Charge-Density-Excitation Spectrum in the t-t'-J-V Model

TL;DR

This study investigates the charge-density excitation spectrum in the t-t'-J-V model, revealing how Coulomb interactions influence phase separation and low-energy excitations, with implications for interpreting x-ray scattering experiments.

Contribution

It demonstrates the impact of finite Coulomb interaction V on charge excitations and phase separation in the t-t'-J model, highlighting the importance of V in understanding low-energy charge dynamics.

Findings

Phase separation causes strong spectral weight near q=(0,0) at low energy.

Finite V suppresses phase separation and low-energy spectral weight.

A sharp zero-sound mode emerges above the particle-hole continuum.

Abstract

We study the density-density correlation function in a large-N scheme of the t-t'-J-V model. When the nearest-neighbor Coulomb interaction V is zero, our model exhibits phase separation in a wide doping region and we obtain large spectral weight near momentum q=(0,0) at low energy, which originates from the proximity to phase separation. These features are much stronger for electron doping than for hole doping. However, once phase separation is suppressed by including a finite V, the low-energy spectral weight around q=(0,0) is substantially suppressed. Instead a sharp zero-sound mode is stabilized above the particle-hole continuum. We discuss that the presence of a moderate value of V, which is frequently neglected in the t-J model, is important to understand low-energy charge excitations especially close to q=(0,0) for electron doping. This insight should be taken into account in a future study of x-ray scattering measurements.