colored centers in diamond: reexamining the intersystem crossing (ISC) with ΔSCF calculations within density functional theory (DFT) combined to the extended Hubbard model*

The sensitivity of the NV center to its surrounding magnetic field is expected to be a powerful tool to detect the onset of superconductivity at ultrahigh P in diamond anvil cells. In this work, we propose a combined approach to study the many-body excited states of the NV^-center under P: the extended Hubbard model with all of the parameters fit on ΔSCF-DFT calculations of the differences of total energies with constrained occupations, thereby including the electron-hole interaction for any P.
We study the behavior of all of the many body states under P. In particular, we compute for the first time the pressure coefficients of the singlet-singlet emission consecutive to the ISC for the two models reported in the literature [1,2], and show that they are widely different, the application of hydrostatic pressure being an effective tool to discriminate between them.
[1] Doherty, Manson, Delaney, Jelezko, Wrachtrup, Hollenberg, Phys. Rep. 528,1 (2013).
[2] Ma, Rohlfing, Gali, Phys. Rev. B 81, 041204 (2010).