For MAX phase, it has the metallic nature from the analysis of DOS and band structure, and it can change from metallic to delectric material when the incident light is larger than the bulk plasma frequency of the material. Here, I have a problem: For metallic materials the static dielectric constant should go to infinity. I'm curious why that is not the case here. In addition, what's the meaning of static dielectric constant for MAX phase?
What makes you say that " the static conductivity has nothing to do with the dielectric constant", Mikhail? If we were to model the metallic state within the Drude picture, then evidently we get a diverging Re(\epsilon), don't we? (Likewise, we could say that a steady current is equivalent to a diverging polarizability in some sense.)
@Li Xiao-Hong, what is your source of information stating that the static dielectric constant is finite in the MAX phases in general? Thanks for sharing.
An ideal conductor is not just an infinite dielectric constant. It is not only infinitely large but also "infinitely" imaginary. But that does not affect bound charges. Should the field penetrate into the material it would polarize it. Free charges prevent the penetration, but virtual reaction of bound charges remains. Every possible virtual transition to upper states contributes to the dielectric constant. Of course it is masked, dwarfed by conductivity.
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