(PI,0) antiferromagnetic spin excitations in superconducting Rb0.82Fe1.68Se2

TL;DR

This study uses inelastic neutron scattering to reveal antiferromagnetic spin excitations in superconducting Rb0.82Fe1.68Se2, showing similarities to iron arsenide and copper oxide superconductors, and suggesting a localized moment origin.

Contribution

It demonstrates the presence of AF spin excitations at (PI, 0) in Rb0.82Fe1.68Se2 and links these to localized moments, expanding understanding of magnetic excitations in iron-based superconductors.

Findings

AF spin excitations near (PI, 0) similar to iron arsenide superconductors

Excitations transition from incommensurate to commensurate with energy

Excitations originate from localized moments, not Fermi surface features

Abstract

We use inelastic neutron scattering to show that superconducting (SC) rubidium iron selenide Rb0.82Fe1.68Se2 exhibits antiferromagnetic (AF) spin excitations near the in-plane wave vector Q = (PI, 0) identical to that for iron arsenide superconductors. Moreover, we find that these excitations change from incommensurate to commensurate with increasing energy, and occur at the expense of spin waves associated with the coexisting sqrt(5)\timessqrt(5) block AF phase. Since angle resolved photoemission experiments reveal no evidence for hole-like Fermi surface at Gamma(0, 0), our results suggest that the Q = (PI, 0) excitations in SC Rb0.82Fe1.68Se2 come from localized moments and may have a similar origin as the hourglass-like spin excitations in copper oxide superconductors.