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arXiv 2108.01112cond-mat.mtrl-scicond-mat.mes-hall
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应变工程过渡金属二硫化物双层莫尔体系中的原子弛豫与平带

Atomic relaxation and flat bands in strain-engineered transition metal dichalcogenide bilayer moiré systems

Sudipta Kundu, Indrajit Maity, Robin Bajaj, H. R. Krishnamurthy, Manish Jain

AI总结:

本文研究应变TMD同质双层莫尔体系的原子弛豫与电子结构,揭示拉伸孤子、星形缺陷及价导带边缘平带,并验证波函数局域化与实验一致。

摘要:

应变诱导的晶格失配会在过渡金属二硫化物(TMD)同质双层中产生莫尔图案。我们研究了TMD同质双层中此类应变莫尔图案的结构和电子性质。应变TMD中的莫尔图案由若干堆叠畴组成,这些畴被拉伸孤子分隔。这些体系的弛豫使应变在莫尔超晶格中分布不均,最大应变能集中在能量最高的堆叠处。序参量分布表明,在相同位置形成了星形(aster)拓扑缺陷。相比之下,扭转TMD在畴壁处具有剪切孤子,且这些体系中的序参量分布显示出涡旋缺陷的形成。应变莫尔体系还在价带和导带边缘均出现若干分离良好的平带,并且我们观察到带隙显著减小。这些应变莫尔超晶格中的平带为研究三角晶格上的Hubbard模型以及蜂窝晶格上的离子Hubbard模型提供了平台。此外,我们研究了与这些平带对应的波函数局域化。与扭转TMD相比,波函数局域在不同的堆叠处,我们的结果与光谱实验高度一致。

英文摘要:

Strain-induced lattice mismatch leads to moiré patterns in homobilayer transition metal dichalcogenides (TMDs). We investigate the structural and electronic properties of such strained moiré patterns in TMD homobilayers. The moiré patterns in strained TMDs consist of several stacking domains which are separated by tensile solitons. Relaxation of these systems distributes the strain unevenly in the moiré superlattice, with the maximum strain energy concentrating at the highest energy stackings. The order parameter distribution shows the formation of aster topological defects at the same sites. In contrast, twisted TMDs host shear solitons at the domain walls, and the order parameter distribution in these systems shows the formation of vortex defects. The strained moiré systems also show the emergence of several well-separated flat bands at both the valence and conduction band edges, and we observe a significant reduction in the band gap. The flat bands in these strained moiré superlattices provide platforms for studying the Hubbard model on a triangular lattice as well as the ionic Hubbard model on a honeycomb lattice. Furthermore, we study the localization of the wave functions corresponding to these flat bands. The wave functions localize at different stackings compared to twisted TMDs, and our results are in excellent agreement with spectroscopic experiments.

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