Close inspection of plasmon excitations in cuprate superconductors

Abstract

Recently resonant inelastic x-ray scattering experiments reported fine details of the charge excitations around the in-plane momentum q∥=(0,0) for various doping rates in electron-doped cuprates La2−xCexCuO4. We find that those new experimental data are well captured by acousticlike plasmon excitations in a microscopic study of the layered t−J model with the long-range Coulomb interaction. The acousticlike plasmon is not a usual plasmon typical to the two-dimensional system, but has a small gap proportional to the interlayer hopping tz.