## Abstract

We consider normal-state properties, the pairing instability temperature, and the structure of the pairing gap in electron-doped cuprates. We assume that the pairing is mediated by collective spin excitations, with antiferromagnetism emerging with the appearance of hot spots. We use a low-energy spin-fermion model and the Eliashberg theory up to two-loop order. We justify ignoring vertex corrections by extending the model to N1 fermionic flavors, with 1/N playing the role of a small Eliashberg parameter. We argue, however, that it is still necessary to solve coupled integral equations for the frequency-dependent fermionic and bosonic self-energies in both the normal and the superconducting states. Using the solution of the coupled equations, we find an onset of d-wave pairing at T_{c}∼30 K, roughly three times larger than the one obtained previously, where it was assumed that the equations for fermionic and bosonic self-energies decouple in the normal state. To obtain the momentum and frequency-dependent d-wave superconducting gap, Δ(k_{F}, ω_{n}), we derive and solve the nonlinear gap equation together with the modified equation for the bosonic self-energy which below T_{c} also depends on Δ(k-_{F},ω_{n}). We find that Δ(k_{F},ω_{n}) is a nonmonotonic function of momentum along the Fermi surface, with its node along the zone diagonal and its maximum some distance away from it. We obtain 2Δ_{max}(T→0)/ T_{c}~4. We argue that the value of T_{c}, the nonmonotonicity of the gap, and the 2Δ_{max}/T_{c} ratio are all in good agreement with the experimental data on electron-doped cuprates.

Original language | English (US) |
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Article number | 064518 |

Journal | Physical Review B - Condensed Matter and Materials Physics |

Volume | 83 |

Issue number | 6 |

DOIs | |

State | Published - Feb 11 2011 |

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