Magneto-Stark effect of yellow excitons in cuprous oxide

We investigate and compare experimental and numerical excitonic spectra of the yellow series in cuprous oxide (${\mathrm{Cu}}₂\mathrm{O}$) in the Voigt configuration and thus partially extend the results of F. Schweiner et al. [Phys. Rev. B 95, 035202 (2017)], who considered only the Faraday configuration. The main difference between the configurations is given by an additional effective electric field in the Voigt configuration, caused by the motion of the exciton through the magnetic field. This magneto-Stark effect was already postulated in 1961 by E. F. Gross et al. [Sov. Phys. Solid State 3, 221 (1961)] and D. G. Thomas and J. J. Hopfield [Phys. Rev. 124, 657 (1961)]. Group-theoretical considerations show that, most of all, the field significantly increases the number of allowed lines by decreasing the symmetry of the system. This conclusion is supported by both the experimental and numerical data.