Fermi-surface instabilities in the organic conductor (Tmtsf)₂no₃: High-pressure studies.

The study of the magnetoresistance in the organic quasi-one-dimensional conductor (TMTSF)₂NO₃ at a pressure (8 kbar) exceeding the critical pressure required for the stabilization of a conducting state at low temperature has revealed the existence of quantum oscillations with a frequency of 190 T in good agreement with an extended Hiickel-type calculation of the band structure. Unlike other members of the (TMTSF)2X series the ambient pressure SDW ground state in (TMTSF)₂NO₃ can be understood in terms of an instability involving the nesting of 2D semi-metallic Fermi surfaces.