▎ 摘　　要

Spin-dependent electronic transport properties in zigzag graphene nanoribbons (ZGNRs) are studied using first-principles quantum transport calculations. The effects of the symmetry and defect have been considered. The results show that when the spin polarization is considered, both symmetric and asymmetric ZGNRs present semiconductor behavior, which is different from spin-unpolarized result. The symmetry of ZGNRs plays an important role in electron transport behavior. Asymmetric ZGNR displays monotonic transport behavior. However, in symmetric ZGNRs systems, negative differential resistance is observed. The influence of defect is more obvious in symmetric ZGNRs than in asymmetric systems. A physical analysis of these results is given.