Tunneling density of states in d-wave superconductors with rough surfaces

We discuss the novel surface states which may occur near a boundary in a d-wave superconductor and how these states are affected by surface diffusivity. The surface roughness is taken into account via the ''Randomly Rippled Wall Model'', and all calculations ate performed within the quasiclassical theory of superconductivity. We consider a uniaxial system with a bulk order parameter of d(x2-y2) symmetry. Our analysis focuses on the emergence of surface states of a symmetry other than that of the stable bulk phase when more than one attractive symmetry channel is present. The conditions for the stability of the various surface states and their impact on the tunneling characteristics are discussed.