d-Wave Bose-Einstein condensation and the London penetration depth in superconducting cuprates

As has been recently established, bipolaron formation leads to a d-wave Bos e-Einstein condensate in cuprates owing to the bipolaron (center-of-mass) e nergy dispersion rather than to a particular pairing interaction. We show t hat the unusual low-temperature-dependence of the magnetic field penetratio n depth lambda(T) in cuprates can be explained within the bipolaron scenari o as well. Both linear positive and negative slopes of lambda(T) occur depe nding on the random field profile and amount of disorder. (C) 1999 Elsevier Science B.V. All rights reserved.