Tight-binding calculation of the optical conductivity in NaxCoO2

Optical conductivity in NaxCoO2 is calculated with tight binding approximation. The calculated gross features agree with the experimental findings. Interband transitions between nearly degenerate t2g bands bring about absorption in the mid-infrared and near infrared regions. Structures observed at higher energies are also quite well reproduced with the present calculation. Possible effects of electron correlation are also briefly discussed.