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The frontier of modern solid state physics lies in understanding the electronic properties of those complex systems in which the valence electrons self-organize into novel ground states substantially different from those of conventional metals and insulators. Strong electron-electron correlations, in concert with electron-phonon interactions, can give rise to a large variety of fascinating phenomena, the most spectacular being probably Mott-Hubbard insulating behaviour, unconventional and high-temperature superconductivity, and colossal magneto-resistance. In addition, by lowering the system dimensions (from 3D bulk, over 2D thin films, to 1D nanostructures) the physical properties can change dramatically, which could lead to new concepts, materials, and technological advances. On the fundamental side, the aim is to understand the underlying microscopic mechanisms responsible for the physical properties of these systems. On the more applied side, the goal is to learn how to actively control those mechanisms and to define alternative pathways for the design of new materials and functional devices. In this context, in addition to the more traditional work performed on high-quality single crystals, the growth of thin films on crystalline substrates and the fabrication of molecular nanostructures, with molecular beam epitaxy methods and/or atomic manipulation techniques, will provide exciting and qualitatively new research opportunities. In fact, these methods will allow the production of systems that can not be obtained through the more conventional synthesis processes. To address the appropriateness of the current approaches in the quantum theory of solids and for the development of suitable microscopic models, it is necessary to investigate the elementary excitations of these novel complex systems, as they reflect the interplay between the low-energy degrees of freedom and determine macroscopic physical properties such as electrical resistivity, magnetic susceptibility and specific heat. The research activity of the group will then focus on the study of novel complex systems by ARPES and other electron spectroscopy techniques. Specific research projects will include: 1. Orbital
excitations in orbital-ordered ferromagnets
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