Fachbereich 13




The group is engaged in the investigation of anomalous properties of condensed matter systems where the electron-electron interactions (correlations) are strong.

When electrons strongly interact, their motion is governed by the requirement to minimize their mutual interaction (the Coulomb repulsion), rather than their kinetic energy. As a result, the electrons’collective behavior can be quite distinct from what is known from simple metals, where electron interactions can be safely neglected. Phenomena originating in strong electronic correlations are, for instance, heavy fermions, novel types of superconductivity, Mott-insulating states, anomalous metals, colossal magnetoresistance, or spin liquids.

Our group is dealing with the following projects:

  • Anomalous metallic and superconducting states evolving out of a Mott insulator with particular attention paid to the role of antiferromagnetic order, frustrating magnetic interactions, dimensionality and the coupling to the lattice degrees of freedom.

  • The properties of a non-magnetic, possibly spin-liquid Mott insulator and the character of the nearby metallic/superconducting states.

  • The collective behavior of strongly correlated electrons in novel (mainly organic) materials with variable dimensionality and band-fillings.

  • Properties of low-dimensional quantum spin systems with special emphasis placed on the role of frustrating interactions, the behavior at magnetic field- or pressure-induced quantum critical points.

  • Bose-Einstein condensation and localization of magnetic excitations (magnons) in coupled-dimer systems under variation of physical and chemical parameters.  

The materials of choice are metal organic compounds containing at least one organic component. On the metallic side, these are the so-called organic charge-transfer salt where a stable organic molecule (such as BEDT-TTF) is combined with a suitable inorganic acceptor complex.

For the quantum spin system, transition metal ions with incomplete d-shells or stable organic radicals are used as functional units. These magnetic building blocks are bridged by various, mainly organic linkers to form extended interacting magnetic systems. All systems share a high degree of flexibility enabling their properties to be tuned by variation of chemical and physical parameters.



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Druckversion: 19. Februar 2014, 13:17