The main objective of this action was to provide an essential contribution to knowledge and development in the various fields of strongly correlated electron systems via a concerted European effort. Basic research in this area required the co-operation of a large number of scientists from various fields.
The aim was to study experimentally as well as theoretically correlated systems which possess complex interactions between many degrees of freedom, in order to find new phases of matter. On the experimental side a strong effort in the production of high-quality materials and samples will be the fundament of successful studies. These include mainly d- and f electron systems, intermetallic and oxide compounds in various forms, polycrystalline and single crystals as required, amorphous or in artificially layered structures. Studies of materials in diverse forms gave a new insight on different quantum phases, on order-disorder phenomena, on the issue of effective dimensionality as a function of various external parameters, such as temperature, pressure or doping. The understanding of the complex phase diagrams and the underlying physic of strongly correlated electron systems is the basis for future applications in electronic devices and sensors or large-scale facilities as electric power transmission and control.
A larger number of challenges had to be coped with. These included the identification of order parameters and pairing mechanisms of unconventional superconductors in the growing number of newly discovered superconducting strongly correlated electron systems. A further important task to be tackled was concerned with the distinction between the two major theoretical scenarios describing the physics in the proximity of a quantum critical point: the Hertz-Mills-Moriya theory and the composite-electron theories based on fractionalization of electronic degrees of freedom. This implied in addition a clear characterization of the non-Fermi-liquid behaviour which provides insights into one important aspect of quantum criticality.
A number of diverse experimental techniques were employed in this endeavour, various spectroscopic techniques, such us neutron scattering (including spectroscopy of magnetic and lattice excitations), tunnelling spectroscopy, muon-spin-resonances measurements or various optical measurements. Transport and thermodynamic measurements, such as resistivity, Hall effect, heat transport, thermoelectric effects or specific heat and thermal expansion represent further ways to probe the physical behaviour of materials. The great advantage of a large scale collaboration of this kind, was the opportunity to exchange samples which have been characterized and measured by various techniques and so avoiding wrong conclusions due to sample variety which is often unavoidable in forefront basic material science.
Finally the activities of the Action included the exchange and the training of graduate students and postdoctoral fellows.
Overall the goal of ECOM was to maintain and enhance further the leading role the European science community plays in this rapidly developing field of strongly correlated electron systems and to ensure that European research group remains competitive with the USA and Japan.