▎ 摘　　要

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 T-K'K'), and the valley polarization efficiency P-KK' correspond to the subband edges of the right/left ZGNR that are controlled by N-R/N-L. The intervalley transmission coefficients (T-KK' and T-K'K) exhibit peaks at most of the subband edge of the left and right ZGNRs. In the bulk gap of the right ZGNR, T-KK' =T-K'K=0, and P-KK' = +/- 1, the valley polarization is well preserved. As N-R increases, the energy region for P-KK' = +/- 1 decreases. When N-L is fixed and N-R decreases, G, T-KK, T-K'K' and P-KK' exhibit more and more dips, and the peaks of T-KK cent'(T-K'K) 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.