The electronic structure of strongly correlated electron systems

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Strongly correlated electron systems exhibit some of the most interesting physical properties for possible future applications in electronic devices, sustainable energy, biomedical devices, transportation and perhaps even quantum computing. Materials made of transition metal and rare earth compounds such as the oxides are examples often exhibiting extreme properties such as high temperature superconductivity, high thermoelectric power, high dielectric constants, collassal magneto resistance and many more. These materials are different from conventional semiconductors like Si or simple metals like Al in which the charge of the electrons moving in amongst atoms plays the important role in determining the applications. Transition metal oxides on the other hand often are electrical insulators and magnetic because of the strong repulsive interaction between the electrons. However chemical substitution can turn such magnetic insulators into high temperature superconductors ( Nobel Prize 1988 ) and cause other dramatic changes in their properties. The basic physics governing their behaviour remains one of the biggest intellectual challenges of modern scientific research. Here the spin and orbital degrees of freedom and their interplay with the charge degrees of freedom of electrons play essential roles. New experimental methods are needed which are sensitive to these degrees of freedom and applicable to nanometer scale structures such as in thin films, interfaces and heterostructures.