Another suggestion for an interband transition model was given by [Jellison 1998A]. This model is called the Tauc-Lorentz model and gives the following expression for the imaginary part of the susceptibility:
The 4 parameters of the model must be entered using wavenumber units (except for S which has the unit (1/cm)1/2) in the following dialog:
The following assignments apply:
S |
Strength (in the Jellison paper a constant A was used which is the square of S) |
ωτ |
Damping constant |
ω0 |
Resonance frequency |
ωGap |
Gap energy |
The following example shows the dielectric function obtained with this model (the parameters are those displayed in the dialog above) where a constant dielectric background of 1 has been added:
Note that the peak of the imaginary part occurs at the resonance frequency. Below the gap the imaginary part is exactly zero, i.e. there is no absorption.