ナノフィジックスの正しいねじり方:積層ナノ半導体材料にわずかなねじれを与え、新しい用途利用できる効果を研究。(Nanophysics: the right twist:Stacked layers of ultrathin semiconductor materials feature phenomena that can be exploited for novel applications. )

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2023-03-28 ミュンヘン大学(LMU)

極薄ナノ材料は新しい物性を示す。層状に重ねた半導体材料の物理的効果は、様々な新しい現象を引き起こす。
LMUの物理学者Alexander Högele率いるチームは、微小なひねりを加えた二層の材料で現れる効果を研究した。
研究チームは、van der Waals力によって維持されるヘテロ二層システムを調べ、これらのシステムでは、個々の層の向きに応じてモアレ効果が生じることが分かった。これにより、電子やエキシトンなどに影響を与える物性が制御可能となり、量子技術、光子学、電子工学などの応用分野で活用可能となる。

<関連情報>

メゾスコピックに再構成されたモアレヘテロ構造における励起子 Excitons in mesoscopically reconstructed moiré heterostructures

Shen Zhao,Zhijie Li,Xin Huang,Anna Rupp,Jonas Göser,Ilia A. Vovk,Stanislav Yu. Kruchinin,Kenji Watanabe,Takashi Taniguchi,Ismail Bilgin,Anvar S. Baimuratov & Alexander Högele
Nature Nanotechnology  Published:27 March 2023
DOI:https://doi.org/10.1038/s41565-023-01356-9

figure 1

Abstract

Moiré effects in vertical stacks of two-dimensional crystals give rise to new quantum materials with rich transport and optical phenomena that originate from modulations of atomic registries within moiré supercells. Due to finite elasticity, however, the superlattices can transform from moiré-type to periodically reconstructed patterns. Here we expand the notion of such nanoscale lattice reconstruction to the mesoscopic scale of laterally extended samples and demonstrate rich consequences in optical studies of excitons in MoSe2–WSe2 heterostructures with parallel and antiparallel alignments. Our results provide a unified perspective on moiré excitons in near-commensurate semiconductor heterostructures with small twist angles by identifying domains with exciton properties of distinct effective dimensionality, and establish mesoscopic reconstruction as a compelling feature of real samples and devices with inherent finite size effects and disorder. Generalized to stacks of other two-dimensional materials, this notion of mesoscale domain formation with emergent topological defects and percolation networks will instructively expand the understanding of fundamental electronic, optical and magnetic properties of van der Waals heterostructures.

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