Optically and electrically controllable adatom spin-orbital dynamics in transition metal dichalcogenides

We analyze the interplay of spin-valley coupling, orbital physics and magnetic anisotropy taking place at single magnetic atoms adsorbed on semiconducting transition-metal dichalcogenides, MX\(_2\) (M = Mo, W; X = S, Se). Orbital selection rules turn out to govern the kinetic exchange coupling between the adatom and charge carriers in the MX\(_2\) and lead to highly orbitally dependent spin-flip scattering rates, as we illustrate for the example of transition metal adatoms with \(d^9\) configuration. Our ab initio calculations suggest that \(d^9\) configurations are realizable by single Co, Rh, or Ir adatoms on MoS\(_2\), which additionally exhibit a sizable magnetic anisotropy. We find that the interaction of the adatom with carriers in the MX\(_2\) allows to tune its behavior from a quantum regime with full Kondo screening to a regime of "Ising spintronics" where its spin-orbital moment acts as classical bit, which can be erased and written electronically and optically.