Landau-level quantization of the yellow excitons in cuprous oxide

Lately, the yellow series of $P$-excitons in cuprous oxide could be resolved up to the principal quantum number $n$ = 25. Adding a magnetic field, leads to additional confinement normal to the field. Thereby, the transition associated with the exciton $n$ is transformed into the transition between the electron and hole Landau levels with quantum number $n$, once the associated magnetic length becomes smaller than the related exciton Bohr radius. The magnetic field of this transition scales roughly as $n^{-3}$. As a consequence of the extended exciton series, we are able to observe Landau level transitions with unprecedented high quantum numbers of more than 75.