Hall effect study of field induced quantum oscillations in (TMTSF) 2PF 6 at 10.5 KBAR

Abstract

Above a temperature dependent threshold field H th, a transverse magnetic field H parallel to c ∗ axis induces giant oscillations in the Hall voltage V H of (TMTSF) 2PF 6 under an hydrostatic pressure of 10.5 Kbar.Hysteresis are observed only when the Hall voltage goes from condensed holes (V H < O) to condensed electrons (V H > O) : this is the signature of first order transitions between various SDW sub-phases, as for (TMTSF) 2C lO 4 in the relaxed state. But each SDW sub-phase is itself subdivided by a weakly first order transition driving the transverse nesting vector of the Fermi surface from an electron pocket to an hole one, as for (TMTSF) 2C lO 4 in the hyper-relaxed state. At a given H, the amplitude of V H increases and then saturates with decreasing temperature. Although this suggests a semi-metallic behaviour, the compound is never compensated dûe to the alternate condensation of electrons and holes with H. These features are compared with the Hall voltage results in (TMTSF) 2C lO 4.