Spin-resolved impurity resonance states in electron-doped cuprate superconductors

With the aim at understanding the non-monotonic $d_{x^{2}-y^{2}}$-wave gap, we analyze the local electronic structure near impurities in the electron-doped cuprate superconductors. We find that the local density of states near a non-magnetic impurity in the scenario of $d_{x^{2}-y^{2}}$-wave superconductivity with higher harmonics is qualitatively different from that obtained from the $d_{x^{2}-y^{2}}$-wave superconductivity coexisting with antiferromagnetic spin density wave order. We propose that spin-polarized scanning tunneling microscopy measurements can distinguish the two scenarios and shed light on the real physical origin of a non-monotonic $d_{x^{2}-y^{2}}$-wave gap.