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HL: Halbleiterphysik

HL 56: Optische Eigenschaften

HL 56.5: Vortrag

Freitag, 28. März 2003, 12:45–13:00, POT/81

K-dependent Exchange Interaction of quadrupolar Excitons in Cu₂O — •G. Dasbach¹, D. Fröhlich¹, H. Stolz², R. Klieber¹, D. Suter¹, and M. Bayer¹ — ¹Institut für Physik, Universität Dortmund, D-44221 Dortmund, Germany — ²Universität Rostock, Fachbereich Physik, D-18051Rostock, Germany

A prototype material for the study of excitons is Cu₂O. Especially the quadrupole allowed lowest yellow exciton state has always attracted interest. This state is investigated with ultra-high spectral resolution, provided by a tunable single frequency laser. As the excitation energy is scanned across the exciton resonance the transmitted intensity is monitored (T_sample = 1.4 K). The experiments show a splitting of this exciton line into a triplet. So far this line was assumed to be threefold degenerate in the absence of external perturbations. Further, this splitting crucially depends on the orientation of the crystal relative to the propagation of the laser beam. However, the resonances remain extremely narrow (sub µeV) even in crystals of few mm thickness, while the splittings are in the order of few µeV. Theses observations exclude an interpretation in terms of strain induced effects. The findings are explained by K-dependent electron-hole exchange interaction, which is treated by the method of invariants up to the order of K².