Twist Angle-Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures
Twist Angle-Dependent Interlayer Exciton Lifetimes in van der Waals Heterostructures
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DOI：
10.1103/physrevlett.126.047401
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发表时间：
2021-01-26
影响因子：
8.6
通讯作者：
Li, Xiaoqin
中科院分区：
文献类型：
--
作者：
Choi, Junho;Florian, Matthias;Li, Xiaoqin
在范德华(VDW)异质结构中，由两层过渡金属二卤化物堆积而成，形成了具有高度可调谐性质的多激子共振，并受到垂直和横向的限制。我们研究了如何使用一个独特的控制旋钮，即两个单分子膜之间的扭角来控制激子动力学。我们观察到当扭转角度从1度变化到3.5度时，MoSe_2/WSe_2扭转双层膜(TBL)中的层间激子寿命发生了一个数量级的变化。利用低能连续介质模型，我们从理论上分离了影响层间激子辐射寿命的两种主要机制。随着扭角的增加，动量空间向间接跃迁的转变以及MoIL 6势的能量调制都对层间激子寿命有显著的影响。我们进一步预测了不同扭角的TBL中层间激子寿命随温度的变化规律，并通过实验进行了部分验证。虽然最近的许多研究强调了如何利用VDW TBL中的扭曲角来设计由于多体相互作用而产生的基态和量子相，但我们的研究探索了它在控制光学激发态动力学中的作用，从而扩展了扭曲电子学的概念应用。
In van der Waals (vdW) heterostructures formed by stacking two monolayers of transition metal dichalcogenides, multiple exciton resonances with highly tunable properties are formed and subject to both vertical and lateral confinement. We investigate how a unique control knob, the twist angle between the two monolayers, can be used to control the exciton dynamics. We observe that the interlayer exciton lifetimes in MoSe2/WSe2 twisted bilayers (TBLs) change by one order of magnitude when the twist angle is varied from 1 degrees to 3.5 degrees. Using a low-energy continuum model, we theoretically separate two leading mechanisms that influence interlayer exciton radiative lifetimes. The shift to indirect transitions in the momentum space with an increasing twist angle and the energy modulation from the moil 6 potential both have a significant impact on interlayer exciton lifetimes. We further predict distinct temperature dependence of interlayer exciton lifetimes in TBLs with different twist angles, which is partially validated by experiments. While many recent studies have highlighted how the twist angle in a vdW TBL can be used to engineer the ground states and quantum phases due to many-body interaction, our studies explore its role in controlling the dynamics of optically excited states, thus, expanding the conceptual applications of "twistronics".