QUASI-CLASSICAL THEORY OF TWIN BOUNDARIES IN HIGH-T-C SUPERCONDUCTORS

We investigate the electronic structure of twin boundaries in orthorho mbically distorted high-T-c, materials using the quasiclassical theory of superconductivity. At low temperatures we find a local instability to a time-reversal symmetry breaking state at the twin boundary. This state yields spontaneous currents along the twin boundary that are mi croscopically explained by the structure of the quasiparticle bound st ates. We calculate the local density of states and find a splitting in the zero-bias peak once the spontaneous currents set in. This splitti ng is measurable by STM techniques and is a unique signature of time-r eversal breaking states at a twin boundary.