Magnetic impurity affected by spin-orbit coupling: Behavior near a topological phase transition

Abstract

We investigate the effect of spin-orbit coupling on the behavior of a magnetic impurity at the edge of a zigzag graphene ribbon by means of quantum Monte Carlo simulations. A peculiar interplay of Kane-Mele type spin-orbit and impurity-host coupling is found to greatly affect properties for the local moment. The local characters of the impurity are mainly dominated by the local density of states at the edge, such as double occupancy, magnetic moment, and spin susceptibilities. The special helical nature of the topological insulator on the boundary is found to affect nonlocal quantities, such as the two-particle and spin-spin correlation functions linking electrons on the impurity with those in the conduction band; in particular, due to the spin-orbit coupling, the symmetry of the spin rotation in the Kondo cloud around the impurity is partly broken.