Electrically Tuned Hyperfine Coupling in Neutral Tb(II)-based Single-Molecule Magnet

Electronic and nuclear spin levels of molecules and defects in solids have been shown to be good candidates for qubits. In order to control the level separations and qubit operations, an electric field or voltage was used for deep dopants in semiconductors. This is possible due to a strong interaction between the nuclear spin of the dopant and the electron spin density at the nucleus. Inspired by the solid-state systems, we propose that divalent lanthanide (Ln) complexes with unusual electronic configurations have a strong interaction between the Ln nuclear spin and the electronic degrees of freedom, which renders electrical tuning of the interaction. As a prototype example, we study hyperfine interaction of the Tb nucleus for a neutral Tb(II)(Cp^iPr5)₂ molecule with long magnetization relaxation time, using the multiconfigurational quantum chemistry methods including spin-orbit coupling. We find that the hyperfine interaction is one order of magnitude greater than that for Tb(III)Pc₂. We also uncover that the response of the Fermi contact term to an electric field results in electrical tuning of the nuclear level separations.