Investigations of Fermi Surfaces and Effective Masses of the Organic Superconductors (BEDO-TTF)2ReO4(H2O) and κ-(BEDT-TTF)2I3 by Shubnikov-de Haas and de Haas-van Alphen Measurements |
| D. Schweitzer, E. Balthes, S. Karlich 3. Physik. Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany I. Heinen, H.J. Keller, W. Strunz Anorg.-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany W. Biberacher Walther Meissner Institut, Walther-Meissner-Str. 8, 85748 Garching, Germany A.G.M. Jansen and E. Steep High Magnetic Field Laboratory, MPI für Festkörperforschung, 38042 Grenoble Cedex 9, France |
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| The Fermi surfaces and effective masses of (BEDO-TTF)2ReO4(H20) and κ-(BEDT-TTF)2I3 were investigated by Shubnikov–de Haas (SdH) and de Haas–van Alphen (dHvA) measurements in magnetic fields up to 27 T in the temperature range from 0.5 K to 4.2 K. Two small closed pockets (0.7% and 1.5% of the first Brillouin zone) are observed in (BEDO-TTF)2ReO4(H20) corresponding very well with two cross-sectional areas of the Fermi surfaces obtained for a hole and an electron pocket from tight binding calculations. In contrast, in κ-(BEDT-TTF)2I3 two relatively large closed sections (13% and 85% of the first Brillouin zone) of the Fermi surfaces are observed, again confirming the tight binding calculations. For κ-(BEDT-TTF)2I3 in magnetic fields above 12 T the effective mass for the larger orbit, as obtained from the temperature dependence of the SdH-oscillation amplitudes, is magnetic field dependent as long as the field is arranged perpendicular to the conducting planes (Θ = 0°). In contrast, from dHvA measurements - which were performed by turning the magnetic field by 27° with respect to the SdH experiments - the observed effective mass is field independent. We suppose that the occurrence of anyons at temperatures below 1 K and in fields above 12 T might be the reason for the observed field dependence of the effective mass in the SdH investigations under the special angle 0°. |
| DOI: 10.12693/APhysPolA.87.749 PACS numbers: 74.70.Kn, 71.25.Hc, 71.25.Jd |