Theoretical study of charge excitations in high-Tc cuprate super- conductors

YAMASE, HIROYUKI; A. GRECO; M. BEJAS

Krakow

Workshop; Exotic Interactions in Quantum Correlated Materials; 2018

Narodowe Centrum Nauki (NCN, National Science Centre) and the Jagiellonian University

Motivated by recent resonant inelastic x-ray scattering (RIXS) measurements for cuprate superconductors [1,2], we study the charge excitation spectrum in the layered t-J model with the long-range Coulomb interaction. We find that the spectrum is characterized by a dual structure in the energy space [3]. A low-energy region typically less than J is occupied by various types of bond-charge fluctuations. In particular, the spectrum associated with d-wave bond-charge fluctuations exhibits a softening around the in-plane momentum q∥ = (0.5π, 0). This may explain the short-range charge order observed in electron-doped cuprates [4,5]. On the other hand, usual on-site charge excitations occur in a high-energy region and yield plasmon excitations above the particle-hole continuum. The plasmon dispersion is nearly linear in momentum around q∥ = (0, 0) with an energy gap scaled by the interlayer hopping tz for a finte qz [6]. We argue that this plasmon mode is detected in recent RIXS measurements not only in electron-doped cuprates [1,2] but also in hole-doped cuprates [1].[1] K. Ishii et al., Phys. Rev. B 96, 115148 (2017).[2] G. Dellea et al., Phys. Rev. B 96, 115117 (2017).[3] M. Bejas, H. Yamase, and A. Greco, Phys. Rev. B 96, 214513 (2017).[4] E. H. da Silva Neto et al., Science 347, 282 (2015).[5] H. Yamase, M. Bejas, and A. Greco, Europhys. Lett. 111, 57005 (2015).[6] A. Greco, H. Yamase, and M. Bejas, Phys. Rev. B 94, 075139 (2016).