The spectacular physical properties often observed in materials containing transition metal and rare-earth elements challenge our comprehension of solid state physics These properties include superconductivity, unusually large magneto-resistance, metal-insulator transitions, heavy-fermion behaviour, multiferroicity, and phenomena involving topologically protected states. We would like to understand how the electrons in such materials interact with each other as to generate those unusual quantum phenomena. From a theoretical viewpoint it turns out that the equations we have to solve are so complicated that we will not be able to obtain exact solutions. To make things worse and more fascinating at the same time, tiny changes in temperature, pressure or in the material composition may cause large changes of the properties, so that it appears that there are many solutions available that are lying very close together in energy.
With exact solutions out of reach, the objective of our ‘Physics of Correlated Matter’ department is to find smart approximations by which we can capture the essential ‘physics’ to describe the ‘correlated’ motion of the electrons in such materials. It may very well be that we need to develop and use different approximations for different materials or properties. In order to probe these materials and properties the research activities of our department are focussed on the investigation of the electronic structure of the materials, using both spectroscopic tools as well as material specific many body calculations. This combined experimental and theoretical work is essential to identify the most suited approximation. The experimental activities have also a strong material development component: new materials, both in bulk as well as in thin film form, are synthesized in order to tune the relative strength of the relevant interactions. Guided by the smart approximations developed, we aim to optimize the properties for applications and we hope to even discover new phenomena.