Theory of optical conductivity in detwinned YBa$_2$Cu$_3$O$_{y}$

TL;DR

This paper presents a theoretical study of the optical conductivity in detwinned YBa2Cu3O7−y, revealing a superconductor-insulator transition driven by plane-chain coupling and antiferromagnetic order, and explaining recent experimental observations.

Contribution

It introduces a theoretical model explaining the superconductor-insulator transition and the emergence of a low-frequency peak in optical spectra due to plane-chain coupling.

Findings

Chain is superconducting for y>6.67 and insulating for y<6.67.

A new low-frequency peak appears in the in-plane spectra in the superconducting state.

The model accounts for recent experimental results.

Abstract

We study theoretically the chain and in-plane optical conductivities of detwinned YBa$_2$Cu$_3$O$_{y}$. We elaborate that the chain is superconducting for $y>6.67$ while insulating for $y<6.67$ due to the competition between the plane-chain coupling and the antiferromagnetic order, corresponding to a superconductor-insulator transition. Stemming also from the coupling between the plane and chain, a new peak emerges at a low frequency in the in-plane spectra in the superconducting state, while it disappears in the normal state. Our scenario accounts satisfactorily for very recent experiments.