Antiferromagnetic fluctuations, symmetry and shape of the gap function in the electron-doped superconductors: the functional renormalization-group analysis

TL;DR

This study uses the functional renormalization-group approach to analyze the symmetry and shape of the superconducting gap function in electron-doped superconductors, revealing non-monotonic behavior and dominant singlet pairing.

Contribution

It introduces a combined RG and Bethe-Salpeter method to determine the momentum dependence of the gap function in these materials, highlighting the non-monotonic gap and weak triplet instability.

Findings

Gap maxima at hot-spots or Brillouin zone diagonals.

Non-monotonic gap near (pi,0) and (0,pi) points.

Weak triplet f-wave like instability.

Abstract

The problem of the symmetry of the superconducting pairing and the form of the gap function in the electron-doped superconductors is reconsidered within the temperature-cutoff functional renormalization group approach combined with the Bethe-Salpeter equations. The momentum dependence of the order parameter for antiferromagnetic and superconducting instabilities in these compounds is analyzed. The gap function in the antiferromagnetic (particle-hole) channel has its maxima at the hot-spots, or at the diagonal of the Brilloin zone in their absence. The wavefunction in the singlet superconducting channel is non-monotonic in the vicinity of the (pi,0) and (0,pi) points, in striking similarity with recent experimental data. An instability in the triplet superconducting channel is much weaker than the singlet one and has an f-wave like form of the gap function.