next up previous contents
Next: The Quest for Up: Experiments on CsBi-GIC's Previous: Experiments on CsBi-GIC's


  Several unresolved questions pertinent to the superconductivity of the KHg-GIC's have been discussed at length in previous chapters. Among the most intriguing of these is why C8KHg has a higher Tc than C4KHg, how the superconducting properties of the various phases of C4KHg differ, and whether two-dimensional superconductivity can be observed in GIC's. These questions are difficult to approach on a first-principles basis because of the large unit cell and complex band structure of the ternary compounds. As a result, much of the current understanding has been derived from qualitative comparisons of ternary GIC data with that from different materials, principally the binary GIC's and TMDC's discussed in Chapter gif .

When Lagrange and his colleagues at the University of Nancy announced the synthesis of the MBi-BIC's (M = K, Rb, or Cs) in 1985,[146], they opened up a whole new arena for the exploration of these issues. The new ternary GIC's were not only reported to be superconducting, but they also possessed many of the more unusual features of the KHg-GIC's. Specifically, Lagrange et al. said that the CsBi-GIC's show a higher Tc for stage II than stage I, the same surprising stage dependence that is exhibited by the MHg-GIC's.[167] Secondly, for each alkali metal and each stage they reported two different phases of the MBi-GIC's, with the phases distinguished by different sandwich thicknesses.[146,167] These phases were said to have different superconducting transition temperatures,[167] perhaps similar to the situation in the KHg-GIC's [see Chapter gif ]. The announcement of the MBi-GIC's also gave new life to the search for two-dimensional superconductivity in GIC's since the rubidium compounds could be prepared in stages up to seven.[146]

The discovery of the MBi-GIC's spurred a great deal of experimental activity, in large part because of the high Tc of about 4 K[146] reported for the CsBi alpha-phase material. The results of further studies on the superconductivity of these materials are reported below.

next up previous contents
Next: The Quest for Up: Experiments on CsBi-GIC's Previous: Experiments on CsBi-GIC's (Alison Chaiken)
Wed Oct 11 22:59:57 PDT 1995