Unconventional spin density wave in Bechgaard salt

¹ The Abdus Salam ICTP - Strada Costiera 11, Trieste, I-34014, Italy
² Department of Physics and Astronomy, University of Southern California Los Angeles CA 90089-0484, USA
³ Department of Physics, Budapest University of Technology and Economics H-1521 Budapest, Hungary
⁴ Research Institute for Solid State Physics and Optics P.O. Box 49, H-1525 Budapest, Hungary

Received: 27 May 2004
Accepted: 19 July 2004

Abstract

The quasi–one-dimensional organic conductor Bechgaard salts X with , , , etc. are well known for the variety of their ground states: spin density wave (SDW), field-induced spin density wave (FISDW) and triplet superconductivity. We propose here that the unconventional spin density wave (USDW) occupies a large area of the P-B phase diagram, where SDW is suppressed by pressure (P) and superconductivity by magnetic field (B) and FISDW is still absent. USDW describes the striking angular dependent magnetoresistance (ADMR) seen in this area of the phase diagram, when the magnetic field is rotated in the c^*- plane. Also the Lebed resonances are naturally interpreted in terms of the imperfect nesting term.