Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany.
Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia.
Phys Rev Lett. 2013 Mar 15;110(11):116402. doi: 10.1103/PhysRevLett.110.116402. Epub 2013 Mar 12.
The magneto-Stark effect of excitons is demonstrated to be an efficient source of optical nonlinearity in hexagonal ZnO. Strong resonant second harmonic generation signals induced by an external magnetic field are observed in the spectral range of 2s and 2p excitons. The microscopic theoretical analysis shows that for excitons with a finite wave vector, exciton states of opposite parity are mixed by an effective odd parity electric field induced by the magnetic field despite its even parity. The field, spectral, and polarization dependencies of the second harmonic generation intensity validate the proposed mechanism. The observed phenomenon is not limited to a certain symmetry class and therefore must be effective in other semiconductors.
激子的磁斯塔克效应被证明是六方 ZnO 中光学非线性的有效来源。在外磁场的作用下，在 2s 和 2p 激子的光谱范围内观察到强烈的共振二次谐波产生信号。微观理论分析表明，对于具有有限波矢的激子，尽管磁场具有偶宇称，但由磁场引起的有效奇宇称电场会混合激子的奇偶宇称态。二次谐波产生强度的场、谱和偏振依赖性验证了所提出的机制。观察到的现象不仅限于某一对称类，因此在其他半导体中也必须有效。
