Electronic structure of the neutral silicon-vacancy center in diamond

Abstract

The neutrally-charged silicon vacancy in diamond is a promising system for quantum technologies that combines high-efficiency, broadband optical spin polarization with long spin lifetimes (T2 ≈ 1 ms at 4 K) and up to 90 % of optical emission into its 946 nm zero-phonon line. However, the electronic structure of SiV 0 is poorly understood, making further exploitation difficult. Performing photoluminescence spectroscopy of SiV 0 under uniaxial stress, we find the previous excited electronic structure of a single 3 A1u state is incorrect, and identify instead a coupled 3 Eu − 3 A2u system, the lower state of which has forbidden optical emission at zero stress and so efficiently decreases the total emission of the defect: we propose a solution employing finite strain to form the basis of a spin-photon interface. Isotopic enrichment definitively assigns the 976 nm transition associated with the defect to a local mode of the silicon atom.

The (eg ⊗ eu) ⊗ Eg product Jahn–Teller effect in the neutral group-IV vacancy quantum bits in diamond

“…(iii) The 946-nm ZPL intensity will be temperature dependent, as it depends on the thermal occupation of the 3 E u over the lowest energy A 2u . These properties were indeed observed in previous experiments [34,36].…”

“…Experimental data are only available for SiV(0), thus we can directly compare our results only to them. A recent stress measurement on the photoluminescence (PL) spectrum of SiV(0) revealed a dark state where the corresponding level was below the ZPL energy by 6.8 meV [36]. Our calculations explain this feature by the pJT effect of the three triplet excited states.…”

“…(1). Additionally, the (e g e u ) excited singlet levels are expected to lie above the (e g e u ) excited triplets due to the Coulomb repulsion [31,36]. We show the single determinant states of the triplets in Eq.…”

“…In particular, the 946-nm zero-phonon-line (ZPL) optical transition of * gali.adam@wigner.mta.hu SiV(0) (see Refs. 30,[32][33][34][35][36] was originally assigned to an 3 A 2g ↔ 3 A 1u electronic excitation from the ground state to the excited state [5,34], however it has been very recently revealed that the excited state should be a 3 E u state deduced from stress measurements [36]. Furthermore, a dark 3 A 2u state below the 3 E u by 6.7 meV was activated in the luminescence spectrum by exerting uniaxial stress on the diamond sample [36].…”

Quantum nanophotonics with group IV defects in diamond

“…The main drawbacks of the SiV 0 are the relatively low fluorescence at low temperature and unknown precise concentration of boron and nitrogen in the host diamond required to engineer this colour centre efficiently. 80 So far, it was only identified in specifically grown diamonds, provided by Element Six. 78,80…”