Theory of Local Density of States of d-Wave Superconducting State Near   the Surfaces of the t-J Model
  Spatial dependencies of the pair potential and the local density of states near the surfaces of $d_{x^{2}-y^{2}}$-wave superconductors are studied theoretically. The calculation is based on the t-J model within a mean-field theory with Gutzwiller approximation. Various types of surface geometries are considered. Similar to our result in the extended Hubbard model, it is found that the formation of zero-energy states strongly depends on the surface geometry. In addition to this feature, the zero-energy states give peak splitting for the (110) surfaces when the super-exchange interaction $J$ is large. This is due to the induced s-wave component near the surface. The present result explains the microscopic origin of the spontaneous time- reversal symmetry breaking at the surfaces of high-$T_{c}$ superconductors. 
Y. Tanuma, Y. Tanaka (Niigata Univ.), M. Ogata (Tokyo Univ.), S.   Kashiwaya (ETL)