Abstract
The appropriate infinite-wavelength →0 and zero-frequency ω→0 limits of the paramagnetic current-current correlation function provide criteria for determining whether a system is insulating, metallic, or superconducting. Here we discuss these criteria for lattice models and present Monte Carlo data for the two-dimensional positive- and negative-U Hubbard models that imply that the ground state of the half-filled positive-U Hubbard model is an insulator, the doped state is a metal, and the negative-U Hubbard model is a superconductor.
- Received 16 November 1992
DOI:https://doi.org/10.1103/PhysRevB.47.7995
©1993 American Physical Society