High Frequency Behavior of the Infrared Conductivity of Cuprates

TL;DR

This paper analyzes infrared conductivity data in cuprates, revealing that high-frequency behavior is due to electrons interacting with a broad spectrum of electronic bosons, not phonons, with implications for quantum criticality.

Contribution

It provides a detailed analysis linking high-frequency infrared conductivity in cuprates to electron-boson interactions with a broad spectrum, supporting an electronic origin of the bosons.

Findings

High-frequency conductivity follows a power-law behavior consistent with electron-boson interactions.

The boson spectrum has an upper cut-off around 300 meV.

Data supports electronic, not phononic, origin of the bosons.

Abstract

We analyze recent infrared conductivity data in the normal state of the cuprates. We find that the high frequency behavior, which has been suggested as evidence for quantum critical scaling, is generally characteristic of electrons interacting with a broad spectrum of bosons. From explicit calculations, we find a frequency exponent for the modulus of the conductivity, and a phase angle, in good agreement with experiment. The data indicate an upper cut-off of the boson spectrum of order 300 meV. This implies that the bosons are of electronic origin rather than phonons.