Geometrical structure and the electron transport properties of monolayer and bilayer silicene near the semimetal-insulator transition point in tight-binding model

Abstract

We investigate the electron properties of the monolayer and bilayer silicene which is the honeycomb lattice consist of silicon atoms, including the optical conductivity and charged impurity scattering, due to the quasipatricle Dirac-like behaviors near the K-point of silicene. The spin, valley, sublattice degrees of freedom are taken into consider in the multi-band tight-binding model. In momentum space, the scattering matrix which connects the two bare (without interaction) Green's functions in the quasiparticle momentum transport process, could be momentum-independent for the single impuirity configuration, which is similar to the case with small Coulomb coupling in the low-energy Dirac semimetallic system. While in the zero-frequency limit, or the frequency-independent case in the strong Coulomb coupling regime, the static polarization can be obtained by the random-phase-approximation, and it's important for the determination of the screened Coulomb scattering by the charge impurity. The antiferromagnetic order in the silicene is Hubbard-U-dependent, unlike the square lattice which with the antiferromagnetic ground state, and provides the premise of the phase transition from the nonmagnetic semimetal phase to the insulator one. We found that in the absence of electric field, the critical value of the phase transition from semimetal to insulator is 9 eV for the clear monolayer silicene, and is 12 eV for the 2nd AA-stacked bilayer silicene or the dirty monolayer silicene whcih with impurity strength 4 eV. While the behaviors of 1st AA-stacked bilayer silicene is found similar to the monolayer one. The in-plane optical conductivity also shows the same results.