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Layer-Dependent Electromechanical Response in Twisted Graphene Moiré Superlattices
Hanhao Zhang1, Yuanhao Wei2, Yuhao Li1,3
1National Laboratory of Solid-State Microstructures, School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, Jiangsu, China.
ACS Nano
|June 27, 2024
Summary
Researchers explored electromechanical responses in twisted graphene moiré superlattices. Twisted monolayer-bilayer graphene (tMBG) shows a stronger piezoelectric effect than twisted bilayer graphene (tBLG), suggesting different nanoscale coupling mechanisms.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Twisted van der Waals (vdW) materials, particularly twisted graphene, are platforms for exotic quantum states.
- Moiré superlattices in these materials enable visualization via electromechanical response.
- The origin of electromechanical responses in twisted bilayer graphene (tBLG) is not fully understood.
Purpose of the Study:
- To investigate the electromechanical responses of twisted graphene moiré superlattices with varying layer thicknesses.
- To differentiate the electromechanical coupling mechanisms in twisted bilayer graphene (tBLG) and twisted monolayer-bilayer graphene (tMBG).
- To provide insights into nanoscale electromechanical and cooperative effects in vdW materials.
Main Methods:
- Utilized lateral piezoresponse force microscopy (LPFM) to probe electromechanical responses.
- Examined marginally twisted graphene moiré superlattices of different layer thicknesses.
- Conducted force tuning experiments to analyze response behaviors.
Main Results:
- Observed distinct LPFM amplitudes and spatial profiles in tBLG and tMBG.
- Quantified effective in-plane piezoelectric coefficients: 0.05 pm/V for tBLG and 0.35 pm/V for tMBG.
- Demonstrated divergent responses between tBLG and tMBG, suggesting different coupling mechanisms.
Conclusions:
- The electromechanical response in tBLG is primarily attributed to the flexoelectric effect near domain walls.
- The response in tMBG is consistent with the piezoelectric effect.
- Results offer insights into electromechanical coupling in twisted vdW materials with varying stacking symmetries and potential for nanoscale engineering.
