E. Balthes et al., MAGNETIC-FIELD DEPENDENT EFFECTIVE-MASS IN THE ORGANIC SUPERCONDUCTORKAPPA-(BEDT-TTF)(2)I-3, Acta Physica Polonica. A, 87(4-5), 1995, pp. 767-772
kappa-(BEDT-TTF)(2)I-3 is an electronically extreme two-dimensional or
ganic metal with a superconducting transition at around 4 K. In magnet
ic fields above 12 T the effective mass, as obtained from the temperat
ure dependence of the amplitudes of Shubnikov-de Haas oscillations, is
magnetic field dependent as long as the magnetic field is arranged pe
rpendicular to the conducting planes. In contrast to this, by turning
the magnetic field by 27 degrees or even only 9 degrees the observed e
ffective mass (as obtained from Shubnikov-de Haas and de Haas-van Alph
en 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.