Fermi surface reconstruction in strongly correlated Fermi systems as a first-order phase transition

A quantum phase transition in strongly correlated Fermi systems beyond the topological quantum critical point has been studied using the Fermi liquid approach. The transition takes place between topologically equivalent states with three Fermi surface sheets, but one of them is characterized by a quasiparticle halo in the quasiparticle momentum distribution $n(p)$, and the other one is characterized by a hole pocket. It has been found that the transition between these states is a first-order phase transition for the interaction constant $g$ and temperature $T$. The phase diagram in the vicinity of this transition has been constructed.