In 13:20 you said its an harmonic oscillator model but eq of motion has no restoring force. I think HO model is for Lorentz model which is for dielectric material.
That is partly correct. The generalized model (Drude-Lorentz-Sommerfield model) describe an harmonic oscillator with restoring force. This is the more rigorous description of the electron gas oscillation as these electrons do experience the Coulomb attraction from the ion background. However, because the electrons are only weakly bound to the nuclei, this Coulomb attraction can be neglected and the model reduce to a simple Drude-Sommerfeld model, which indeed contains no restoring force. The Lorentz model is later introduced to account for the Interband transitions (25:25). So as you can see it does not only apply to dielectric materials. Hope this clarifies.
Great lecture professor, thanks!
In 13:20 you said its an harmonic oscillator model but eq of motion has no restoring force. I think HO model is for Lorentz model which is for dielectric material.
That is partly correct. The generalized model (Drude-Lorentz-Sommerfield model) describe an harmonic oscillator with restoring force. This is the more rigorous description of the electron gas oscillation as these electrons do experience the Coulomb attraction from the ion background. However, because the electrons are only weakly bound to the nuclei, this Coulomb attraction can be neglected and the model reduce to a simple Drude-Sommerfeld model, which indeed contains no restoring force. The Lorentz model is later introduced to account for the Interband transitions (25:25). So as you can see it does not only apply to dielectric materials.
Hope this clarifies.
Thanks! Great! :)