Splitting of resonance excitations in nearly optimally doped Ba(Fe0.94Co0.06)2As2: an inelastic neutron scattering study with polarization analysis

TL;DR

This study uses polarized inelastic neutron scattering to reveal two distinct resonance excitations in the superconducting state of Ba(Fe0.94Co0.06)2As2, showing different polarization and dispersion characteristics.

Contribution

It provides the first detailed polarization analysis of resonance excitations in this compound, identifying a split into two modes with different energies and polarization dependencies.

Findings

Discovery of two resonance modes at 4 meV and 8 meV.

The 4 meV mode is c-polarized and L-dependent.

The 8 meV mode is isotropic with weak c-axis dispersion.

Abstract

Magnetic excitations in Ba(Fe0.94Co0.06)2As2 are studied by polarized inelastic neutron scattering (INS) above and below the superconducting transition. In the superconducting state we find clear evidence for two resonance-like excitations. At a higher energy of about 8 meV there is an isotropic resonance mode with weak dispersion along the c-direction. In addition we find a lower excitation at 4 meV that appears only in the c-polarized channel and whose intensity strongly varies with the L-component of the scattering vector. These resonance excitations behave remarkably similar to the gap modes in the antiferromagnetic phase of the parent compound BaFe2As2.