Photo-induced lattice contraction in layered materials
Photo-induced lattice contraction in layered materials
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DOI：
10.1088/1361-648x/aad022
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发表时间：
2018-07
期刊：
影响因子：
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通讯作者：
H. Kumazoe;A. Krishnamoorthy;Lindsay Bassman;R. Kalia;A. Nakano;F. Shimojo;P. Vashishta
中科院分区：
文献类型：
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作者：
H. Kumazoe;A. Krishnamoorthy;Lindsay Bassman;R. Kalia;A. Nakano;F. Shimojo;P. Vashishta
光激发引起的结构和电子变化是一种很有前途的二维晶体功能化技术。表征激发态对面内共价键网络的影响以及相对较弱的面外色散相互作用对于调整这些高度各向异性晶体结构中的光响应是必要的。利用泵浦-探测实验测量了面内原子动力学，并用从头计算方法对其进行了表征，但电子激发对弱面外van der Waals键的影响研究较少。我们用非绝热量子分子动力学研究了光激发MoS_2双层膜中的原子运动。我们观察到，在电子激发后的100fs内，晶格参数沿面外方向发生了强烈的非热还原，这是由于电子重新分布到层间具有较小反键性质的激发态所致。这种在光激发过程中弱键相互作用的非平凡行为可能在包含非共价相互作用的材料体系中具有潜在的应用，如层状材料和聚合物。
Structural and electronic changes induced by optical excitation is a promising technique for functionalization of 2D crystals. Characterizing the effect of excited electronic states on the in-plane covalent bonding network as well as the relatively weaker out-of-plane dispersion interactions is necessary to tune photo-response in these highly anisotropic crystal structures. In-plane atom dynamics was measured using pump-probe experiments and characterized using ab initio simulations, but the effect of electronic excitation on weak out-of-plane van der Waals bonds is less well-studied. We use non-adiabatic quantum molecular dynamics to investigate atomic motion in photoexcited MoS2 bilayers. We observe a strong athermal reduction in the lattice parameter along the out-of-plane direction within 100 fs after electronic excitation, resulting from redistribution of electrons to excited states that have lesser anti-bonding character between layers. This non-trivial behavior of weakly bonded interactions during photoexcitation could have potential applications for modulating properties in materials systems containing non-covalent interactions like layered materials and polymers.