Strongly correlated model of acousticlike plasmons persisting across the phase diagram of cuprate superconductors

TL;DR

This study demonstrates that a single strongly correlated layered $t$-$J$-$V$ model can consistently describe acousticlike plasmons across the entire phase diagram of cuprate superconductors, indicating persistent strong correlations.

Contribution

The paper introduces a unified $t$-$J$-$V$ model that captures plasmon behavior across doping levels, surpassing previous models in transferability and suggesting enduring strong correlations.

Findings

A single parameter set describes plasmon dispersion from underdoped to overdoped cuprates.

The plasmon mode shows limited sensitivity to phase-specific electronic phenomena.

Strong correlations persist into the heavily overdoped regime.

Abstract

Layered two-dimensional electron systems exhibit both optical and acousticlike plasmons around the Brillouin-zone center. In the layered cuprate La$_{2-x}$Sr$_x$CuO$_4$, resonant inelastic x-ray scattering (RIXS) has detected corresponding acousticlike plasmons in a low-energy regime comparable to that of other collective excitations associated with distinct regions of the cuprate phase diagram. This overlap in energy scale raises the question of whether the acousticlike plasmons are significantly influenced by phase-specific electronic phenomena, including the pseudogap, charge and spin order, superconductivity, and strange-metal behavior. Here we show that a single parameter set of the layered $t$-$J$-$V$ model, which incorporates strong correlations and the long-range Coulomb interaction $V$, consistently describes the acousticlike plasmon dispersion across all currently available RIXS data from the underdoped to the heavily overdoped regime. This transferability of a single parameter set exceeds that of earlier theoretical descriptions and supports a picture in which strong correlations persist into the heavily overdoped regime, while the collective plasmon mode exhibits only limited sensitivity to the phase-specific electronic phenomena that distinguish different regions of the phase diagram.