Andreev bound states in high-Tc superconducting junctions

The formation of midgap states is a robust feature of d-wave superconductivity and provides a unified framework for many important effects which is reviewed: large Josephson current, low-temperature anomaly of the critical Josephson current, pi-junction behavior, zero-bias conductance peaks, paramagnetic currents, time reversal symmetry breaking, spontaneous interface currents, and resonance features in subgap currents. Taken together these effects, when observed in experiments, provide proof for d-wave superconductivity in the cuprates. 45 refs.