de Haas-van Alphen studies and Fermi surface properties of organic superconductors (ET)(sub 2)X.

摘要

De Haas-van Alphen (dHvA) measurements of organic superconductors (ET)(sub 2)X, where ET stands for bis(ethylene)dithiotetrathiafulvalene (or BEDT-TTF) and X = IBr(sub 2), (NH(sub 4))Hg(SCN)(sub 4) and Cu(NCS)(sub 2) are reported. The strong two-dimensionality of the Fermi surface (FS) is clearly seen by the perfect 1/cos((Theta))-behavior of the dHvA frequency. The distinctive kind of beating and the angular dependence of the dHvA signal in (beta)-(ET)(sub 2)IBr(sub 2) gives clear evidence for a lightly corrugated structure of the FS. Due to the nearly cylinder-shape of the FS the bare band structure effective mass, m(sub b), also shows a 1/cos((Theta))-dependence which is responsible for spin splitting zeros at certain angles. At these points, where the fundamental amplitude of the dHvA signal is vanishing, m(sub b) could exactly be determined and by comparison with the independently measured cyclotron effective mass the electron-phonon coupling constant could be estimated. 17 refs, 5 figs.