Anomalous damping effects of magneto-quantum oscillations in the extremely 2D electronic system κ-(BEDT-TTF)2I3

The electronic system of the organic superconductor kappa-(BEDT-TTF)(2)I-3 (BEDT-TTF = bis(ethylenedithiolo) tetrathiafulvalene) is identified as extremely two-dimensional (2D). The topology of the Fermi surface (FS) was investigated by means of Shubnikov-de Haas (SdH) as well as de Haas-van Alphen (dHvA) experiments focusing on the verification of the 2D character of the system. This two-dimensionality specially takes effect as soon as the magnetic field is oriented exactly perpendicular to the conducting planes (i.e. Theta=0 degrees). Under such conditions strong anomalous damping effects in the field and temperature dependence of quantum oscillation amplitudes are observed. These anomalous damping effects are discussed in terms of the occurrence of quasi-particle excitations with fractional statistics (QPFS) which may only occur in extremely 2D systems at high magnetic fields and low temperatures (i.e., only when (h) over bar omega(c) much greater than k(B)T). Taking up these requirements, the aim of this work is to quanti fy the extreme two-dimensionality of the electronic system of kappa-(BEDT-TTF)(2)I-3 and to show that the observed damping effects in fact are determined by the ratio (h) over bar omega(c)/k(B)T. These facts may support the interpretation of the observed damping effects of quantum oscillation amplitudes at high magnetic fields, low temperatures and Theta=0 degrees as generated by the possible occurrence of such QPFS. (C) 1998 Elsevier Science S.A. All rights reserved.