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 α-graphyne nanoribbons (ZαGNRs). It is found that asymmetric ZαGNRs behave as conductors with linear current-voltage relationships, whereas symmetric ZαGNRs 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 π and π* 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 ZαGNRs. 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 5000.16em0ex000% is also predicted. Our calculations suggest ZαGNRs as a promising candidate material for spintronics.