Plasmon excitations in layered high-Tc cuprates

ANDRÉS GRECO; YAMASE, HIROYUKI; MATÍAS BEJAS

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2016 vol. 94 p. 1 - 8

1098-0121

Motivated by the recent resonant inelastic x-ray scattering (RIXS)  experiment for the electron-doped cuprates Nd_{2−x}Ce_xCuO_4 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 featurewith 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 .