Coupling of spin and orbital excitations in the iron-based superconductor FeSe(0.5)Te(0.5)

TL;DR

This study combines neutron scattering and photoemission data to explore the coupling of spin and orbital excitations in FeSe(0.5)Te(0.5), revealing complex magnetic behavior potentially linked to superconductivity.

Contribution

It introduces a model emphasizing the coupling of spin and orbital correlations to explain magnetic dispersion in FeSe(0.5)Te(0.5), challenging existing spin-wave and nesting theories.

Findings

Magnetic excitations disperse only transversely to the wave vector

Fermi surface consists of four incommensurate pockets

Spin resonance occurs at an incommensurate wave vector

Abstract

We present a combined analysis of neutron scattering and photoemission measurements on superconducting FeSe(0.5)Te(0.5). The low-energy magnetic excitations disperse only in the direction transverse to the characteristic wave vector (1/2,0,0), whereas the electronic Fermi surface near (1/2,0,0) appears to consist of four incommensurate pockets. While the spin resonance occurs at an incommensurate wave vector compatible with nesting, neither spin-wave nor Fermi-surface-nesting models can describe the magnetic dispersion. We propose that a coupling of spin and orbital correlations is key to explaining this behavior. If correct, it follows that these nematic fluctuations are involved in the resonance and could be relevant to the pairing mechanism.