Comment on: Nonmonotonic $d_{x^{2}-y^{2}}$ Superconducting Order Parameter in Nd$_{2-x}$Ce$_x$CuO$_4$

TL;DR

This paper critiques a recent claim that a non-monotonic $d_{x^2-y^2}$ superconducting gap explains Raman data in Nd$_{2-x}$Ce$_x$CuO$_4$, arguing the evidence is insufficient and inconsistent with other experiments.

Contribution

It provides a simple model calculation showing the previous interpretation is not supported by the data or other experimental results.

Findings

The proposed gap functional form is inconsistent with measured spectra.

The interpretation of a non-monotonic gap is not supported by additional experiments.

The issue of the superconducting gap in electron-doped cuprates remains unresolved.

Abstract

In a recent letter Blumberg and collaborators claim that a non-monotonic $d_{x^2-y^2}$ form for the superconducting order parameter is required to explain their Raman scattering measurements in Nd$_{2-x}$Ce$_x$CuO$_4$ . In this comment we show with a simple model calculation that the basis for this conclusion is insufficient. The proposed functional dependence of the gap is neither consistent with their measured spectra nor compatible with other experimental results. Therefore the issue of the superconduing gap in electron-doped systems cannot be considered solved by now.