INFINITE CASCADES OF FIELD-INDUCED SPIN-DENSITY WAVE STATES IN ANISOTROPIC 2-DIMENSIONAL CONDUCTORS

To explain recursive cascades of the field-induced spin density wave phase in organic conductors discovered recently, a standard model or two-dimensional anisotropic Hubbard model under a perpendicular field is investigateed: the SDW ground state is found to be characterized by a set of countable many-order parameters (OP) of the Fourier components of the SDW modulation or by a distribution of these OP's. Due to interference between the lattice commensurability and magnetic length, the OP distribution differs for every rational field, resulting in a phase diagram with devil's staircase like infinite cascades.