Nonmonotonic $d_{x^2-y^2}$ superconducting gap in electron-doped Pr$_{0.89}$LaCe$_{0.11}$CuO$_4$: Evidence of coexisting antiferromagnetism and superconductivity?

TL;DR

This paper models the nonmonotonic d-wave superconducting gap in electron-doped Pr$_{0.89}$LaCe$_{0.11}$CuO$_4$, showing coexistence of antiferromagnetism and superconductivity through a two-band framework with a third harmonic contribution.

Contribution

It introduces a theoretical model incorporating a third harmonic and quasiparticle broadening to explain experimental observations of the superconducting gap and coexistence of AFM and SC in the material.

Findings

The model reproduces the maximum in the superconducting gap near hot-spots.

The material behaves like a two-band superconductor with interband pairing.

AFM and SC orders coexist uniformly in the phase.

Abstract

Recent experiments on Pr$_{0.89}$LaCe$_{0.11}$CuO$_4$ observe an anisotropic spin-correlation gap and a nonmonotonic superconducting (SC) gap, which we analyze within the framework of a $t-t^{\prime}-t^{\prime\prime}-t^{\prime\prime\prime}-t^{iv}-U$ model with a $d_{x^2-y^2}$ pairing interaction including a third harmonic contribution. By introducing a realistic broadening of the quasiparticle spectrum to reflect small-angle scattering, our computations explain the experimental observations, especially the presence of a maximum in the leading edge gap in the vicinity of the hot-spots. Our analysis suggests that the material behaves like a {\it two-band} superconductor with the d-wave third harmonic acting as the {\it interband pairing gap}, and that the anti-ferromagnetic (AFM) and SC orders co-exist in a uniform phase.