Influence of Coupling Strength Between a Magnetic Quantum Dot and Quantum Hall Edge Channels on Valley-isospin-dependent Dirac Fermion Transport

Abstract

We investigate Dirac fermion transport through opposite quantum Hall edge channels in armchair graphene nanoribbons where a magnetic quantum dot (MQD) is placed between the edges. The resulting conductance shows distinguished resonant features according to the angle Φ between the valley isospins at the opposite edges. Particularly, for Φ = 0, the conductance exhibits a behavior characteristic of dissipative resonances when the edge—dot distance is sufficiently small even though the unitarity of the whole system is conserved. As the edge—dot distance increases, a crossover behavior emerges between two distinct regimes: largely perturbed and unperturbed MQD. Resonant energy converges to a specific energy corresponding to the eigenenergy of the localized states in the unperturbed MQD. For sufficiently weak couplings, a fine splitting of the conductance resonances is observed, of which splitting energy is several μeV. The finding of these finely split localized states in the MQD allows us to better elucidate related electronic and transport properties in graphene.