Single spin resonance driven by electric modulation of the g factor anisotropy

We address the problem of electronic and nuclear spin resonance of an individual atom on a surface driven by a scanning tunnelling microscope. Several mechanisms have been proposed so far, some of them based on the modulation of exchange and crystal field associated to a piezoelectric displacement of the adatom driven by the RF tip electric field. Here we consider a new mechanism, where the piezoelectric displacement modulates the g factor anisotropy, leading both to electronic and nuclear spin flip transitions. We discuss thoroughly the cases of Ti-H (S = 1/2) and Fe (S = 2) on MgO, relevant for recent experiments. We model the system using two approaches. First, an analytical model that includes crystal field, spin orbit coupling and hyperfine interactions. Second, we carry out density functional based calculations. We find that the modulation of the anisotropy of the g tensor due to the piezoelectric displacement of the atom is an additional mechanism for STM based single spin resonance, that would be effective in S = 1/2 adatoms with large spin orbit coupling. In the case of Ti-H on MgO, we predict a modulation spin resonance frequency driven by the DC electric field of the tip.