Chiral magnetic interactions in graphene nanoribbons on topological insulator substrates

It is known that the interplay between strong spin-orbit coupling and broken inversion symmetry can lead to chiral configurations in low-dimensional magnetic systems deposited on heavy-element surfaces. This phenomenon is due to the Dzyaloshinskii-Moriya interaction, which favours noncollinear magnetic structures. Here we show by ab initio simulations that this interaction leads to a twisting of the two antiferromagnetically coupled edge-state spins of a zigzag graphene nanoribbon deposited on the topological insulator Sb2Te3. To our knowledge, this is the first report of a chiral magnetic structure formed by a pair of one-dimensional states. This effect results in a finite net magnetization in the nanoribbons, which could lead to applications such as spin filters in graphene-based spintronics devices.