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  • Quantum and quasi-classical magneto-oscillations of electron system in low dimensional organic metals and superconductors studied by means of galvanomagnetic, thermal, and magneto-optical measurements

Quantum and quasi-classical magneto-oscillations of electron system in low dimensional organic metals and superconductors studied by means of galvanomagnetic, thermal, and magneto-optical measurements

GPI: The frequency response of the cyclotron resonance peak of (BEDO-TTF)2ReO4*H2O suggest strong Fermi-liquid renormalisation effects in the 2D charge carriers. Phonon drag effects control the thermoelectric powers of alpha-(ET)2MHg(SCN)4, kapa-(ET)2Cu(SCN)2 and (ET)3Cl2*H2O, despite their respective different temperature behaviour. Renormalizations of the g-factor are suggested in order to describe the anomalous temperature dependence, in strong magnetic field, of the quantum oscillations in alpha-(ET)2MHg(SCN)4 with M + K, Tl.

ISSP: For the first time, plateau-like features reminiscent of the quantum Hall effect, are evidenced in high quality bulk crystals of alpha-(ET)2TlHg(SCN)4. Specific heat measurements performed on kappa-(ET)2KHg(SCN)4 indicate that:
i. the "10 K resistivity hump", which signs the SDW condensation, is suppressed by increasing applied magnetic fields, and
ii. this suppression is shown to be anisotropic.
Analysis of the pressure-dependent SdH oscillations of kappa-(ET)2Cu(N(CN)2)Br yields a model of its Fermi surface which takes into account the reported superstructural transition and explains the difference between this salt and other kappa-type superconductors. (BETS)2C(CN)3 is the first radical cation salt to display the kappa-type donor arrangement with a planar-triangular discrete anion. The lack of superconducting ground state can be assigned to disorder in the positions of the ethylenedithio groups of the BETS molecules. The strong contribution to the linear combination of SdH-like frequencies, which are observed in fields lower than 14 T, suggests quantum interference effects.

ICP: An original method for measuring the anisotropy of resistivity has been applied to vita-ET)2((IBr2)0.7(I3)0.3) single crystals. This salt displays around 130 K, an order-disorder phase transition, which has been studied by a differential scanning calorimetric technique. ICP has provided high quality single crystals of the organic (super)conductors mentioned above. Furthermore, the following novel molecular metals, with promising new electron properties, have been synthesized:
i. the alpha-phase of (ET)2TlHg(Se1-xSxCN)4, the Pd(dddt)2 cation complex, the kappa-phases of,
ii. (ET)2X with X = Cu(N(CN)2)Br1-xClx, and iv) (BETS)2Y with Y = Bi2Cl8. Also, conducting polymeric films, homogeneously doped with (ET)2I3, are shown to display uniquely superconducting properties.

Reported by

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
TOULOUSE
France
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