Superconducting properties and Fermi-surface topology of the quasi-two-dimensional organic superconductor λ-(BETS)₂GaCl₄(BETS≡bis(ethylene-dithio)tetraselenafulvalene)

Abstract

The Fermi surface topology of the organic superconductor \\lbets has been\ndetermined using the Shubnikov-de Haas and magnetic breakdown effects and\nangle-dependent magnetoresistance oscillations. The former experiments were\ncarried out in pulsed fields of up to 60 T, whereas the latter employed\nquasistatic fields of up to 30 T. All of these data show that the Fermi-surface\ntopology of \\lbets is very similar to that of the most heavily-studied organic\nsuperconductor, \\cuscn, except in one important respect; the interplane\ntransfer integral in \\lbets is a factor $\\sim 10$ larger than that in \\cuscn .\nThe increased three-dimensionality of \\lbets is manifested in radiofrequency\npenetration-depth measurements, which show a clear dimensional crossover in the\nbehaviour of $H_{c2}(T)$. The radiofrequency measurements have also been used\nto extract the Labusch parameter determining the fluxoid interactions as a\nfunction of temperature, and to map the flux-lattice melting curve.\n