Resonant Inelastic X-Ray Scattering Spectra of Cuprate Superconductors Predicted by Model of Fractionalized Fermions

TL;DR

This paper predicts RIXS spectra of cuprate superconductors using a fractionalized electron model, showing intensity enhancement in the superconducting phase, and suggests this as a test for unconventional electron fractionalization.

Contribution

It introduces a combined theoretical and machine learning approach to predict RIXS spectra based on electron fractionalization in cuprates, providing a new method to study strongly correlated systems.

Findings

RIXS intensity is enhanced in the superconducting phase

The fractionalized fermion model fits ARPES data well

Proposes RIXS intensity enhancement as a test for electron fractionalization

Abstract

We theoretically analyze the intensity of the resonant inelastic X-ray scattering (RIXS) based on Ansatz that the electron is fractionalized into two components. By fitting the angle resolved photoemission spectroscopy (ARPES) data of a cuprate high-$T_{\rm c}$ superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and the accompanied machine learning results obtained before by Yamaji {\it et al.} (arXiv:1903.08060), we determine the paprameters of the two-component fermion model which describes the electron fractionalization. The RIXS spectra are predicted by using this description. We find that the intensity is enhanced in the superconducting phase relative to the normal or pseudogap phase. Since the enhancement is unusual, we propose this can be used as a critical test whether the unconventional electron fractionalization captures the essence of the cuprate superconductivity. This type of combined analyses using multiple independent spectroscopy data, with the help of theoretical and machine learning insights, regarded as {\it integrated spectroscopy} opens a new route to study difficult open issues in strongly correlated electron systems.