Unconventional spin density wave in (TMTSF)2PF6 below T☆≈4 K -: art. no. 235117

The presence of subphases in the spin-density wave (SDW) phase of (TMTSF)(2)PF6 below T(star)approximate to4 K has been suggested by several experiments but the nature of the new phase is still controversial. We have investigated the temperature dependence of the angular dependence of the magnetoresistance in the SDW phase which shows different features for temperatures above and below T(star)approximate to4 K. For T>4 K the magnetoresistance can be understood in terms of the Landau quantization of the quasiparticle spectrum in a magnetic field, where the imperfect nesting plays the crucial role. We propose that below T(star)approximate to4 K the new unconventional SDW (USDW) appears modifying dramatically the quasiparticle spectrum. Unlike conventional SDW the order parameter of USDW depends on the quasiparticle momentum Delta(1)(k)proportional tocos 2bk(y). The present model describes many features of the angular dependence of magnetoresistance reasonably well. Therefore, we may conclude that the subphase in (TMTSF)(2)PF6 below T(star)approximate to4 K is described as SDW plus USDW.