Theory of high-Tc superconductors within an Anderson lattice model

An Anderson lattice model for high-Tc superconductors, in particular La2-xSrxCuO4, is set up and explicitly transformed into a slave-boson representation. The model is solved using a formal 1N expansion technique, where N is the degeneracy of the d9 state, working to leading-N approximation in the normal state and O(1N) in the superconducting state. Normal-state properties such as susceptibility, density of states, and the location of added holes are calculated and compared with experiment. The model is an s-wave superconductor in the present approximation for realistic parameters. The gap-to-Tc ratio, specific-heat jump, and Hc(0) take their Bardeen-Cooper-Schrieffer values. The variation of Tc with doping is successfully explained. A calculation of the critical region, taking into account strong tetragonal anisotropy, finds its width of order 1 K, in agreement with experiment. © 1988 The American Physical Society.