Electromagnetic response of high-Tc superconductors -- the slave-boson and doped-carrier theories

TL;DR

This paper compares slave-boson and doped-carrier theories for high-Tc superconductors, analyzing doping effects on quasiparticle current and superfluid density, and predicts experimental signatures to distinguish these theories.

Contribution

It provides a detailed doping-dependent analysis of quasiparticle current and superfluid density in two slave-particle theories, highlighting differences and experimental signatures.

Findings

In slave-boson theory, the quasiparticle current renormalization factor $oldsymbol{eta}$ weakly depends on doping.

Doped-carrier theory aligns better with experimental data and explains hole-electron asymmetry.

Predicted STM signature of local staggered spin correlations in underdoped high-Tc compounds.

Abstract

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 $\alpha$ vanishes proportionally to the zero temperature superfluid density $\rho_S(0)$; however, we find that away from the $\rho_S(0) \to 0$ 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 STM measurements of underdoped high-Tc compounds. This experimental signature distinguishes the doped-carrier theory from other candidate mean-field theories of high-Tc superconductors, like the slave-boson theory and the conventional BCS theory.