The main aspects of physical phenomena associated with the optical orientation of the spin and valley degrees of freedom in transition metal dichalcogenide monolayers and in van der Waals heterostructures based on them have been briefly reviewed. Owing to features of the band structure and spin–orbit coupling in such systems, circularly polarized light induces optical transitions in different valleys K₊ and K_– of the Brillouin zone; consequently, the optical orientation of charge carriers and excitons is accompanied by their valley polarization. The main features of the band structure of transition metal dichalcogenide monolayers, excitonic effects, and results of theoretical studies of the valley orientation of excitons and electrons at one-photon absorption have been reported. The linear–circular dichroism and valley orientation of free charge carriers and excitons at multiphoton absorption have been studied. Effects associated with the trigonal symmetry of monolayers, including the inversion of valley polarization at two-photon transitions and the second harmonic generation, have been discussed. The considered theoretical models have been illustrated by experimental data.

简要回顾了与过渡金属二卤化硅单分子层和基于它们的范德华异质结构中自旋和谷自由度的光学取向相关的物理现象的主要方面。由于这种系统的能带结构和自旋轨道耦合的特性，圆偏振光会在不同的波谷K ₊和K _–内引起光学跃迁。在布里渊区；因此，电荷载流子和激子的光学取向伴随着它们的谷极化。已经报道了过渡金属二硫化氢单层的能带结构的主要特征，激子效应以及在单光子吸收时激子和电子的谷取向的理论研究结果。研究了自由电荷载流子和激子在多光子吸收下的线性-圆二向色性和谷取向。已经讨论了与单层三角对称有关的效应，包括在两个光子跃迁处的谷极化反转和二次谐波的产生。实验数据已经说明了所考虑的理论模型。