Q Dependence of Magnetic Resonance Mode on FeTe$_{0.5}$Se$_{0.5}$ Studied by Inelastic Neutron Scattering

TL;DR

This study investigates the Q-dependent magnetic resonance mode in FeTe$_{0.5}$Se$_{0.5}$ using inelastic neutron scattering, revealing non-uniform enhancement around specific wave vectors consistent with s$_{ ext{±}}$ wave pairing.

Contribution

It provides the first detailed Q-dependent analysis of magnetic resonance modes in FeTe$_{0.5}$Se$_{0.5}$, supporting the s$_{ ext{±}}$ wave pairing symmetry in this superconductor.

Findings

Magnetic resonance enhancement is limited around Q = (π, 0).

Enhancement is non-uniform across different Q vectors.

Results align with theoretical models of s$_{ ext{±}}$ wave superconductivity.

Abstract

Inelastic neutron scattering measurements have been performed on a superconducting single crystal FeTe$_{0.5}$Se$_{0.5}$ to examine the ${\bf Q}$-dependent enhancement of the dynamical structure factor, $S({\bf Q},E)$, from ${\bf Q}$ = (0, 0) to ($\pi$, $\pi$), including ($\pi$, 0) in the superconducting state. In most of iron-based superconductors, $S({\bf Q},E)$ is enhanced at ${\bf Q}$ = ($\pi$, 0), where the "magnetic resonance mode" is commonly observed in the unfolded Brillouin zone. Constant-$E$ cuts of $S({\bf Q},E)$ suggest that the enhancement is not uniform in the magnetic excitation, and limited around ${\bf Q}$ = ($\pi$, 0). This result is consistent with the theoretical simulation of the magnetic resonance mode due to the Bardeen$-$Cooper$-$Schrieffer coherence factor with the sign-reversing order parameter of s$_{\pm}$ wave.