VORTEX CONTRIBUTION TO SPECIFIC-HEAT OF DIRTY D-WAVE SUPERCONDUCTORS - BREAKDOWN OF SCALING

We consider the problem of the vortex contribution to thermal properti es of dirty d-wave superconductors. In the clean limit, the main contr ibution to the density of states in a d-wave superconductor arises fro m extended quasiparticle states which may be treated semiclassically, giving rise to a specific heat contribution delta C(H) similar to H-1/ 2. We show that the extended states continue to dominate the dirty lim it, but lead to a H log H behavior at the lowest fields, H-c1 less tha n or similar to H much less than H-c2. This crossover may explain rece nt discrepancies in specific heat measurements at low temperatures and fields in the cuprate superconductors. We discuss the range of validi ty of recent predictions of scaling with H-1/2/T in real samples. (C) 1998 Elsevier Science Ltd.