# Berlin 2015 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 57: Optical properties of bulk semiconductors

### HL 57.1: Vortrag

### Mittwoch, 18. März 2015, 16:15–16:30, EW 015

**Quantum defect of the Rydberg series for cuprous oxide** — •Florian Schöne, Heinrich Stolz, and Stefan Scheel — Universität Rostock MNF/IfPH, 18055 Rostock, Germany

The bound-state energies of semiconductor excitons are commonly described by the hydrogenic Rydberg formula *E*_{n}=−*Ry*/*n*^{2}. However, recent experiments in cuprous oxide^{1} have shown that the energy levels for highly excited p-excitons of the yellow series deviate significantly from the established Rydberg formula. Amongst the possible origins of this deviation, such as frequency-dependent background permittivity and coupling to LO-phonons, the largest contributing factor is the nonparabolic shape of the Γ^{7+} valence band. Based on the Suzuki-Hensel-Hamiltonian^{2} which covers spin-orbit and magnetic interactions on symmetry grounds, we are able to analytically describe the nonparabolicity of the valence bands. Applying the concept of quantum defects known from atomic physics, the deviations of the resulting bound-state energies from the hydrogenic Rydberg series can be effectively incorporated in a single parameter δ_{n,l} according to *E*_{n,l}=−*Ry*/(*n*−δ_{n,l})^{2}. We will show the results for the calculation of the first Rydberg-Ritz parameters for the lowest angular-momentum exciton states of the yellow series of *Cu*_{2}*O*.

Kazimierczuk, T. *et al.*, Nature **514**, 343-347 (2014)

Suzuki K., Hensel J. C., Phys. Rev. B **9**,4184 (1974)