Spin anisotropy of the resonance in superconducting FeSe0.5Te0.5

TL;DR

This study uses polarized-neutron scattering to analyze spin fluctuations in superconducting FeSe0.5Te0.5, revealing an anisotropic resonance peak below T_c that supports a singlet pairing state with s^{} symmetry.

Contribution

First to resolve spin fluctuation components in FeSe0.5Te0.5, demonstrating anisotropic resonance and supporting s^{} pairing symmetry in this superconductor.

Findings

Resonance at 6.5 meV develops below T_c

Resonance peak is anisotropic, with in-plane component larger

Magnetic fluctuations are isotropic away from the resonance

Abstract

We have used polarized-neutron inelastic scattering to resolve the spin fluctuations in superconducting FeSe0.5Te0.5 into components parallel and perpendicular to the layers. A spin resonance at an energy of 6.5 meV is observed to develop below T_c in both fluctuation components. The resonance peak is anisotropic, with the in-plane component slightly larger than the out-of-plane component. Away from the resonance peak the magnetic fluctuations are isotropic in the energy range studied. The results are consistent with a dominant singlet pairing state with s^{\pm} symmetry, with a possible minority component of different symmetry.