MIDGAP SURFACE-STATES AS A NOVEL SIGNATURE FOR D(X(A)(2)-X(B)(2))-WAVE SUPERCONDUCTIVITY

It is shown that a sizable areal density of midgap states exists on a {110} surface of a d(x)a2-x(b)2-wave superconductor, which can either have vacuum or an insulator at the surface, or be separated from vacuu m or an insulator by a clean, size-quantized, normal metal overlayer. These ''midgap'' states have many observable consequences-some of whic h axe briefly discussed here-which can be used as a clear signature to distinguish between d-wave and anisotropic s-wave superconductors.