Eur. Phys. J. B 36, 161-167 (2003)
https://doi.org/10.1140/epjb/e2003-00330-1

Electronic state anisotropy and the Fermi surface topology of the incommensurate organic superconducting crystal (MDT-TSF)(AuI₂)

¹ Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
² National Institute for Materials Science, Tsukuba, Ibaraki 305-0003, Japan
³ Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa-shi, Chiba 277-8581, Japan
⁴ Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan

Corresponding author: ^a kawamoto@o.cc.titech.ac.jp

Received: 15 August 2003
Published online: 8 December 2003

Abstract

The Fermi surface (FS) shape of the organic superconductor (MDT-TSF)(AuI₂)_0.436 with an incommensurate anion structure (MDT-TSF: methylenedithio-tetraselenafulvalene) has been investigated by means of the optical reflectance spectra and angular-dependent magnetoresistance oscillations (AMRO). The difference of the plasma frequencies between the interstack and the intrastack directions indicates that the overall band structure has small anisotropy (). The observation of the AMRO shows the presence of a small closed orbit, which can be assigned to the overlapped area of the large FS. This demonstrates that the incommensurate anion potential is crucial to remove the degeneracy of the energy bands on the zone boundary. The magnetoresistance peak in the fields applied within the conducting layers shows an unusually large interlayer transfer integral ( meV) among organic superconductors.