Microscopic description of central-cell corrections for few-exciton systems and the implications for exciton condensation

• Applicant: Dr. Andreas Alvermann
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 147601118

Excitons, which are bound electron-hole pairs, are important elementary excitations of semiconductors. The research project studies excitons, whose radius has the same order of magnitude as the lattice constant, from a theoretical point of view. While such excitons resemble Mott-Wannier excitons, significant differences occur to the hydrogen-like behaviour that persists at large radius. For a coherent description of their properties one must go beyond continuum approximations and account for the changes of electron-hole dispersion and short-range interaction that arise from the presence of the crystal lattice.Modern numerical techniques of quantum physics allow for the study of excitons, bound exciton-exciton states (biexcitons) and exciton-exciton interaction with full inclusion of central-cell corrections. They are based on the combination of adaptive variational basis constructions with advanced algorithms from numerical linear algebra. This enables the computation of static and dynamical properties of general few-particle systems on the lattice and in the continuum.The investigations are motivated by current experiments on Bose-Einstein condensation of excitons in the cuprous oxide. The research project deals with both aspects of a theoretical description of the experiment: The microscopic study of excitons and biexcitons provides fundamental quantities which are used, in a second step, in the macroscopic description of the exciton condensate in the framework of the Hartree-Fock-Bogoliubov theory.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. Peter Littlewood