Spontaneous breaking of fourfold rotational symmetry in two-dimensional electron systems as a topological phase transition

Motivated by recent observations of C₄ symmetry breaking in strongly correlated two-dimensional electron systems on a square lattice, we analyze this phenomenon within an extended Fermi-liquid approach. It is found that the symmetry violation is triggered by a continuous topological phase transition associated with exchange of antiferromagnetic fluctuations. In contrast to predictions of mean-field theory, the structure of a part of the single-particle spectrum violating C₄ symmetry is found to be highly anisotropic, with a peak located in the vicinity of saddle points.