They found that in 1T-TiTe2/ 1T-TiSe2 heterostructures, when the twist angle is near ~ 0.5 °, the extensive 2 × 2 CDW domains are formed in 1T-TiTe2. The CDW domains are caught in the moiré pattern and separated by the 1 × 1 normal-state areas.
Figure 3. Symmetric pressure map. Credit: Image by NJU
This CDW state is substantially enhanced to persist even at space temperature level. In larger twist angles, such moiré-trapped CDW patterns have actually not been observed. Using first-principles computations within the structure density practical theory, they showed that the formation of moiré-trapped CDW state can be ascribed to the local strain variations due to atomic reconstructions regulated by moiré patterns.
Figure 4. Relative height and strain field of the heterostructures. Credit: Image by IoP
This study paves a brand-new way to constructing metal twisted vdW bilayers and tuning the many-body impacts through moiré engineering and it was supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences.
Referral: “Moiré enhanced charge density wave state in twisted 1T-TiTe2/ 1T-TiSe2 heterostructures” by Wei-Min Zhao, Li Zhu, Zhengwei Nie, Qi-Yuan Li, Qi-Wei Wang, Li-Guo Dou, Ju-Gang Hu, Lede Xian, Sheng Meng and Shao-Chun Li, 16 December 2021, Nature Materials.DOI: 10.1038/ s41563-021-01167-0.
Figure 1. Scanning tunneling microscopy topographic images of different moiré patterns with various twist angles. Credit: Image by NJU
When stacking 2 layers of van der Waals (vdW) products, a moiré pattern is produced by the modulation of the long wavelength routine capacity. The moiré pattern is an appealing means in engineering both the atomic geometry and electronic structure. A variety of emergent phenomena have been found in twisted vdW bilayers of graphene or semiconducting transition-metal dichalcogenide (2H-TMD), however, little is learnt about the twisted bilayer of metallic 1T-TMD (transition metal dichalcogenide) products.
In a research study published in Nature Materials, scientists led by Prof. LI Shaochun at Nanjing University and Prof. MENG Sheng at the Institute of Physics (IoP) of the Chinese Academy of Sciences have found for the very first time that the many-body results, especially the electronic quantum correlation, can be tuned in metallic vdW monolayers through moiré engineering.
Figure 2. Moiré enhanced CDWs near 0 °. Credit: Image by NJU and IoP
The scientists manufactured the epitaxial heterostructure of 1T-TiTe2/ 1T-TiSe2 with various twist angles utilizing molecular beam epitaxy and investigated the moiré pattern induced/enhanced charge density wave (CDW) states with scanning tunneling microscopy.
Scanning tunneling microscopy topographic images of different moiré patterns with various twist angles. When stacking two layers of van der Waals (vdW) products, a moiré pattern is produced by the modulation of the long wavelength routine potential. The moiré pattern is a promising methods in engineering both the atomic geometry and electronic structure. Using first-principles calculations within the framework density functional theory, they showed that the development of moiré-trapped CDW state can be ascribed to the local pressure variations due to atomic reconstructions modulated by moiré patterns.
