Spectral and magnetic properties of the two-dimensional t–J model in the quantum disordered regime

Abstract

We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the two-dimensional (2D) t–J model in the paramagnetic state. A set of self-energy equations for hole and magnon Green's functions is solved numerically in the self-consistent Born approximation. The constraint can be fulfilled in the ranges of hole concentrations 0.02×0.17 and temperatures T=100 K. In this region, the hole spectrum is nonmetallic which is manifested in the variation with x of the quasiparticle weights of states and in the violation of Luttinger's theorem. With decreasing x from x≈0.17 hidden parts appear in the hole Fermi surface which can be interpreted as the opening of a pseudogap near (±π,0), (0,±π). Obtained size, symmetry and concentration dependence of the pseudogap are in agreement with photoemission data in Bi2212. Calculated temperature dependencies of the spin correlation length, spin-lattice relaxation times at the Cu and O sites, and static susceptibility are typical for the quantum disordered regime with a pseudogap in the spectrum of magnetic excitations. These quantities are in qualitative and in some cases in quantitative agreement with experiment in underdoped YBa2Cu3O6+δ. At x=0.12, the considered nonmetallic phase borders the phase of conventional metal.