Electromechanical switching in graphene nanoribbons

We investigate the effect of twisting on the electronic, magnetic and transport properties of zigzag graphene nanoribbon (ZGNR) using density functional theory (DFT) calculations. We compare electronic and magnetic properties of ZGNR in both planar and 180°-twisted geometries. Furthermore, combining DFT with the nonequilibrium Green's function method (NEGF), we examine the quantum conductance of twisted ZGNR in its antiferromagnetic and ferromagnetic states. Consequently, the structure of local magnetic moments in the region between electrodes of opposite magnetization behaves as a Bloch/Neel domain wall. Our calculations show that ZGNR in its ground state (antiferromagnetic) is insensitive to twisting, there is no band gap change, and the conductance of the twisted ZGNR is almost unchanged as well. We demonstrate that the electromechanical switching can be realized by twisting a ferromagnetic ZGNR, which is an ideal spin valve in case of oppositely polarized leads (after twisting).