Theory of Raman scattering on electron-doped high-$T_c$ superconductor

TL;DR

This paper presents a theoretical analysis of Raman spectra in electron-doped cuprate superconductors using a two-band model, explaining experimental peak behaviors and supporting $d_{x^2-y^2}$-wave pairing symmetry.

Contribution

The study introduces a two-band model that accounts for Raman spectral features and doping evolution in electron-doped cuprates, highlighting the pairing symmetry and mechanism.

Findings

The $B_{2g}$ peak occurs at higher frequency than $B_{1g}$ at optimal doping.

The model explains doping-dependent changes in Raman peaks.

Superconducting pairing has $d_{x^2-y^2}$-wave symmetry.

Abstract

We have analyzed the $B_{1g}$ and $B_{2g}$ Raman spectra of electron-doped cuprate superconductors Nd$_{2-x}$Ce$_{x}$CuO$_4$ and Pr$_{2-x}$Ce$_{x}$CuO$_4$ using a weakly coupled two-band model. One of these two bands is centered around $(\pm \pi/2, \pm \pi/2)$ and couples more strongly with the $B_{2g}$ mode, while the other is centered around $(\pm \pi, 0)$ and $(0, \pm \pi)$ and couples more strongly with the $B_{1g}$ mode. This model explains in a natural way why the $B_{2g}$ Raman peak occurs at a higher frequency than the $B_{1g}$ one at optimal doping, and how these two peaks change with doping in agreement with experiments. Our result suggests that the superconducting pairing in electron-doped high-$T_c$ cuprates has the $d_{x^2-y^2}$-wave symmetry and results from the same mechanism as for hole doped materials.