Symmetry-dependent transport properties and bipolar spin filtering in zigzag α-graphyne nanoribbons

First-principles calculations are performed to investigate the transport properties of zigzag alpha-graphyne nanoribbons (ZaGNRs). It is found that asymmetric Z alpha GNRs behave as conductors with linear current-voltage relationships, whereas symmetric Z alpha GNRs have very small currents under finite bias voltages, similar to those of zigzag graphene nanoribbons. The symmetry-dependent transport properties arise from different coupling rules between the pi and pi* subbands around the Fermi level, which are dependent on the wave-function symmetry of the two subbands. Based on the coupling rules, we further demonstrate the bipolar spin-filtering effect in the symmetric Z alpha GNRs. It is shown that nearly 100% spin-polarized current can be produced and modulated by the direction of bias voltage and/or magnetization configuration of the electrodes. Moreover, the magnetoresistance effect with the order larger than 500 000% is also predicted. Our calculations suggest Z alpha GNRs as a promising candidate material for spintronics. DOI:10.1103/PhysRevB.86.235448