Bipolaron and Multipolaron States in Magnetic Fields

• Applicant: Professor Dr. Marcel Griesemer
• Subject Area: Mathematics
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 209234201

The interaction of electrons of a polar crystal with quantized lattice vibrations (phonons) leads to bound states of electrons and phonons, so called polarons. The electron-phonon interaction,moreover, mediates an attractive force between pairs of polarons which competes with theCoulomb repulsion. Whether or not this attraction will dominate the repulsion, depends on the values of the parameters of the crystal. In the physically important and non-perturbative regime of strong electron-phonon coupling it is well-understood, within the Fröhlich polaron model, that the attraction may be strong enough to produce bound states of polarons, called bipolarons. It is also clear that bipolarons are a phenomenon due to quantum mechanical correlations, as the electrostatic forces between electrons in the solid are always predominantly repulsive. This project is devoted to the questions whether bound states of more than two polarons may exist and whether or not an external magnetic field enhances the binding of polarons, as suggested by the physics literature. In addition to the physical relevance of these questions, the proposed project draws its large significance from the importance of the Fröhlich polaron model as a standard model of non-relativistic quantum field theory.

• DFG Programme: Research Grants