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Next: Experiments on CsBi-GIC's Up: Hydrogenation Experiments on Previous: Possible Explanations for



The hydrogen-induced Tc enhancement that occurs in C4KHg is a dramatic, reproducible phenomenon. Hydrogenation data looks much like that from experiments with applied pressure, so it is believed that these effects have a common origin. The charge-density wave explanation of the difference between the pink and gold samples also seems consistent with the hydrogenation and pressure experiments. Other explanations, such as a disorder-order transition, or a structural phase transition, are not consistent with the all the available data.

Since there is no direct experimental evidence for a CDW in C4KHg, there are many experimental tests that should still be performed. Temperature-dependent electron microscopy and transport measurements (chi(T) and rho(T)) have already been mentioned. Other possibilities are specific heat experiments to directly measure N(0) and Lambdaep, and NMR or ESR measurements to try to learn more about the chemical state of the absorbed hydrogen. In addition, studies of Tc as a function of H pressure are desirable. Some of these measurements may be carried out with existing well-characterized samples by Prof. T. Enoki of the Tokyo Institute of Technology. No doubt more surprises are in store.

Like the KHg-GIC's, the CsBi-GIC's have several in-plane phases. The existence of superconductivity in the CsBi-GIC's has been controversial due to reproducibility problems.[145] The various Tc's and multiple phases of the CsBi-GIC's are obviously of great interest for comparison with the results described in this chapter. (Alison Chaiken)
Wed Oct 11 22:59:57 PDT 1995