Quantum Hall effect and anomalous transport in (TMTSF)₂PF₆

Abstract
Under low temperatures and high magnetic fields, quasi-one dimensional organic conductor (TMTSF)₂PF₆ exhibits a series of transitions to field-induced spin density wave (FISDW). Slightly above the onset of superconductivity in (TMTSF)₂PF₆, we observe a series of intervening phases that interrupt the sequence of FISDW that gives rise to the quantum Hall effect. These phases can be identified either as negative quantum numbered FISDW states or a puzzling arboresecent phase. Detailed study of the QHE in (TMTSF)₂PF₆ reveals that the transport in the FISDW phases is dominated by anomalous longitudinal resistivities ρ_xx and ρ_yy that remain finite at low temperatures. While the quantization of σ_xy is not adversely affected at high magnetic fields, the transport in the intermediate magnetic field remains complicated. In addition, the conductivity along applied magnetic field, σ_zz, cannot be easily understood in terms of three-dimensional QHE and is suggestive of the importance of inter-layer coupling.