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Magnetic Field Dependent Effective Mass in the Organic Superconductor κ-(BEDT-TTF)_{2}I_{3}

100%

Balthes E., Schweitzer D., Heinen I., Keller H., Biberacher W., Jansen A., Steep E.

Acta Physica Polonica A

1995

vol. 87

issue 4-5

767-772

κ-(BEDT-TTF)_{2}I_{3} is an electronically extreme two-dimensional organic metal with a superconducting transition at around 4 K. In magnetic fields above 12 T the effective mass, as obtained from the temperature dependence of the amplitudes of Shubnikov-de Haas oscillations, is magnetic field dependent as long as the magnetic field is arranged perpendicular to the conducting planes. In contrast to this, by turning the magnetic field by 27° or even only 9° the observed effective mass (as obtained from Shubnikov-de Haas and de Haas-van Alphen measurements) is field independent. We suppose that the occurrence of anyons at temperatures below 1 K in fields above 12 T is the reason for the observed field dependence of the effective mass.

Investigations of Fermi Surfaces and Effective Masses of the Organic Superconductors (BEDO-TTF)_{2}ReO_{4}(H_{2}O) and κ-(BEDT-TTF)_{2}I_{3} by Shubnikov-de Haas and de Haas-van Alphen Measurements

84%

Schweitzer D., Balthes E., Karlich S., Heinen I., Keller H. J., Strunz W., Biberacher W., Jansen A. G. M., Steep E.

Acta Physica Polonica A

1995

vol. 87

issue 4-5

749-759

The Fermi surfaces and effective masses of (BEDO-TTF)_{2}ReO_{4}(H_{2}0) and κ-(BEDT-TTF)_{2}I_{3} 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)_{2}ReO_{4}(H_{2}0) 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)_{2}I_{3} 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)_{2}I_{3} 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°.

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2 Acta Physica Polonica A

2 1995

2 Balthes E.

2 Biberacher W.

2 Heinen I.

2 Schweitzer D.

2 Steep E.

1 Jansen A.

1 Jansen A. G. M.

1 Karlich S.

1 Keller H.

1 Keller H. J.

1 Strunz W.

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Magnetic Field Dependent Effective Mass in the Organic Superconductor κ-(BEDT-TTF)_{2}I_{3}

Investigations of Fermi Surfaces and Effective Masses of the Organic Superconductors (BEDO-TTF)_{2}ReO_{4}(H_{2}O) and κ-(BEDT-TTF)_{2}I_{3} by Shubnikov-de Haas and de Haas-van Alphen Measurements