Effect of normal-state pseudogap on physical quantities in Hubbard model for underdoped high-TC cuprates

Abstract

The authors develop the strong-coupling theory of coexisting charge-density-wave (CDW) and superconductivity d-wave gaps within the framework of the FLEX (fluctuation exchange) approximation for the two-dimensional Hubbard model. For nested sections of the Fermi surface these equations reduce to the previous FLEX equations for superconductivity where the squared energy gap {phi}{sub s}{sup 2} in the denominator of the Green`s function is replaced by ({phi}{sub 2}{sup 2} + {phi}{sub c}{sup 2}) (here {phi}{sub s} is the superconductivity and {phi}{sub c} the CDW gap). The authors solve these equations by taking for {phi}{sub c} a phenomenological d-wave gap. The resulting neutron scattering intensity, spin-lattice relaxation rate 1/T{sub 1}, Knight shift, resistivity, and photoemission intensity are in qualitative agreement with the data on underdoped high-{Tc} cuprates. The {Tc} for superconductivity decreases and the crossover temperature T{sub *} for 1/T{sub 1}T increases with increasing gap amplitude of {phi}{sub c} which is in qualitative agreement with the phase diagram for underdoped cuprates.