Interesting quantum phenomena can be revealed when low dimensional materials are subject to external fields. In our work we theoretically investigate how external fields influence the transport properties of graphene nanoribbons. We demonstrate that armchair-edge nanoribbons subject to a time-periodic gate potential show the so called quantum wagon-wheel effect, in which Fabry-Perot oscillations can be periodically suppressed or recovered as a function of the AC parameters[1]. For zigzag-edge nanoribbons, more intriguing phenomena take place due to the existence of edge states. Essentially, Fabry-Perot oscillations manifest in a limited range of bias and gate voltages and they cannot be totally recovered by tuning the AC gate. Furthermore, zigzag nanoribbons having a Klein edge are expected to yield spinpolarized bands when described by mean-field Hubbard Hamiltonian. Here we also show that the presence of a DC external gate in zigzagedge systems suppresses the characteristic edge states. This leads to atransition from a completely spin-polarized semiconducting system toone which is non-magnetic and metallic.
[1] L. E. F. Foa Torres, G. Cuniberti, cond-mat arXiv. 0807.4953