Flux-quantization in one-dimensional copper-oxide models

(Received 19 October 1992, accepted 26 October 1992)

Abstract
A calculation of the ground state energy as a function of flux in a one-dimensional `copper-oxide model' on rings of finite circumference L, including on-site interactions, and a nearest neighbor interaction V, is presented. For V of the order of the charge-transfer gap or larger, the model extrapolated to large L exhibits flux-quantization with charge 2e. The extrapolated superfluid stiffness appears, however, finite only for not too large V. These results suggest a superconductive state at V of order the charge-transfer gap of the model, but a paired and phase-separated state at larger V.