Continuous Metal-Insulator Transitions in Highly Correlated Systems

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9801824 Rosenbaum In this research conducted by Prof. Th. A. Rosenbaum of the James Franck Institute of the University of Chicago the problem of metal-insulator (MI) transitions resulting from continuous changes in external parameters will be experimentally investigated. Specifically, the continuous Mott-Hubbard transition in NiS(2-x)Sex, the MI transition in metal hydride films, and the MI transition in vanadium sesquioxide in the highly disordered limit will be studied. These researches have important bearing on the properties of novel materials, such as transition metal oxides and sulfides, high-Tc superconducting cuprates, giant magnetoresistance manganates, and others that are governed by strong charge carrier correlations. The purpose of this research is to elucidate the fundamental nature of the MI transition in materials where electron-electron interactions dominate and where it is possible to apply the experience obtained from studies of continuous phase transitions. %%% Many materials of current technological importance, such as, for example, transition metal oxides and sulfides, metal hydrides, high-temperature superconducting cuprates, colossal magnetoresistance manganates, exhibit behaviors that are not yet fully understood. This absence of detailed understanding impedes their efficient application in technological devices. Among these properties is the continuous change of a material from a metal to an insulator (MI) in systems in which the behavior of the electric charge carriers is highly correlated. For example, at liquid helium temperatures the electrical conductivities of materials can vary by 32 orders of magnitude. It was only during the last year that materials systems were discovered (doped semiconductors and amorphous alloys) in which the MI transition proceeds in a continuous manner in response to the variations of an external parameter. The purpose of this research is to elucidate the fundamental nature of the MI transition in materials where electron-electron interactions dominate and where it is possible to apply the experience obtained from continuous phase transitions. The results of these investigations will be of great importance for the development and application of new and improved electronic solid state materials. ***