Valley-resolved transport in zigzag graphene nanoribbon junctions

Abstract

Applying the transfer matrix and Green’s function methods, we study the valley-resolved transport properties of zigzag graphene nanoribbon (ZGNR) junctions. The width of the left and right ZGNRs are N L and N R , and N L ≥ N R . The step/dip positions of the conductance G, the intravalley transmission coefficients (T KK and ), and the valley polarization efficiency correspond to the subband edges of the right/left ZGNR that are controlled by N R /N L . The intervalley transmission coefficients ( and ) exhibit peaks at most of the subband edge of the left and right ZGNRs. In the bulk gap of the right ZGNR, =0, and = ±1, the valley polarization is well preserved. As N R increases, the energy region for = ±1 decreases. When N L is fixed and N R decreases, G, T KK , and exhibit more and more dips, and the peaks of () become more and more high, especially when (N L − N R )/2 is odd. These characters are quite useful for manipulating the valley dependent transport properties of carriers in ZGNR junctions by modulating N L or N R , and our results are helpful to the design of valleytronics based on ZGNR junctions.