor. We found that the feature which is most sensitive to the pan cake misalignment is the large field tail in the distribution function . We show that the asymmetry of the field distribution induced by this tail disappears at fields substantially smaller than the decoupling f ield.