Fine Structure of Rydberg Excitons in Cuprous Oxide

In 1952, E.F. Gross and N.A. Karryev discovered excitons of big radius also called the Wannier-Mott excitons. Their energy spectrum, response to external electric and magnetic fields, and also elastic deformations of a crystal were extensively studied in the 1960s-1970s. The second wave of interest to excitons in Cu2O crystals appeared comparatively recent, in 2014, after the "giant" highly excited exciton states had been observed in this material. A theoretical description of highly excited exciton states needs, as a rule, new approaches, because, for such states, a deviation from the exactly solved hydrogen-like model becomes substantial and a numerical solution of the Schrodinger equation with allowance made for the features of the crystal energy band structure becomes extremely resource consuming. This report is a brief review of recent theoretical and experimental studies of the fine structure of the exciton energy spectrum in copper protoxide.