Abstract
In this work, we investigate the role of an external electric field in modulating the spectrum and electronic structure behavior of twisted bilayer graphene (TBG) and its physical mechanisms. Through theoretical studies, it is found that the external electric field can drive the relative positions of the conduction band and valence band to some extent. The difference of electric field strength and direction can reduce the original conduction band, and through the Fermi energy level, the band is significantly influenced by the tunable electric field and also increases the density of states of the valence band passing through the Fermi level. Under these two effects, the valence and conduction bands can alternately fold, causing drastic changes in spectrum behavior. In turn, the plasmon spectrum of TBG varies from semiconductor to metal. The dielectric function of TBG can exhibit plasmon resonance in a certain range of infrared.
Highlights
The “magic angle” graphene is similar to the structure of a heterostructure
We have theoretically investigated the optical properties of twisted bilayer graphene (TBG) under the modulation of an external electric field, with the lower layer rotated by 21.67◦ with respect to the upper layer (Figure 1a)
The force constants obtained by the density general function theory solution combined with the constants obtained by theand density general function solution the pseudo-Newton method the conjugate gradienttheory descent methodcombined to obtain with the minpseudo-Newton method and the conjugate gradient descent method to obtain the minimum imum interaction distance between layers are the distance between layers
Summary
Bilayer heterostructures have received much attention in recent years, and transition metal element heterostructures exhibit fascinating physical properties [1,2]. Twisted bilayer graphene (TBG) has received much attention. The relative rotation angle between the double-layer graphene layers forms a twisted bilayer graphene. Cao et al first reported the coupling and strong interaction between electrons in magic-angle graphene, which led to the observation of the quantum correlation in the entire corner double-layer graphene system [3,4,5]. In the corner double-layer graphene, from the perspective of the lattice structure, the original symmetrical rhombohedral unit cell has become a larger scale extended unit cell, and the entire system exhibits a periodic variation of Moiré superlattice (MS). The appearance of the torsion angle in the two-layer graphene determines that the
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