GINZBURG-LANDAU EXPANSION AND THE SLOPE OF THE UPPER CRITICAL-FIELD IN DISORDERED SUPERCONDUCTORS WITH ANISOTROPIC PAIRING

It is demonstrated that the slope of the upper critical field \dH(c2)/ dT\(Tc) in superconductors with d-wave pairing drops rather fast with concentration of normal impurities, while in superconductors with anis otropic s-wave pairing \dH(c2)/dT\(Tc) grows, and in the limit of stro ng disorder is described by the known dependences of the theory of ''d irty'' superconductors. This allows to use the measurements of H-c2 in disordered superconductors to discriminate between these different ty pes of pairing in high-temperature superconductors.