Farenbruch Andreas, Fröhlich Dietmar, Yakovlev Dmitri R, Bayer Manfred
Experimentelle Physik 2, Technische Universität Dortmund, D-44221 Dortmund, Germany.
Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia.
Phys Rev Lett. 2020 Nov 13;125(20):207402. doi: 10.1103/PhysRevLett.125.207402.
We demonstrate the Rydberg series of dark excitons, known as paraexcitons, up to the principal quantum number n=6 for the yellow exciton series in Cu_{2}O, using second harmonic generation. Each of these states is optically inactive to all orders, but their observation becomes possible by application of a magnetic field which leads to mixing with the quadrupole-allowed bright excitons, called orthoexcitons, of the same n. The dark parastates are generally located below the bright orthostates, whose energies are increased by the electron-hole exchange interaction, except for n=2, where this order is reversed. This inversion occurs due to band mixing, namely, of the 2S_{y,o} orthoexciton of the yellow series with the 1S_{g,o} orthoexciton of the green exciton series.
我们利用二次谐波产生，展示了氧化亚铜（Cu₂O）中黄色激子系列直至主量子数n = 6的里德堡暗激子系列，即对激子。这些状态中的每一个在所有阶次下都是光学非活性的，但通过施加磁场使它们与具有相同n的四极允许的亮激子（称为正激子）混合，从而使得对它们的观测成为可能。暗的对态通常位于亮的正态之下，亮正态的能量因电子 - 空穴交换相互作用而增加，但n = 2时除外，此时这种顺序相反。这种反转是由于能带混合，即黄色系列的2S_{y,o}正激子与绿色激子系列的1S_{g,o}正激子之间的混合。
