Quantifying van der Waals Interactions in Layered Transition Metal Dichalcogenides from Pressure-Enhanced Valence Band Splitting
Quantifying van der Waals Interactions in Layered Transition Metal Dichalcogenides from Pressure-Enhanced Valence Band Splitting
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DOI：
10.1021/acs.nanolett.7b02159
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发表时间：
2017-08-01
期刊：
影响因子：
10.8
通讯作者：
Wu, Junqiao
中科院分区：
文献类型：
--
作者：
Ci, Penghong;Chen, Yabin;Wu, Junqiao
货车德瓦耳斯力（vdW）尽管相对较弱，但在过渡金属二硫属化物（TMD）中将层保持在一起，并且在它们的能带结构演化中起关键作用，因此深刻地影响它们的物理性质。在这项工作中，我们通过测量金刚石压砧单元中K点处的价带最大值（VBM）分裂（Delta）作为压力的函数，实验探测了MoS2和其他TMD中的vdW相互作用。随着高压增加层间波函数耦合，VBM分裂在2H堆叠的MoS2多层膜中增强，但由于其特定的几何形状，而不是在3R堆叠的多层膜中，因此允许将层间贡献从总VBM分裂中分离出来，以及预测层间贡献消失的负压（2.4 GPa）。该负压表示阈值vdW相互作用，超过该阈值vdW相互作用，相邻层被电子解耦。这种方法相比，第一性原理计算，并发现是广泛适用于其他第六组TMD。
van der Waals (vdW) forces, despite being relatively weak, hold the layers together in transition metal dichalcogenides (TMDs) and play a key role in their band structure evolution, hence profoundly affecting their physical properties. In this work, we experimentally probe the vdW interactions in MoS2 and other TMDs by measuring the valence band maximum (VBM) splitting (Delta) at K point as a function of pressure in a diamond anvil cell. As high pressure increases interlayer wave function coupling, the VBM splitting is enhanced in 2H-stacked MoS2 multilayers but, due to its specific geometry, not in 3R-stacked multilayers, hence allowing the interlayer contribution to be separated out of the total VBM splitting, as well as predicting a negative pressure (2.4 GPa) where the interlayer contribution vanishes. This negative pressure represents the threshold vdW interaction beyond which neighboring layers are electronically decoupled. This approach is compared to first-principles calculations and found to be widely applicable to other group-VI TMDs.