Reversed even-odd oscillation of spin-polarized equilibrium conductance in an all-carbon junction

Abstract

Recently, considerable attention has been paid to exploring the full potential of molecular spintronics; application based on all-carbon devices has drawn much attention. Whether the equilibrium conductance of linear carbon atomic chains (CAC) has an even-odd oscillation (EOO) or reversed EOO (REOO) behavior is critically important but still an open problem. Its answer will in large part determine various transport properties of the junction. Here, we systematically study the spin-dependent electron transport through CAC bridging of two perfect zigzag graphene nanoribbons (ZGNRs) using a nonequilibrium Green’s function approach combined with density functional theory calculations. As well as EOO and disappearing EOO, the equilibrium conductance shows an unexpected REOO in the all-carbon junctions, depending strongly on the position and tilting angle of the CAC bridging the gap. The REOO is due to a resonant state that occurs between even-numbered CAC and the ZGNR lead, whereas odd-numbered CAC case has no such resonant state. It indicates that the physical origin of REOO is different from that of EOO. Moreover, the REOO behavior is robust against variations in lead width and CAC length. Our findings may help in designing CAC spintronic on-chip all-carbon devices with various functionalities.