Soft striped magnetic fluctuations competing with superconductivity in Fe_{1+x}Te

TL;DR

This study uses neutron spectroscopy to explore magnetic fluctuations in Fe_{1+x}Te, revealing incommensurate stripe-like excitations that compete with superconductivity and challenge simple spin state models.

Contribution

It provides new insights into the magnetic excitation spectrum and orbital state complexities in Fe_{1+x}Te, highlighting the competition between magnetic order and superconductivity.

Findings

Incommensurate stripe-like excitations soften with more interstitial iron.

Energy crossover defines an hour-glass dispersion pattern.

Integrated intensity suggests Fe^{2+} is in a superposition of orbital states.

Abstract

Neutron spectroscopy is used to investigate the magnetic fluctuations in Fe_{1+x}Te - a parent compound of chalcogenide superconductors. Incommensurate "stripe-like" excitations soften with increased interstitial iron concentration. The energy crossover from incommensurate to stripy fluctuations defines an apparent hour-glass dispersion. Application of sum rules of neutron scattering find that the integrated intensity is inconsistent with an S=1 Fe^{2+} ground state and significantly less than S=2 predicted from weak crystal field arguments pointing towards the Fe^{2+} being in a superposition of orbital states. The results suggest that a highly anisotropic order competes with superconductivity in chalcogenide systems.