Electrons and phonons in C-60-based materials

I have tried to touch on a wide variety of the properties of C60-based materials that are being studied, to convey the breadth of research and give an idea of the degree of understanding of these materials at this time (early 1993). In both the electronic and vibrational aspects, there are many important questions to be resolved. In fact, since relevant electronic and vibrational energy scales (and therefore time scales) appear to be about equal, there is even a question whether many of the properties of fullerides can be interpreted as either “electronic” or “phononic” as is done for conventional metals and superconductors, or whether a hybrid quantity must be considered from the beginning. It is probably of little use to try to summarize which properties are “well understood” and which are “not understood.” A number of properties are rather well characterized from the experimental viewpoint, however, viz. the structural and many of the dynamical properties, and much good data exists in the thermodynamic and spectroscopic areas. This chapter reflects the solid groundwork, both experimental and theoretical. that has emerged, mostly within the last two years. It should be evident that many of the important questions are far from settled. For the superconductivity, for example, a consistent picture in terms of the conventional BCS theory has arisen, except that there is no formal justification for the theory in this class of materials. These materials promise to provide a stimulating area of research for several years to come. © 1994 Academic Press, Inc.