Electronic Properties of Quasi-Two-Dimensional Organic Metals

Abstract

Shubnikov-de Haas and de Haas-van Alphen quantum oscillation (QO) experiments on the organic metals (BEDT-TTF)4[Ni(dto)2] and κ-(BEDT-TTF)2I3 are reported. The results show that for the first material a slightly warped Fermi surface (FS) exists, which causes that in the entire field, temperature and angular range covered by the experiments the standard Lifshitz-Kosevich (LK) theory, which describes QOs in three-dimensional electronic systems, applies very well. In κ-(BEDT-TTF)2I3, however, the FS is only negligibly warped, so that the electronic system is highly two-dimensional (2D). Nevertheless, as long as the magnetic field is declined from the special orientation exactly perpendicular to the conducting BEDT-TTF layers, the LK theory is still very well applicable. In contrast, as soon as the magnetic field is arranged exactly perpendicular to the conducting planes and exceeds 12T, strong anomalous damping effects in the SdH amplitudes occur at temperatures below IK. This behaviour cannot be explained by the LK theory, even considering corrections, e.g., for 2D systems. It is shown that electron localizations might explain the observed strong anomalous damping effects.