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

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.

5 RevTeX4 pages, 3 EPS figures, replaced with published version (two tables added)