Riesen magneto-photoelektrischer Effekt in Graphen

• Antragsteller: Dr. Friedemann Queisser
• Fachliche Zuordnung: Theoretische Physik der kondensierten Materie
• Förderung: Förderung von 2018 bis 2023
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 398912239

• Erstellungsjahr: 2021

Zusammenfassung der Projektergebnisse

Within the project, the primary and secondary particle-hole generation at graphene edges which are subject to a magnetic field has been investigated. The research indicated that carrier multiplication at graphene edges is a rather robust effect and independent on the particular edge geometry. Since the effective fine structure constant of graphene exceeds unity, a hierarchical expansion method for general strongly interacting lattice systems has been developed further. It allowed the derivation of Boltzmann equations for strongly interacting lattice systems and was applied to a bipartite lattice model with strong Coulomb interaction and to the strongly interacting fermionic Hubbard model. Using this approach, also the derivation of Boltzmann equations which contain Auger processes such as impact ionization and pair annihilation seems to be feasible in future work. Furthermore, the hierarchy of correlations was extended to dissipative lattice models which would also allow the study of the environmental influence onto particle-hole excitations in the presence of strong interactions. The tunneling rates of electrons in solids and thus the effective fermi velocity can be altered by external time-dependencies. This is a consequence of adiabatic and non-adiabatic changes of the tunneling rates. In order to understand the modification of tunneling amplitudes from first principles, the impact of an external time-dependent electrical field on the tunneling through a Box potential and the triangular potential was investigated. Although simple analytical solutions could not be obtained for periodic lattice potentials, the main effects which have been identified are likely to be present also in lattice systems. An explicit time-dependence of hopping rates influences the dynamics of correlation functions in lattice models. This motivated the extension of the hierarchy of correlations to double-time Green functions and the study of the light-cone structure of correlation functions.

Projektbezogene Publikationen (Auswahl)

• Optical absorption and carrier multiplication at graphene edges in a magnetic field
  F. Queisser, S. Lang and R. Schützhold
  
• Boltzmann relaxation dynamics in the strongly interacting Fermi-Hubbard model, Phys. Rev. A 100, 053617 (2019)
  F. Queisser and R. Schützhold
  
• Boltzmann relaxation dynamics of strongly interacting spinless fermions on a lattice, Phys. Rev. B 100, 245110 (2019)
  F. Queisser, S. Schreiber, P. Kratzer, and R. Schützhold
  
• Dynamically assisted tunneling in the impulse regime, Phys. Rev. Research 3, 033153 (2021)
  C. Kohlfürst, F. Queisser and R. Schützhold