Electromagnetic response of high-Tc superconductors:: Slave-boson and doped-carrier theories

We evaluate the doping dependence of the quasiparticle current and low-temperature superfluid density in two slave-particle theories of the tt(')t(')J model-the slave-boson theory and doped-carrier theory. In the slave-boson theory, the nodal quasiparticle current renormalization factor alpha proportionally vanishes to the zero temperature superfluid density rho(S)(0); however, we find that away from the rho(S)(0)-->0 limit, alpha displays a much weaker doping dependence than rho(S)(0). A similar conclusion applies to the doped-carrier theory, which differentiates the nodal and antinodal regions of momentum space. Due to its momentum space anisotropy, the doped-carrier theory enhances the value of alpha in the hole doped regime, bringing it to quantitative agreement with experiments, and reproduces the asymmetry between hole and electron doped cuprate superconductors. Finally, we use the doped-carrier theory to predict a specific experimental signature of local staggered spin correlations in doped Mott insulator superconductors, which, we propose, should be observed in scanning tunneling microscopy measurements of underdoped high-T-c compounds. This experimental signature distinguishes the doped-carrier theory from other candidate mean-field theories of high-T-c superconductors, such as the slave-boson theory and the conventional BCS theory.