Investigation of exciton fine structure inCu2O

Abstract

The even-parity excitons in ${\mathrm{Cu}}_2$O show, in contrast to the well known $P$-exciton series: (1) strong deviations from a hydrogenlike behavior, (2) a fine structure for $n\ge 3$, and (3) an unusual $n$ dependence of the exchange splitting. All the properties of the even-parity-exciton series are explained by the presence of a strong $H_d$ term and a strong exchange interaction. We have calculated the even- and odd-exciton members of the yellow and green series within the formalism of Baldereschi and Lipari. An excellent agreement with the experimental results is obtained in the spherical limit. The theory predicts for $n=3\mathrm{}$ a splitting of the $S$ and $D$ states into five components. All the five components are observed by two-photon absorption in a magnetic field of 7 T.