Metal–spin-density-wave transition in a quasi-one-dimensional conductor: Pressure and magnetic field effects

This paper provides a mean-field description of the spin-density-wave (SDW) state of a quasi-one-dimensional (quasi-1D) conductor with an open Fermi surface, as well as of its behavior in low magnetic field. The variation of simple quantities with the degree of nesting is worked out: These quantities are the specific-heat jump at the metal-SDW transition and its variation in a magnetic field, and the increase of the transition temperature with the field. A quadratic behavior $T_c$(H) reproduces the experimental situation in the Bechgaard salt (TMTSF${)}_2$ ${\mathrm{PF}}_6$ (TMTSF being tetramethyltetraselenafulvalene) in which other experiments performed at different pressures should provide a test for such a mean-field low-coupling description.