Anderson's “theorem” and Bogoliubov-de Gennes equations for surfaces and impurities
Abstract In order to incorporate spatial inhomogeneity due to nonmagetic impurities, Anderson [1] proposed a BCS-type theory in which single-particle states in such an inhomogeneous system are used. We examine Anderson's proposal, in comparison with the Bogoliubov-de Gennes equations, for the attractive Hubbard model on a system with surfaces and impurities.