Figure 3 (IMAGE) Japan Science and Technology Agency Caption Optical conductivity spectra calculated by using many-body Wannier functions. <BR>(a) Comparison of the charge model and the method of the many-body Wannier functions. The method of the many-body Wannier functions well reproduces the optical conductivity spectrum calculated from the charge model for a system consisting of 40 atoms. <BR>(b) System size dependence of the spectra calculated by using the many-body Wannier functions. The spectral distribution becomes broad as the system size increases until the size reaches about 200. 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.