Identifying and quantifying Su-Schrieffer-Heeger-like interactions with RIXS

TL;DR

This paper explores how resonant inelastic x-ray scattering (RIXS) can be used to identify and measure Su-Schrieffer-Heeger-like electron-phonon interactions in quantum materials, despite complex multi-particle excitations.

Contribution

It demonstrates how RIXS responses in a Hubbard-SSH model reveal coupled charge, magnetic, and lattice excitations, providing a method to quantify SSH-like interactions.

Findings

RIXS responses show coupled multi-particle excitations.

Lattice excitations couple to charge and magnetic sectors.

Method to identify and quantify SSH-like interactions.

Abstract

Su-Schrieffer-Heeger (SSH)-like electron-phonon (e-ph) interactions can drive the formation of light (bi)polarons and several novel states of matter. It is, therefore, prudent to develop experimental protocols for identifying such couplings in real materials and quantifying their strength. Here, we investigate how resonant inelastic x-ray scattering (RIXS) probes e-ph interactions in the one-dimensional half-filled Hubbard-SSH model with onsite phonons. Using the density matrix renormalization group method, we compute the full RIXS response and find that the lattice excitations generated during the scattering process inevitably couple to the system's charge and magnetic sectors, resulting in combined multi-particle excitations that cannot be easily disentangled from one another. While this aspect complicates the interpretation of RIXS experiments, we outline how it can be leveraged to identify and quantify SSH-like interactions in quantum materials.