Plasmon excitations in layered high-Tc cuprates

MATÍAS BEJAS; YAMASE, HIROYUKI; ANDRÉS GRECO

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Sociaty

Lugar: New York; Año: 2016 vol. 94 p. 75139 - 75145

0163-1829

Motivated by the recent resonant inelastic x-ray scattering (RIXS) experiment for the electron-doped cuprates Nd2−xCexCuO4 with x≈0.15, we compute the density-density correlation function in the t−J model on a square lattice by including interlayer hopping and the long-range Coulomb interaction. We find that collective charge excitations are realized not inside the particle-hole continuum, but above the continuum as plasmons. The plasmon mode has a rather flat dispersion near the in-plane momentum q∥=(0,0) with a typical excitation energy of the order of the intralayer hopping t when the out-of-plane momentum qz is zero. However, when qz becomes finite, the plasmon dispersion changes drastically near q∥=(0,0), leading to a strong dispersive feature with an excitation gap scaled by the interlayer hopping tz. We discuss the mode recently observed by RIXS near q∥=(0,0) in terms of the plasmon mode with a finite qz.