Polarization-dependent resonant inelastic X-ray scattering study at the Cu L and O K-edge of YBa$_2$Cu$_3$O$_{7-x}$

TL;DR

This study uses polarization-dependent resonant inelastic X-ray scattering to investigate low-energy excitations in YBa2Cu3O7-x, revealing a doping-dependent multi-magnon excitation distinct from bi-magnons.

Contribution

It combines high-resolution RIXS measurements with multiplet calculations to identify and characterize multi-magnon excitations in a high-Tc superconductor.

Findings

Identified a 0.5 eV peak in O K RIXS linked to multi-magnon excitations.

Demonstrated doping, energy, and momentum dependence of the peak.

Provided a new interpretation of low-energy excitations in YBCO.

Abstract

We present a study on the high-Tc superconductor (HTSC) YBa2Cu3O7-x (YBCO) using polarization-dependent X-ray absorption and resonant inelastic X-ray scattering. High-resolution measurements using synchrotron-radiation are compared with calculations using a quasi-atomic multiplet approach performed at the Cu 2p3/2-edge of YBCO. We use a multiplet approach within the single impurity Anderson model to reproduce and understand the character of the localized low-energy excitations in YBCO. We observe a distinct peak at about 0.5 eV in O K RIXS. This peak shows dependence on doping, incident energy, and momentum transfer that suggests that it has a different origin than the previously discussed cuprate bi-magnons. Therefore, we assign it to multi-magnon excitations between the Zhang Rice bands and/or the Upper Hubbard bands, respectively.