Dual structure in the charge excitation spectrum of electron-doped cuprates

TL;DR

This paper investigates the charge excitation spectrum in electron-doped cuprates using a layered t-J model with Coulomb interactions, revealing a dual structure of low- and high-energy charge fluctuations influenced by interlayer coupling.

Contribution

It introduces a detailed analysis of the dual charge excitation spectrum in electron-doped cuprates, emphasizing the role of interlayer coupling often overlooked in previous models.

Findings

Low-energy charge excitations are bond-charge fluctuations driven by exchange interactions.

High-energy charge excitations are plasmon modes above the particle-hole continuum.

Interlayer coupling significantly affects high-energy charge excitations.

Abstract

Motivated by the recent resonant x-ray scattering (RXS) and resonant inelastic x-ray scattering (RIXS) experiments in electron-doped cuprates, we study the charge excitation spectrum in a layered t-J model with the long-range Coulomb interaction. We show that the spectrum is not dominated by a specific type of charge excitations, but by different kinds of charge fluctuations, and is characterized by a dual structure in the energy space. Low-energy charge excitations correspond to various types of bond-charge fluctuations driven by the exchange term (J-term) whereas high-energy charge excitations are due to usual on-site charge fluctuations and correspond to plasmon excitations above the particle-hole continuum. The interlayer coupling, which is frequently neglected in many theoretical studies, is particularly important to the high-energy charge excitations.