Molecular spin qubits are attractive targets for next-generation quantum technologies [1] due to their intrinsic tunability via coordination chemistry techniques, enabling precise control of the relevant spin degrees of freedom and the possibility for massive scale-up via self-assembly. Here, we demonstrate chemical control of the degree of s-orbital mixing into the spin-bearing d-orbital associated with a series of spin-½ La(II) and Lu(II) molecules. Increased s-orbital character reduces spin-orbit coupling and enhances the electron-nuclear Fermi contact interaction. Both outcomes are beneficial for quantum applications: the former reduces spin-lattice relaxation, while the latter gives rise to a record molecular hyperfine interaction for Lu(II) that, in turn, generates a massive 9.2 GHz hyperfine clock transition and an order of magnitude increase in phase memory time. These findings suggest new strategies for development of molecular quantum technologies, similar to trapped ion systems.

Record 9.2 GHz clock transition in a Lu(II) molecular spin qubit arising from a massive 3467 MHz hyperfine interaction

ACS Spring 2022

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