Reentrant Phase Diagram of Two-Dimensional Electron Gas

We study the phase diagram of an electron on a square lattice in a transverse magnetic field. Using a renormalization scheme, we show that the inequality of the two next-nearest neighbor couplings destroys the fat critical regime above the bicritical line and replaces it with another reentrant extended phase. Furthermore, the universal strange attractor describing self-similar fluctuations of the localized phase is replaced by a new fixed point. The reentrant extended phase and the new fixed point of the localized phase belong to the universality class of an anisotropic triangular lattice.