Evidence for core-hole-mediated inelastic x-ray scattering from metallic Fe$_{1.087}$Te

TL;DR

This study uses high-resolution RIXS to explore electronic and lattice interactions in metallic Fe$_{1.087}$Te, revealing many-body effects and the importance of lattice contributions at high energy transfers.

Contribution

It provides the first detailed RIXS analysis of metallic Fe$_{1.087}$Te, highlighting the interplay of electron correlations and lattice effects in inelastic scattering.

Findings

Observation of many-body resonant Raman effects at low energy transfer.

Identification of exponential lineshape indicating lattice involvement at high energy transfer.

Evidence that both electronic and lattice degrees of freedom influence RIXS spectra in metals.

Abstract

We present a detailed analysis of resonant inelastic scattering (RIXS) from Fe$_{1.087}$Te with unprecedented energy resolution. In contrast to the sharp peaks typically seen in insulating systems at the transition metal $L_3$ edge, we observe spectra which show different characteristic features. For low energy transfer, we experimentally observe theoretically predicted many-body effects of resonant Raman scattering from a non-interacting gas of fermions. Furthermore, we find that limitations to this many-body electron-only theory are realized at high Raman shift, where an exponential lineshape reveals an energy scale not present in these considerations. This regime, identified as emission, requires considerations of lattice degrees of freedom to understand the lineshape. We argue that both observations are intrinsic general features of many-body physics of metals.