Speaker:Dr. Churna Bhandari

Dr. Churna Bhandari

Ames Laboratory

Title: Negatively Charged Nitrogen Vacancy Center in Diamond: A Multiconfigurational Quantum Chemistry Approach

Abstract: In recent years, the negatively charged nitrogen-vacancy (NV-) center in diamond crystal has brought in an explosion of research interest as a promising quantum defect useful for quantum sensing and information applications. The highly localized negatively charged vacancy in a transparent solid-state diamond matrix and the distributions of active electrons around the broken-dangling bonds of carbon and nitrogen atoms nearest to the vacancy result in multiconfigurational electronic spin-triplet and spin-singlet states deep inside the electronic bandgap of the host material. In particular, energies of spin-triplet states are very sensitive to the spin-orbit interaction and the dipolar spin-spin interactions. We study the electronic and magnetic properties of the NV- center by proper treatment of electron correlations, spin-orbit coupling, and dipolar spin-spin interactions within multiconfigurational quantum chemistry methods. Our results show the correct ordering of the triplet and singlet states as well as the excitation energies (separation between ground triplet state 3A2 and excited states) as observed in the experiment. We show the many body configurations nature of the spin-singlet states, which otherwise cannot be described by traditional single-particle density functional methods. Our calculated zero-field splitting and the ordering of the split levels of ground triplet state 3A2 are in excellent agreement with the experiment. Finally, we show the splitting of orbital doublet (the first excited spin-triplet states 3E) into four levels due to a combined effect of spin-orbit and dipolar spin-spin interaction, and our calculated energy values agree with the experiment. The numerical method we have developed in this calculation is general and can also be used to other quantum defects.