Regular atomic matter almost always experiences liquid-gas transition at some temperature (at sufficiently low pressure). Does anyone know if electrons in metals/semiconductors experience a similar transition sometimes?
I don't see anyone mentioning liquid-gas first order transition for electronic matter. Is there a reason why such transition cannot exist?
Liquid and gas are both disordered systems differing only for their densities. In order to have a first-order phase transition, with a liquid-gas coexistence, the pressure as a function of density must be non-strictly-monotonic because we need to have coexistence of states of different densities but at the same pressure. While such non-strictly-monotonic behavior can be found in the presence of interactions made by a long-range attractive and a short-range repulsive part, it is not possible in the case of a purely repulsive interaction like the pure Coulomb interaction between electrons.
The only possibility of introducing an attractive interaction is through the presence of additional degrees of freedom. This is the case of the phonon-mediated attraction between electrons at the basis of the Cooper pairs formation and the normal-superconductor transition.
