Mo{sub 6}Se{sub 8}-cluster-based superconducting compounds Cs{sub 2}Mo{sub 12}Se{sub 14} and Rb{sub 4}Mo{sub 18}Se{sub 20}: Evidence for a strongly correlated and anisotropic electron system
- Centre de Recherches sur les Tres Basses Temperatures, Laboratoire associe a l`Universite Joseph Fourier, CNRS, Boite Postale 166, 38042 Grenoble-Cedex 9 (France)
- Laboratoire de Cryophysique, Centre d`Etudes Nucleaires de Grenoble, Boite Postale 85 X, 38042 Grenoble-Cedex (France)
- Laboratoire de Chimie Minerale B, Universite de Rennes, Avenue du General Leclerc, 35042 Rennes-Cedex (France)
We studied the normal and superconducting states of the title compounds by measuring the conductivity and magnetization of single crystals and powder samples. From the upper and lower critical fields we deduced the characteristic lengths and thermodynamical fields. These results are borne out by our specific-heat measurements. We recognize in these compounds many features of the Chevrel-phase superconductors, including very small coherence lengths and strong-coupling-like effects. However, we show that the electron system is much more anisotropic and still less delocalized in these materials where the Mo{sub 6}Se{sub 8} clusters have condensed in Mo{sub 6{ital n}}Se{sub 6{ital n}+2} finite chains. This condensation is accompanied by an enhancement of the magnetic response whereas the lengthening of the chains leads to a counteracting reduction of the density of carriers. This indicates that superconductivity is built upon highly correlated molecular states. Reviewing the available data on the other Chevrel-cluster-based superconductors confirms this picture and suggests that the small coherence lengths reflect the local character of the electron pairing. This comparison also shows that forming finite chains of Mo{sub 6}Se{sub 8} clusters makes the electron correlations more repulsive and pushes the electron system near the borderline between superconductivity and magnetism. In this respect these compounds could provide valuable complementary information on issues which are at the center of the research upon high-{ital Y}{sub {ital c}} superconductivity.
- OSTI ID:
- 90508
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 6; Other Information: PBD: 1 Aug 1995
- Country of Publication:
- United States
- Language:
- English
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