Rydberg excitons in the many-particle system solid

• Applicant: Dr. Dirk Semkat
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 400970559

The first observation of excitons with main quantum numbers of n>20 in cuprous oxide has initiated a new and rapidly growing research area of semiconductor physics: the physics of Rydberg excitons. The observation of the Rydberg blockade, where the presence of an exciton prevents the excitation of further excitons due to dipole-dipole interactions, well-known in the physics of Rydberg atoms, has played an important role.The success in the interpretation of the experimental results obtained so far has relied on the application of atomic concepts. However, these concepts fail if the influence of the surrounding solid state becomes dominant and have to be modified.Such influences of the surrounding medium are, e.g., the interactions with phonons, photons, impurities or defects, and, in particular, with an electron-hole plasma. From first results one can expect a strong influence on the Rydberg excitons which, e.g., manifests itself in a systematic decrease of the strength of the absorption lines with increasing plasma density (plasma blockade). Due to the Auger effect where two excitons decay into an electron-hole pair, in cuprous oxide, any optical excitation of excitons unavoidably leads to the presence of an electron-hole plasma giving rise to additional blockade effects.The central goals of the project are the many-particle theoretical foundation of the plasma effect, the investigation of the blockade mechanisms, and the experimental clarification of the plasma relaxation dynamics.

• DFG Programme: Research Grants