Operator projection theory for electron differentiation in underdoped cuprate superconductors

Metals approaching the Mott insulator generate a new hierarchy in the electronic structure accompanied by an electron differentiation with emergence of strongly momentum dependent structure, beyond the Mott-Hubbard, Brinkman-Rice and Slater pictures of the Mott transition. To consider such nonlinear phenomenon, we develop an analytic nonperturbative theory based on operator projections combined with a self-consistent treatment of the low-energy excitations. This reproduces the Hubbard bands, Mott gap, spin fluctuations, mass divergence, diverging charge compressibility, and strongly renormalized flat and damped dispersion similar to angle-resolved photoemission data in high-T(c) cuprates. Electronic spectra show a remarkable similarity to numerical results. (C) 2002 Elsevier Science Ltd. All rights reserved.