SURFACE-STATES IN D-WAVE SUPERCONDUCTORS

On the basis of a two-dimensional tight-binding model, the eigenstates of quasiparticles in a d-wave superconductor with a{110} surface at t he ground state, T = 0 K, are investigated through self-consistently s olving the Bogoliubov-de Gennes equation. The order parameter is consi derably suppressed near the surface. The existence of bound surface st ates critically depends on a parameter k(y) (the parallel component of the wave number vector to the surface). Besides the midgap states whi ch exist in regions 0 < \k(y)\ < k(m) and pi - k(m) < \k(y)\ < pi, it is found that k(y) with \k(y)\ < k(n) or \pi - k(n)\ < \k(y)\, there c an also appear a number of surface states with nonzero energies. The p arameters k(m) and k(n) are close to the Fermi wave number k(0) in the y direction, and k(n) < k(m) < k(0).