Colloquium: Excitons in atomically thin transition metal dichalcogenides
Colloquium: Excitons in atomically thin transition metal dichalcogenides
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DOI：
10.1103/revmodphys.90.021001
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发表时间：
2018-04-04
影响因子：
44.1
通讯作者：
Urbaszek, Bernhard
中科院分区：
文献类型：
--
作者：
Wang, Gang;Chernikov, Alexey;Urbaszek, Bernhard
原子薄的材料，如石墨烯和单层过渡金属二硫属化物（TMD）表现出显着的物理性质，这是由于它们的降维和晶体对称性。半导体过渡金属二硫属化物的家庭是一个特别有前途的平台，二维（2D）系统的基础研究，在光电子学和谷电子学由于其直接带隙在单层极限和高效的光-物质耦合的潜在应用。具有破缺的反转对称性的晶格结合强自旋-轨道相互作用导致自旋和谷自由度的独特组合。此外，2D字符的单分子膜和弱介电屏蔽的环境产生显着增强的库仑相互作用。由此形成的束缚电子-空穴对或激子主导了材料的光学和自旋性质。本文回顾了单层TMD激子性质研究的最新进展，并展望了未来的挑战。讨论了强的直接库仑相互作用和交换库仑相互作用、激子光-物质耦合以及有限载流子和电子-空穴对密度对TMD中激子性质的影响。最后，谷极化的影响进行了描述和调谐的能量和极化观察到的电场和磁场进行了总结。
Atomically thin materials such as graphene and monolayer transition metal dichalcogenides (TMDs) exhibit remarkable physical properties resulting from their reduced dimensionality and crystal symmetry. The family of semiconducting transition metal dichalcogenides is an especially promising platform for fundamental studies of two-dimensional (2D) systems, with potential applications in optoelectronics and valleytronics due to their direct band gap in the monolayer limit and highly efficient light-matter coupling. A crystal lattice with broken inversion symmetry combined with strong spin-orbit interactions leads to a unique combination of the spin and valley degrees of freedom. In addition, the 2D character of the monolayers and weak dielectric screening from the environment yield a significant enhancement of the Coulomb interaction. The resulting formation of bound electron-hole pairs, or excitons, dominates the optical and spin properties of the material. Here recent progress in understanding of the excitonic properties in monolayer TMDs is reviewed and future challenges are laid out. Discussed are the consequences of the strong direct and exchange Coulomb interaction, exciton light-matter coupling, and influence of finite carrier and electron-hole pair densities on the exciton properties in TMDs. Finally, the impact on valley polarization is described and the tuning of the energies and polarization observed in applied electric and magnetic fields is summarized.