de Haas–van Alphen studies of the organic superconductors α-(ET)2(NH4)Hg(SCN)4 and κ-(ET)2Cu(NCS)2 [with ET = bis(ethelenedithio)-tetrathiafulvalene]
J. Wosnitza, G. W. Crabtree, H. H. Wang, U. Geiser, J. M. Williams, K. D. Carlson
DOI 10.1103/PhysRevB.45.3018 · Physical Review B
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Abstract
We report measurements of the de Haas–van Alphen (dHvA) effect in the organic superconductors α-(ET)2(NH4)Hg(SCN)4 and κ-(ET)2Cu(NCS)2 in fields up to 15 T and temperatures down to 0.45 K. In both compounds, the perfect 1/cosθ behavior of the dHvA frequency for angles θ of the applied field up to 70° from the normal to the conducting planes shows the strong two-dimensionality of the Fermi surface (FS). The angle-dependent magnetic-breakdown orbit found in κ-(ET)2Cu(NCS)2 hints at a small warping of the FS. The unusual angular dependence of the dHvA amplitude with up to 4 spin splitting zeros is quantitatively explainable by a 1/cosθ dependence of the bare band cyclotron-resonance effective mass. This distinctive behavior allows the separation of the mass enhancement due to electron-phonon coupling from the measured cyclotron-resonance effective mass and the estimation of the superconducting transition temperatures with the standard BCS formula, which are in qualitative agreement with the observed values.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| α-(ET)2(NH4)Hg(SCN)4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1 | Pressure not reported | unknown |
| κ-(ET)2Cu(NCS)2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 10 | Pressure not reported | unknown |
| (TMTSF)2PF6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 0.9 | 1.2 GPa | unknown |
| κ-(BEDT-TTF)2Cu[N(CN)2]Cl Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 13 | 0.03 GPa | unknown |
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