At distance approximately 100nm of emitting tips (CNTs for example) a femto second electron bunch could be populated of -say- 30 electrons where inter electron distance is very low, say
Does a cold electron plasma in vacuum belong to correlated system you study ?
Yes, it is, for at low densities it can form the fermion condensation and Wigner’s crystal. This is possible due to strong correlations, see e.g. "Interplay between fermion condensation and density wave