Coherent twin boundaries in high-Tcsuperconducting oxides

Abstract
When subjected to a low-temperature annealing cycle similar to that of Bhargava et al., 1:2:3 superconducting oxides are shown to form fine, 250-Å spaced twins. The symmetry of the crystal is markedly altered. A theoretical calculation shows that twins introduce minigaps into the electronic structure. The implications for high-Tc superconductivity are discussed.