Abstract
Magnetotransport measurements have been made for quasi-two-dimensional η -Mo4O11 crystals in its charge-density-wave (CDW) phases along the crystallographic a*-, b-, and c-axes at low temperatures 0.3--4.2, K in magnetic fields up to 11, T. The diagonal components ρ xx (or b-axis), ρ yy (c-axis), and ρ zz (a*-axis) of the resistivity tensor are highly anisotropic (ρ xx<ρ yy<< ρ zz; ρ zz/ρ xx-- 102). Computer simulations for the magnetic field dependence of ρ xx, ρ yy, and ρ xy are made using a multicarrier model, in good agreement with the observations. From the in-plane anisotropy, we have estimated the anisotropic shape of the Fermi surfaces. These anisotropic properties are discussed by considering the characteristic crystal structure and conduction process via conducting and insulating layers along the z-axis. Furthermore, in view of the existing band model of this material and the data analyses, the observed quantum oscillations are not simply due to Shubnikov de-Haas oscillations but to some magnetic-field induced phase transition, as found for low-dimensional organic Bechgaard salts, the essence of which is the presence of hidden quasi-one-dimensional Fermi surface.
