Evolution of the neutron resonances in AFe2Se2

TL;DR

This paper investigates how neutron scattering resonances evolve with doping in AFe2Se2, revealing how magnetic susceptibility measurements can distinguish between competing superconducting gap symmetries.

Contribution

It provides a theoretical analysis of neutron scattering signatures for different superconducting states in AFe2Se2, aiding experimental identification of pairing symmetry.

Findings

D-wave state transitions to s± state with doping.

Near-degeneracy of d-wave and s± states over certain doping ranges.

Neutron scattering resonances can differentiate between pairing symmetries.

Abstract

Recent experiments on the alkali-intercalated iron selenides have raised questions about the symmetry of the superconducting phase. Random phase approximation calculations of the leading pairing eigenstate for a tight- binding 5-orbital Hubbard-Hund model of AFe2Se2 find that a d-wave (B1g) state evolves into an extended s{\pm} (A1g) state as the system is hole-doped. However, over a range of doping these two states are nearly degenerate. Here, we calculate the imaginary part of the magnetic spin susceptibility \chi"(q,{\omega}) for these gaps and discuss how the evolution of neutron scattering resonances can distinguish between them.