Enhanced\nControl of Single-Molecule Emission Frequency\nand Spectral Diffusion

The Stark effect\nprovides a powerful method to shift the spectra\nof molecules, atoms, and electronic transitions in general, becoming\none of the simplest and most straightforward ways to tune the frequency\nof quantum emitters by means of a static electric field. At the same\ntime, in order to reduce the emitter sensitivity to charge noise,\ninversion symmetric systems are typically designed, providing a stable\nemission frequency with a quadratic-only dependence on the applied\nfield. However, such nonlinear behavior might be reflected in correlations\nbetween the tuning ability and unwanted spectral fluctuations. Here,\nwe provide experimental evidence of this trend using molecular quantum\nemitters in the solid state cooled down to liquid helium temperatures.\nWe finally combine the electric field generated by electrodes, which\nis parallel to the molecule’s induced dipole, with optically\nexcite long-lived charge states acting in the perpendicular direction.\nBased on the anisotropy of the molecule’s polarizability, our\ntwo-dimensional control of the local electric field allows us not\nonly to tune the emitter’s frequency but also to sensibly suppress\nthe spectral instabilities associated with field fluctuations.