THEORETICAL STUDY OF UNCONVENTIONALLY CORRELATED PLASMON IN CUPRATES

Abstract

Recently, unconventional plasmons have been shown to exist in SrNbO3.x [1]. In this work, we calculate the band structure, complex dielectric func- tion, and loss function of La2CuO4 in its insulating and antiferromagnetic phase through first principle calculation. We have found strong evidence of unconventional plasmons that are highly dependent on U in DFT+U. Interestingly, the unconventional plasmons are present even in calculations involving exchange-correlation only interactions (bare-DFT). We find that increasing U value dramatically changes the spectra, shifts the plasmonic excitations, and even annihilates the unconventional plasmons. There is trade-off between achieving correct optical properties and correct band gap. We suspect that this is due to the simplicity of the Hubbard model, which severely affects the optical spectra. Our calculation thus have highlighted the behavior unconventional plasmons under the increased correlation ef- fects through Hubbard U in DFT+U calculations.