Optical response and band structure of LiCoO2 including electron-hole interaction effects

The optical response functions and band structures of LiCoO2 are studied at different levels of approximation, from density functional theory (DFT) in the generalized gradient approximation (GGA) to quasiparticle selfconsistent QSGW (with G for Green's function and W for screened Coulomb interaction) without and with ladder diagrams (QSGW) and the Bethe Salpeter Equation (BSE) approach. The QSGW method is found to strongly overestimate the band gap and electron-hole or excitonic effects are found to be important. They lower the quasiparticle gap by only about 11% but the lowest energy peaks in absorption are found to be excitonic in nature. The contributions from different band to band transitions and the relation of excitons to band-to-band transitions are analyzed. The excitons are found to be strongly localized. A comparison to experimental data is presented.

Automated summary

The optical response functions and band structures of LiCoO2 were studied using various levels of approximation, from DFT in GGA to QSGW with and without ladder diagrams as well as the BSE approach. The QSGW method overestimated the band gap, with electron-hole or excitonic effects influencing the quasiparticle gap and absorption peaks. The excitons were found to be strongly localized and comparisons to experimental data were made.