PUB - Publikationen an der Universität Bielefeld

We 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(s)(2) in the denominator of the Green's function is replaced by (phi(s)(2) + phi(c)(2)) (here phi(s) is the superconductivity and phi(c) the CDW gap). We solve these equations by taking for phi(c) a phenomenological d-wave gap. The resulting neutron scattering intensity, spin-lattice relaxation rate 1/T-1, Knight shift, resistivity, and photoemission intensity are in qualitative agreement with the data on underdoped high-T-c cuprates. The T-c for superconductivity decreases and the crossover temperature T* for 1/T1T increases with increasing gap amplitude of phi(c) which is in qualitative agreement with the phase diagram for underdoped cuprates.