Npj Comput. Mater.: 轨道耦合—调控谷能带和激子劈裂

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来自清华大学深圳国际研究生院的邹小龙教授研究团队，提出了一种可行的调控方案，通过调控层间轨道杂化来调控能带以及激子的谷劈裂。他们设计构建了由二维室温铁磁VSe₂与MSe₂（M=Mo,W）组成的范德瓦尔斯异质结，通过第一性原理计算方法证实可以通过改变交换相互作用强度、应变或电场来改变MSe₂ 和 VSe₂ 的能谷之间的能级排列，从而调控轨道间杂化。强的轨道杂化引起单层 MSe₂价带中超过30 meV的能谷劈裂和超过 150 meV 的谷激子劈裂。此外，轨道杂化还可以带来谷劈裂符号的改变，为二维过渡金属硫族化合物中谷自由度的调控提供了一种切实有效的方法。

该文近期发表于npj Computational Materials 8：239(2022)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Tunable valley band and exciton splitting by interlayer orbital hybridization

Dan Wang & Xiaolong Zou 

Magnetic proximity effect has been demonstrated to be an effective routine to introduce valley splitting in two-dimensional van der Waals heterostructures. However, the control of its strength and the induced valley splitting remains challenging. In this work, taking heterobilayers combining monolayer MSe2 (M = Mo or W) with room-temperature ferromagnetic VSe2 as examples, we demonstrate that the valley splitting for both band edges and excitons can be modulated by the tuning of the interlayer orbital hybridization, achieved by inclusion of different amounts of exact Hartree exchange potential via hybrid functionals. Besides, we show such tuning of orbital hybridization could be experimentally realized by external strain and electric field. The calculations suggest that large valley band splitting about 30 meV and valley exciton splitting over 150 meV can be induced in monolayer MSe2. Our work reveals a way to control proximity effects and provides some guidance for the design of optoelectronic and valleytronic devices.