Spin-dependent transport through interacting graphene armchair nanoribbons

We investigate spin effects in transport across fully interacting, finite size graphene armchair nanoribbons (ACNs) contacted to collinearly spin-polarized leads. In such systems, the presence of short ranged Coulomb interaction between bulk states and states localized at the ribbon ends leads to novel spin-dependent phenomena. Specifically, the total spin of the low energy many-body states is conserved during tunneling but that of the bulk and end states is not. As a consequence, in the singleelectron regime, dominated by Coulomb blockade phenomena, we find pronounced negative differential conductance features for ACNs contacted to parallel polarized leads. These features are however absent for an anti-parallel contact configuration, which in turn leads within a certain gate and bias voltage region to a negative tunneling magneto-resistance. Moreover, we analyze the changes in the transport characteristics under the influence of an external magnetic field. PACS numbers: 72.25.-b Spin-polarized transport; 72.80.Vp Electronic transport in graphene; 73.23.Hk Coulomb blockade; singleelectron tunneling; Spin-dependent transport through interacting graphene armchair nanoribbons 2 Figure 1. A graphene armchair nanostripe contacted by ferromagnetic leads. At the long sides, the lattice is terminated in armchair, at the small ends in zig-zag configuration. The length of a bond between two carbon atoms is a0 ≈ 0.14 nm. We choose the orientation of the coordinate system such that the x-axis points along the zigzag ends, the y-axis along the long armchair edges of the stripe.