Controlling the Exchange Field of Surface Spin Impurities via DC Voltages

Recent advances in scanning probe microscopy have demonstrated the quantum-coherent manipulation of individual spins on surfaces using oscillating AC voltages. At the same time, the role of the static voltage in such control schemes remains unclear. Here, we show how the static contribution can be utilized to control the resonance of electronic transitions via an effective exchange field model based on a non-equilibrium transport formalism. We demonstrate that the magnitude and direction of the exchange field can be tuned and turned off by changing the applied bias voltage. Furthermore, our model can accurately reproduce the observed resonance frequency shifts at different magnetic field geometries for two different spin $S=1/2$ adsorbates. This work enables fast and precise control of the quantum states of surface spins at the atomic scale which will aid in developing spin-based quantum technologies.