Superfluid Weight, Free Carrier Density, and Specific Heat of the d=3 tJ Model at Finite Temperatures

TL;DR

This study uses renormalization-group theory to analyze the superfluid weight, free carrier density, and specific heat in the three-dimensional tJ model, revealing optimal doping levels and phase characteristics relevant to high-temperature superconductivity.

Contribution

It provides a detailed theoretical analysis of the tJ model at finite temperatures, identifying the tau phase and its properties related to superfluidity and carrier behavior.

Findings

Optimal hole doping occurs at n_i ≈ 0.63-0.68.

Superfluid weight peaks in the tau phase and drops sharply in overdoped regions.

Free carrier density increases with doping up to optimal levels and then saturates.

Abstract

The superfluid weight, free carrier density, and specific heat of the three-dimensional tJ model are calculated by renormalization-group theory. We find that optimal hole doping for superfluidity occurs in the electron density range of n_i approximately between 0.63 - 0.68, where the superfluid weight n_s/m* reaches a local maximum. This density range is within the novel tau phase, where the electron hopping strength renormalizes to infinity, the system remains partially filled at all length scales, and the electron-hopping expectation value remains distinctively non-zero at all length scales. The calculated superfluid weight drops off sharply in the overdoped region. Under hole doping, the calculated density of free carriers increases until optimal doping and remains approximately constant in the overdoped region, as seen experimentally in high-T_c materials. Furthermore, from calculation of the specific heat coefficient gamma, we see clear evidence of a gap in the excitation spectrum for the tau phase.