Journal
COMPUTATIONAL MATERIALS SCIENCE
Volume 199, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.commatsci.2021.110746
Keywords
Twisted bilayer graphene; In-plane relaxation; Diffraction pattern; Moire; Electron localization
Categories
Funding
- Army Research Office Material Science Division [W911NF-17-1-0544]
- National Science Foundation [1555278]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Computational Materials Sciences program [DE-SC0020177]
- U.S. Department of Energy (DOE) [DE-SC0020177] Funding Source: U.S. Department of Energy (DOE)
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1555278] Funding Source: National Science Foundation
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In low-angle twisted bilayer graphene, electronic properties are influenced by the atomic structure; relaxation causes changes in symmetry; a computationally efficient framework has been developed to explore charge density symmetry.
Electronic properties such as band structure and Fermi velocity in low-angle twisted bilayer graphene (TBG) are intrinsically dependent on the atomic structure. Rigid rotation between individual graphene layers provides an approximate description of the bilayer symmetry. Upon relaxation, in-plane displacement of the atoms in low angle TBG causes a change in the symmetry through the enlargement of the AB stacking regions and the reduction in size of AA and SP stacking regions. However, the effect of this in-plane relaxation on the charge density remains unexplored, because the necessary electronic structure calculations of such large supercells of low twist angle TBG are computationally infeasible. Therefore, we develop a computationally efficient framework that enables the exploration of the charge density symmetry of the low twist angle TBG. This framework is based on the Fourier representation of the charge density which presents high intensity Bragg peaks. We find that with the decrease of twist angle, low intensity satellite peaks also become apparent. Our framework incorporates these satellite peaks which reveals transformation of symmetry in the charge density distribution from high to low twist angle TBG. One striking outcome is the demonstration of the electron localization in the AA region of low twist angle TBG. Our framework helps to explain the effect of the atomistic relaxation on the charge density distribution and thus, it provides information about exotic electronic properties of low twist angle TBG at a low computational expense.
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