Regime of Fermi gas or liquid?

[SadScholar]

Hi, I was wondering if anyone could clarify for me what the correct regime is for treating the electrons in a material as a Fermi gas. When is it that you must use Fermi liquid theory?

 

[vkroom]

In general Fermi liquid description is valid when

1. the interaction is short ranged.
2. the interaction energy scale is smaller than the kinetic energy of the electrons.

Although for short range interactions one can still get fermi liquids at relatively high (interaction energy) / (kinetic energy) ratio, for example in heavy fermion compunds, it is unclear to me where the limit of this ratio exactly lies.

 

[SadScholar]

Ah ok. Thanks for your help!