Revival of Single-Particle Transport Theory for the Normal State of High-Tc Superconductors: II. Vertex Correction

TL;DR

This paper revisits single-particle transport theory for high-Tc superconductors' normal state, emphasizing vertex corrections within Fermi-liquid theory, and critiques the FLEX approximation's failure to satisfy Ward identities.

Contribution

It clarifies the role of vertex corrections in transport theory and highlights limitations of the FLEX approximation in high-Tc superconductor models.

Findings

Vertex correction does not change qualitative transport behavior.

FLEX approximation fails to satisfy Ward identity for fluctuation modes.

Relaxation-time approximation remains valid for normal state transport analysis.

Abstract

The vertex correction for the electric current is discussed on the basis of the Fermi-liquid theory. It does not alter the qualitative description of the electric transport by the relaxation-time approximation in the case of the normal state of high-Tc superconductors. The failure of the transport theory employing the fluctuation-exchange (FLEX) approximation is pointed out. It becomes manifest by considering the Ward identity for the fluctuation mode.