Optical symmetries and anisotropic transport in high-Tc superconductors

TL;DR

This paper presents a symmetry-based analysis linking electronic Raman response to transport properties in high-Tc cuprates, revealing doping-independent nodal transport and quantum critical behavior near specific doping levels.

Contribution

It introduces generalized scaling relations between Raman response and conductivities, connecting symmetry analysis with experimental transport data in cuprates.

Findings

Nodal transport is doping independent and metallic.

Transport near BZ axes is influenced by a quantum critical point at p~0.22.

c-axis conductivity rise below Tc is due to partial momentum conservation.

Abstract

A simple symmetry analysis of in-plane and out-of-plane transport in a family of high temperature superconductors is presented. It is shown that generalized scaling relations exist between the low frequency electronic Raman response and the low frequency in-plane and out-of-plane conductivities in both the normal and superconducting states of the cuprates. Specifically, for both the normal and superconducting state, the temperature dependence of the low frequency $B_{1g}$ Raman slope scales with the $c-$axis conductivity, while the $B_{2g}$ Raman slope scales with the in-plane conductivity. Comparison with experiments in the normal state of Bi-2212 and Y-123 imply that the nodal transport is largely doping independent and metallic, while transport near the BZ axes is governed by a quantum critical point near doping $p\sim 0.22$ holes per CuO$_{2}$ plaquette. Important differences for La-214 are discussed. It is also shown that the $c-$ axis conductivity rise for $T\ll T_{c}$ is a consequence of partial conservation of in-plane momentum for out-of-plane transport.