Influence of surface roughness on subdominant pairing in d-wave superconductors

We study a d-wave superconductor with dominant d(x2-y2)-wave order parameter and subdominant pairing in either the s- or the d(xy)-wave channel near a surface. In particular we analyze the influence of surface roughness on the mixed order parameter which may break the time-reversal symmetry. We find that the subdominant component is suppressed by the roughness independent of its pairing symmetry; for very rough surfaces the subdominant component may even vanish completely. Additionally we discuss a possible real-valued admixture which counteracts the suppression of the d(x2-y2)-wave order parameter at the surface. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.