DENSITY WAVE FORMATION IN LOW-DIMENSIONAL ELECTRON-SYSTEMS UNDER AN INCOMMENSURATE POTENTIAL

The charge or spin density wave (DW) formation in one-dimensional (1D) electron systems under an external incommensurate potential is shown to be characterized by infinitely many order parameters (MOP) and infi nitely many mean-field solutions with almost degenerate energies. We i nvestigate various properties of such a DW state, including the band s tructure and the relative magnitude of the OP's as functions of the st rength and period of the external potential. The complexity of the con figuration space of the mean-field solutions is described by ultrametr icity. The observed field-induced SDW transition of 2D systems such as (TMTSF)2X is discussed where the magnetic field plays a role of the i ncommensurate potential in this context.