LONG RANGE DYNAMICAL COUPLING BETWEEN MAGNETIC ADATOMS MEDIATED BY EDGE STATES IN A 2D TOPOLOGICAL INSULATOR*

We study the spin excitation spectra and the dynamical exchange coupling between iron adatoms on a bismuthene nanoribbon. We show that the topological character of the edge states is preserved in the presence of the magnetic adatoms. Nevertheless, they couple significantly to the edge spin currents, as witnessed by the large and long-range dynamical coupling we obtain in our calculations. The large effective magnetocrystalline anisotropy of the magnetic adatoms combined with the transport properties of the topologically protected edge states make this system a strong candidate for implementation of spintronics devices. We use a multi-orbital tight-binding Hamiltonian to describe the electronic structure of the decorated nanoribbon. The full Hamiltonian can be written as the sum of band energy H0, effective intra-atomic Coulomb repulsion HI and the atomic spin-orbit coupling HSOC. The hopping matrix is obtained directly from a DFT calculation using the pseudo-atomic orbital projection method[1].

[1] M. B. Nardelli, F. T. Cerasoli, M. Costa, S. Curtarolo, R. D. Gennaro, M. Fornari, L. Liyanage, A. R. Supka, and H. Wang, Computational Materials Science 143, 462 (2018).