Spin confinement in the superlattices of graphene ribbons

Graphene, a single atomic layer of graphite, has recently been isolated from graphite (which was thought to be impossible for a long time). It has unique properties originating from its honeycomb structure,  such as ballistic transport at room temperature, anomalous quantum Hall effect, etc. These properties can offer several potential applications in future. Graphene nanoribbons have the charge carriers which are confined in two dimension and free to move in third direction. They are particularly important due to their well defined geometry and possible ease of manipulation. Graphene nanoribbons can be characterized according to their edge shape, i.e. armchair or zigzag. Both armchair and zigzag graphene nanoribbons display intresting properties. Armchair nanoribbons have band gaps which are inversely proportional to their widths. On the other hand, zigzag shaped graphene nanoribbons have magnetic edge states with antiferromagnetic behavior which makes them very interesting for spintronic applications. Based on first-principles calculations, we showed that periodically repeated heterostructures of zigzag graphene nanoribbons of different widths form multiple quantum well structures. Edge states of specific spin directions can be confined in these wells. The electronic and magnetic state of the ribbon can be modulated in real space. In specific geometries, the absence of reflection symmetry causes the magnetic ground state of whole heterostructure to change from antiferromagnetic to ferrimagnetic. These quantum structures of different geometries provide unique features for spintronic applications.

M. Topsakal,  H. Sevinçli, and S. Ciraci
APPLIED PHYSICS LETTERS 92, 173118 (2008)
Editorially selected  for Virtual Journal of Nanoscale Science and Technology.