Negative Hall plateaus and quantum Hall effect in (TMTSF)2PF6

We present our study of negative Hall plateaus associated with the magnetic-field-induced spin-density waves (FISDW). Slightly above the the pressure necessary to stabilize superconductivity, the quantum Hall effect associated with the field-induced spin density waves is interrupted by several negative Hall plateaus and an in-between phase. Quantizations of the negative Hall plateaus suggests that these states may be identified as FISDW states with negative quantum numbers. The in-between phase occurs from splitting of a phase boundary deep inside the FISDW diagram and is reminiscent of the previously suggested arborescence. [S0163-1829(99)05915-9].