Host-matrix control for improving spin coherence in molecular color centers*

Molecular color centers seek to achieve core functionality of solid-state color centers within a chemically synthesizable molecule [1]. Using a molecular architecture for color centers provides several opportunities to favorably tune their properties, for example, by modifying their host environment. Here we demonstrate how host-matrix control can be used to enhance chromium(IV)-based molecular color centers. We show that inserting these molecules into a non-isostructural host matrix significantly enhances their spin coherence compared to using an isostructural host. This behavior arises from a breaking of the qubit’s symmetry due to the host-matrix, which generates a significant transverse zero-field splitting and creates clock transitions which are insensitive to magnetic-field noise. We find close agreement between our experimental results and first-principles cluster-correlation expansion simulations, and further experimentally demonstrate enhanced optical contrast and spin-lattice relaxation times for host-matrix engineered molecular color centers. These results highlight the modularity and tunability of molecular color centers, indicating their promise for applications such as quantum sensing.

[1] Bayliss*, Laorenza* et al. Science 370, 1309 (2020)

[2] Bayliss*, Deb*, Laorenza* et al. Phys. Rev. X 12, 031028 (2022)