ARPES and optical renormalizations: phonons or spin fluctuations

TL;DR

This paper compares phonon and spin fluctuation mechanisms for superconductivity in cuprates, using ARPES and optical data, and finds spin fluctuations provide a more consistent explanation across different measurements.

Contribution

It evaluates the relative merits of phonon versus spin fluctuation mechanisms for superconductivity using combined ARPES and optical data, favoring spin fluctuations.

Findings

ARPEs data shows a structure around 80 meV linked to quasiparticle interactions.

Optical data analysis favors spin fluctuations as the more natural explanation.

Both mechanisms can explain ARPES data, but spin fluctuations better fit the combined data set.

Abstract

Improved resolution in both, energy and momentum in ARPES-data has lead to the establishment of a definite energy scale in the dressed quasiparticle dispersion relations. The observed structure around 80 meV has been taken as evidence for coupling to phonons and has re-focused the debate about the mechanism of superconductivity in the cuprates. Here we address the relative merits of phonon as opposed to spin fluctuation mechanisms. Both possibilities are consistent with ARPES. On the other hand, when considerations are extended to infrared optical data, a spin fluctuation mechanism provides a more natural interpretation of the combined sets of data in Bi_2Sr_2CaCu_2O_{8+\delta} (Bi2212).