Auxiliary fermion approach to the RIXS spectrum in a doped cuprate

TL;DR

This paper introduces an auxiliary fermion method to compute RIXS spectra in doped cuprates, accounting for core hole dynamics and improving experimental agreement.

Contribution

The paper presents a novel auxiliary fermion approach for RIXS calculations that incorporates core hole effects in strongly correlated systems.

Findings

Including core hole dynamics shifts RIXS peaks to higher energy transfer.

The method improves agreement between theoretical RIXS spectra and experimental data.

Application to cuprates in the pseudogap regime demonstrates the approach's effectiveness.

Abstract

We describe a method for calculating the resonant inelastic X-ray scattering (RIXS) response---including the dynamics of the transient core hole---of many-body systems with non-trivial gap structure encoded in their single particle Green's function. Our approach introduces auxiliary fermions in order to obtain a form amenable to the determinant method of Benjamin et al. [PRL 112 247002 (2014)], and is applicable to systems where interactions are most strongly felt through a renormalization of the single particle propagator. As a test case we consider the Yang Rice Zhang ansatz describing cuprate phenomena in the underdoped `pseudogap' regime, and show that including the core hole dynamics pushes the RIXS peaks towards higher energy transfer, improving agreement with experiments.