The Phase Diagram and the Structure of the Charge-Density-Wave State in High Magnetic Field

The properties of a charge-density wave (CDW) state in quasi-one-dimensional metals in magnetic field below the transition temperature are studied using the mean-field theory. We calculate the phase diagram and show that the CDW state with shifted wave vector in high magnetic field (CDW_x phase) has at least double-cosine modulation on the most part of the phase diagram. The transition from CDW₀ to CDW_x state below the critical temperature is accompanied by a jump of the CDW order parameter and of the wave vector rather than by their continuous increase. This implies a first order transition between these CDW states and explains the strong hysteresis accompanying this transition in many experiments. We examine how the phase diagram changes in the case of imperfect nesting. The results are applicable to different families of organic metals.