E. Balthes et al., ANOMALOUS BEHAVIOR OF MAGNETO-QUANTUM OSCILLATIONS IN THE ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)(2)I-3, Zeitschrift fur Physik. B, Condensed matter, 99(2), 1996, pp. 163-171
kappa-(BEDT-TTF)(2)I-3 is an extreme case of an electronically two-dim
ensional (2D) organic metal with a superconducting transition at aroun
d 4 K. In magnetic fields up to 27 T the field, angular and the temper
ature dependence of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (S
dH) oscillation amplitudes were investigated. From the temperature dep
endence of the oscillation amplitudes the cyclotron effective mass m
was investigated using Lifshitz-Kosevich formula (LK) and the surprisi
ng result is, that m appears to be magnetic field dependent as soon a
s the magnetic field is applied exactly perpendicular to the conductin
g planes so that the cyclotron orbit lies within those planes (i.e. Th
eta = 0 degrees), but field independent at Theta not equal 0 degrees.
It is shown that the LK formula can satisfactorily be used for the int
erpretation of all data obtained at Theta not equal 0 degrees but not
in the case where Theta = 0 degrees. An explanation of the anomalous d
ata at Theta = 0 degrees can furthermore neither be given satisfactori
ly by the descriptions of magneto-quantum oscillations in 2D electroni
c systems nor by the occurrence of magnetic interaction effects (MI).
Tentatively, the observed smaller oscillation amplitudes in kappa-(BED
T-TTF)(2)I-3 at Theta = 0 degrees above 12 T and below 1 K compared to
the standard LK theory will be discussed in terms of a loss in the nu
mber of fermions by the occurrence of quasiparticles with fractional s
tatistics.