Optical Absorption in La2−xSrxCuO4 Epitaxial Thin Films

Abstract

An experimental study on optical absorption is described for La2− x Sr x Cu4 (x = 0 ~ 0.36) c-axis oriented epitaxial films. In addition to the fundamental absorption corresponding to the energy gap of 2 eV, an anomalous absorption band is seen in the optical transmission spectra. This absorption, the intensity of which increases with Sr doping, implies Sr doping induces electronic states within the gap of La2CuO4. With further Sr doping, the density of states forms a band about 1 eV wide and centered at about 0.5 eV above the top of the original valence band. This emerging density of states within the gap is totally at variance with the conventional rigid band model, and seems to be inherent to the high T c superconductors.KeywordsFermi LevelOptical AbsorptionDoping LevelElectron Energy Loss SpectroscopyEpitaxial FilmThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.