Hydrostatic pressure dependence of the optical absorption edge in Bi12SiO20

The optical absorption coefficients in Bi12SiO20 have been measured precisely at various hydrostatic pressures up to 40 kbar at room temperature. The interband gap for the indirect allowed transition was found to have a pressure coefficient (∂Eg/∂P)T of −1.20×10−6 eV/bar. Using the result of the pressure coefficient, it was indicated that the electron‐phonon interaction was dominant in the temperature dependence of the indirect energy gap in Bi12SiO20.