The main objective of this action is 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 requires the co-operation of a large number of
scientists from various fields.
Our aim is 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 felectron
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 are expected to shed new light 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 have to be coped with. These include 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 is 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 implies in addition a clear characterization of the non-
Fermi-liquid behaviour which provide insights into one important aspect of quantum
criticality.
A number of diverse experimental techniques will be 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 largescale
collaboration of this kind, is 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.
The role of the theory part besides accompanying the experimental efforts, lies in the
development of new tools and concepts to address the important fundamental questions. The
break-down of the standard Fermi liquid model in many strongly correlated electron systems
has since many years posed one of the biggest challenges in the theoretical physics. Concepts
concerning quantum phase transitions have to be extended, as several recent experimental
results suggest. Beyond this there are many open questions concerning the quantum phases
themselves, in particular, quantum liquids of various kinds of degrees of freedom which
represent the basic fundament (“vacuum”) on which new physical phenomena appear.
Theorists have also the task to propose new tests for theoretical concepts. ECOM involves
many groups with well spread expertise so that different viewpoints may melt together to
fruitful novel concepts.
A further important aspect of ECOM is the fact, that many Eastern European teams
will be involved, providing access to the strong expertise in these countries and at the
same time integrating them into the greater European effort in this field. Many of these
Eastern European research groups are actually relying on support via program to have
a contact to Western European labs.
Finally also the educational aspect has be kept in mind, as activity of the Action will
include the exchange and the training of graduate students and postdoctoral fellows.
Overall the goal of ECOM is 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 remain competitive with the USA and
Japan..
