Dipole-allowed generation of the yellow-series excitons in Cu2O due to an applied electric field -: art. no. 235101

The electron bands of Cu2O near the band gap have been calculated for the undistorted cubic crystal with O-h symmetry and a tetragonally distorted case with C-4v symmetry. The tetragonal structure has a distortion of the linear Cu crystal field that represents the structure of a polarized crystal in an electric field. The symmetry of the bands changes in such a way that the dipole forbidden transition of the yellow series excitons in the undistorted cubic structure becomes dipole allowed in the tetragonal structure. The energy of the excitons becomes lower in the polarized crystal. These changes in the band gap properties make it possible to create an exciton trap in thin Cu2O films with a scanning tunneling microscopy tip while the excitons can be resonantly created with a laser via a dipole allowed transition.