Role of hybridization and on-site correlations in generating plasmons in strongly correlated La2CuO4

Electronic correlation has been shown to play an important role in generating plasmons unconventionally in strongly correlated electron systems. In this work, we calculate the band structure, complex dielectric function, reflectivity, and loss function of ${\mathrm{La}}₂{\mathrm{CuO}}₄$ in its insulating and antiferromagnetic phase through first-principle calculations. We find strong evidence of unconventional plasmons that are generated by hybridizations and enhanced by on-site Coulomb correlations. Interestingly, these unconventional plasmons, predominantly located in the Cu-O planes, are driven by hybridizations between $\mathrm{La}\phantom{\rule{0.16em}{0ex}}5p$/$\mathrm{Cu}\phantom{\rule{0.16em}{0ex}}3d$ and out-of-plane ${\mathrm{O}}_{\mathrm{z}}\phantom{\rule{0.16em}{0ex}}2p$. On the other hand, in-plane oxygen ${\mathrm{O}}_{\mathrm{xy}}\phantom{\rule{0.16em}{0ex}}2p$ induces conventional plasmons. This nonuniform hybridization scheme creates an anisotropic complex dielectric function and loss function, which can be influenced by conventional plasmons, unconventional plasmons, or a mixed state between both. Our result shows that the interplay of hybridizations, particularly involving oxygen, and on-site Coulomb correlations plays an important role in determining the properties of unconventional plasmons in strongly correlated ${\mathrm{La}}₂{\mathrm{CuO}}₄$.