Charge ordering due to topological reconstruction of the Fermi surface

Numerous experiments in recent years indicate presence of charge ordering such as charge density wave (CDW) in layered 2D materials among which we single out HiTC cuprates in pseudogap regime and intercalated graphite. External magnetic field leads to the stabilization of long-ranged CDW. We show that topological reconstruction of the Fermi surface (FS), appearing as a consequence of spontaneously created CDW of such wave vector to bring closed electron pockets to touching, lowers the total energy of electron condensate. Opening the gap Δ at the touching points transforms the chain of closed electron pockets into a continuous open FS. Such CDW appears as rather peculiar quantum phase transition, with nonstandard dependence of condensate energy on Δ for coupling constant of responsible interaction exceeding the critical value [PRB 97 235439]. It appears in the regime opposite to the standard CDW mechanism related to the FS nesting. Introducing external magnetic field, and taking into account magnetic breakdown, even more strengthens the spontaneous FS reconstruction because open FS does not undergo the energy-increasing Landau quantization [PRB 100 115108]. Reconstruction in two directions changes sign of the Hall constant.