Negative Differential Resistance of Au-MgB₂-Au Nanoscale Junctions

The electron transport of linear atomic chain of MgB₂ sandwiched between Au(100) elec-trodes was investigated by using the density functional theory with the non-equilibrium Green's function method. We have calculated the corresponding cohesion energy and con-ductance of junctions in different distance. It is found that, at the equilibrium position, the Au?B bond-length is 1.90 ?, the B-Mg bond-length is 2.22 ?, and the equilibrium conduc-tance is 0.51G₀ (G₀=2e²/h). The transport channel is almost formed by the π antibonding orbitals, which was made up of the p_x and p_y orbital electrons of B and Mg atoms. In the voltage range of -1.5 to 1.5 V, the junctions show the metallic behaviors. When the voltage is larger than 1.5 V, the current decreases gradually and then negative differential resistance appears almost symmetrically on both positive and negative bias.