▎ 摘　　要

The zigzag graphene nano-ribbon (ZGNR) has a novel physical property called the quantum spin Hall effect (QSHE). In this paper, we use the Landauer method to calculate the current and polarization on two types of branching ZGNR (fork-shaped and H-shaped). Our results indicate that the branch-shape graphene device will enhance the spin polarizing current. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3684714]