Electronic structure of quantum defects

Point defects in wide-bandgap materials host localized electronic states that can function as atomic-scale quantum sensors, single-photon emitters, and qubits. The nitrogen-vacancy (NV) center in diamond is a prototypical example: its spin state can be initialized, manipulated, and read out optically at room temperature, making it a versatile platform for quantum sensing and quantum information. Our group studies the electronic structure of such defects from first principles, with the goal of understanding and controlling their optical, spin, and charge properties.

A central theme of our work is how the local environment of a defect shapes its behavior. Using quantum embedding methods and density-functional theory, we have studied how strain fields and external electric fields shift the optical transition energies of the NV⁻ center through the Stark effect, providing quantitative predictions relevant to diamond-based sensors. We have also investigated photoinduced charge dynamics at shallow defects and the role of the surrounding crystal in mediating charge transport between individual color centers.

Beyond the NV center, we study other color centers in diamond and related materials such as hexagonal boron nitride (hBN). Group-III and group-IV substitutional defects in diamond exhibit strong spin-orbit coupling, which quenches the spin and affects coherence properties in ways that are only accessible through careful ab initio treatment. More broadly, understanding the interplay between defect electronic structure, phonon coupling, and photonic environment — for instance, how topological photonic modes can reshape the emission spectrum of an NV center — is an active direction in the group (López-Morales et al., 2024; Kumar et al., 2025).