研究目的
Investigating the impacts of in-plane strain on two different class of commensurate twisted bilayer graphene (TBG) which are even/odd under sublattice exchange (SE) parity.
研究成果
The study concludes that biaxial tensile strains leave the low-energy behavior of the SE odd TBG unchanged whilst they lead to an increment of bandgap for the SE even superlattice. For mixed and uniaxial strains, both superlattices show similar changes in the electronic bandgap. Large mixed strains lead to direct-indirect bandgap crossover. The renormalized Fermi velocity for both SE odd and even superstructures scales inversely with the applied biaxial strain.
研究不足
The study is limited to theoretical calculations and does not include experimental validation. The computational models may not fully capture all physical phenomena due to simplifications.
1：Experimental Design and Method Selection:
Density functional theory (DFT) and tight-binding (TB) calculations were employed to study the impacts of in-plane strain on commensurate twisted bilayer graphene (TBG) superlattices.
2：Sample Selection and Data Sources:
Two commensurate supercells, (m, n) = (1, 4) and (1,3), that are even and odd under SE parity respectively, were selected.
3：List of Experimental Equipment and Materials:
Computational methods were used, specifically the SIESTA code for DFT calculations with double-ζ polarized basis (DZP) and Norm-conserving pseudopotential.
4：Experimental Procedures and Operational Workflow:
The band dispersion for unstrained TBG structures was obtained by relaxing both atomic coordinates and lattice vectors. For strained structures, supercell vectors were modified and the TBG structure was optimized within DFT method.
5：Data Analysis Methods:
The eigen energies and band dispersion of TBGs were calculated through a Hamiltonian approach, and the modification of the band spacing and Fermi velocity was computed.
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