Figure 2 (IMAGE) Japan Science and Technology Agency Caption Comparison of optical conductivity spectra between the charge model and the extended Hubbard model. Optical conductivity spectra for a system consisting of 14 atoms are shown. The spectrum calculated from the charge model (red slid line) quantitatively coincides with that calculated from the extended Hubbard model (black broken), while that calculated without charge fluctuation (blue solid) shifts about 2 eV (electron volt). Credit 2019 The American Physical Society Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.