Modulate the direct-current and alternating-current transport properties of magnetic γ-graphyne heterojunctions by chemical modification

Using density functional theory and the non-equilibrium Green's function method, we theoretically investigated the direct-current (DC) and alternating-current (AC) quantum transport properties of magnetic γ-graphyne heterojunctions. For the DC case, we found that the γ-graphyne heterojunction has rich transport properties such as spin-filtering and magnetoresistance effects. As the marginal H atoms of the heterojunction are replaced by O atoms, an outstanding dual spin-filtering phenomenon appears and the magnetoresistance is enhanced. Meanwhile, after chemical modification, the heterojunction exhibits a noticeable rectification effect. For the AC case, depending on the frequency, the total and spin AC conductances can be capacitive, inductive, or resistive. At some given frequencies, the signs of the imaginary parts of the AC conductances for two different spins are opposite; thus, the two spin currents have opposite AC responses. A significant photon-assisted tunneling effect was found in the heterojunctions at high frequency range. More interestingly, after chemical modification in a wide frequency range, the imaginary part of the AC conductance changes the sign, indicating that the AC transport properties of the γ-graphyne heterojunction can be effectively modulated by chemical methods.