Reply to "Sharp-mode coupling in High-Tc Superconductors"

TL;DR

This paper compares optical and ARPES techniques in high-Tc superconductors, revealing that a sharp mode diminishes with doping and is likely not essential for high-temperature superconductivity.

Contribution

It demonstrates that optical self-energies can accurately track ARPES self-energies and shows the doping dependence of the sharp mode in superconductors.

Findings

Sharp mode intensity decreases with doping

Sharp mode disappears at doping level 0.23

Superconductivity remains strong despite mode disappearance

Abstract

Our optical technique has the advantage of being a bulk probe, which is less subject to uncertainties in the doping level and in the quality of the surface than angle resolved photoemission (ARPES). It is also capable of higher energy resolution and the overall noise level is lower. The disadvantage is that it gives momentum averaged properties. In light of these differences, it came as a surprise to us that our reported optical self-energies were able to track in accurate detail the ARPES self-energies of Johnson et al. Our data indicate that, as a function of doping, not only could both optical and ARPES techniques resolve the sharp mode from the background but also that the sharp mode intensity decreases uniformly, disappearing completely at a doping level of 0.23. As superconductivity is still strong at this doping level, with a Tc of 55 K, we conclude that the sharp mode was not an important contributor to high-temperature superconductivity.