Reciprocal-space structure and dispersion of the magnetic resonant mode in the superconducting phase of Rb(x)Fe(2-y)Se2 single crystals

TL;DR

This study uses inelastic neutron scattering to analyze the magnetic resonant mode in Rb0.8Fe1.6Se2, revealing its quasi-two-dimensional nature, in-plane elliptical structure, and energy-dependent dispersion, supporting an itinerant electron origin.

Contribution

It provides detailed reciprocal-space characterization of the magnetic resonance in Rb0.8Fe1.6Se2, highlighting its 2D structure and dispersion, and links it to Fermi surface nesting, which is novel for this compound.

Findings

Magnetic resonance has a quasi-2D character.

Resonance exhibits an in-plane elliptical peak structure.

Resonance position depends on energy, indicating dispersion.

Abstract

Inelastic neutron scattering is employed to study the reciprocal-space structure and dispersion of magnetic excitations in the normal and superconducting states of single-crystalline Rb0.8Fe1.6Se2. We show that the recently discovered magnetic resonant mode in this compound has a quasi-two-dimensional character, similar to overdoped iron-pnictide superconductors. Moreover, it has a rich in-plane structure that is dominated by four elliptical peaks, symmetrically surrounding the Brillouin zone corner, without sqrt(5) x sqrt(5) reconstruction. We also present evidence for the dispersion of the resonance peak, as its position in momentum space depends on energy. Comparison of our findings with the results of band structure calculations provides strong support for the itinerant origin of the observed signal. It can be traced back to the nesting of electron-like Fermi pockets in the doped metallic phase of the sample in the absence of iron-vacancy ordering.