The neutral silicon-vacancy center in diamond: spin polarization and lifetimes

We demonstrate optical spin polarization of the neutrally-charged silicon-vacancy defect in diamond ($\mathrm{SiV^{0}}$), an $S=1$ defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but non-zero at below-resonant energies. We measure an ensemble spin coherence time $T_2>100~\mathrm{\mu s}$ at low-temperature, and a spin relaxation limit of $T_1>25~\mathrm{s}$. Optical spin state initialization around 946 nm allows independent initialization of $\mathrm{SiV^{0}}$ and $\mathrm{NV^{-}}$ within the same optically-addressed volume, and $\mathrm{SiV^{0}}$ emits within the telecoms downconversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that $\mathrm{SiV^{0}}$ is a promising candidate for a long-range quantum communication technology

Electronic structure of the neutral silicon-vacancy center in diamond

The neutrally charged silicon vacancy in diamond is a promising system for quantum technologies that combines high-efficiency optical spin initialization with long spin lifetimes (T2≈1ms 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 SiV0 under uniaxial stress, we find the previous excited electronic structure of a single 3A1u state is incorrect, and identify instead a coupled 3Eu−3A2u system, the lower state of which has forbidden optical emission at zero stress and efficiently decreases the total emission of the defect. We propose a solution employing finite strain to define a spin-photon interface scheme using SiV 0.This work is supported by EPSRC Grants No.EP/L015315/1 and No. EP/M013243/1, and ARC Grants No. DE170100169 and No. DP140103862

Electronic structure of the neutral silicon-vacancy center in diamond

The neutrally-charged silicon vacancy in diamond is a promising system for quantum technologies that combines high-efficiency optical spin initialization 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 SiV0 is poorly understood, making further exploitation difficult. Performing photoluminescence spectroscopy of SiV0 under uniaxial stress, we find the previous excited electronic structure of a single 3A1u state is incorrect, and identify instead a coupled 3Eu − 3A2u system, the lower state of which has forbidden optical emission at zero stress and efficiently decreases the total emission of the defect. We propose a solution employing finite strain to define a spin-photon interface scheme using SiV0

Neutral Silicon-Vacancy Center in Diamond: Spin Polarization and Lifetimes

We demonstrate optical spin polarization of the neutrally charged silicon-vacancy defect in diamond (SiV0), an S ¼ 1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but nonzero at below-resonant energies. We measure an ensemble spin coherence time T2 > 100 μs at low-temperature, and a spin relaxation limit of T1 > 25 s. Optical spin-state initialization around 946 nm allows independent initialization of SiV0 and NV− within the same optically addressed volume, and SiV0 emits within the telecoms down-conversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV0 is a promising candidate for a long-range quantum communication technology

Doubly charged silicon vacancy center, Si-N complexes, and photochromism in N and Si codoped diamond

Diamond samples containing silicon and nitrogen are shown to be heavily photochromic, with the dominant visible changes due to simultaneous change in total SiV0/− concentration. The photochromism treatment is not capable of creating or destroying SiV defects, and thus we infer the presence of the optically inactive SiV2− . We measure spectroscopic signatures we attribute to substitutional silicon in diamond, and identify a silicon-vacancy complex decorated with a nearest-neighbor nitrogen SiVN, supported by theoretical calculations

EPR of a defect in CVD diamond involving both silicon and hydrogen that shows preferential alignment

A defect involving both silicon and hydrogen has been characterized using multifrequency electron paramagnetic resonance. The defect, denoted WAR3, was observed in a single-crystal chemical-vapor deposition diamond, which was homoepitaxially grown on a {110}-oriented substrate and doped with isotopically enriched silicon (90% Si-29). The obtained data are explained by a silicon divacancy structure which is decorated by a hydrogen atom and is in the neutral charge state, (Si-V2:H)(0) (S=1/2). The experimentally derived Si-29 and H-1 hyperfine parameters are in agreement with values calculated using the spin-density-functional technique, ruling out a nonplanar structure. Defects are usually randomly oriented such that there is an equal probability for the symmetry axis of the defect to lie along each of the crystallographically equivalent directions. However, the WAR3 defect shows preferential alignment with respect to the {110} growth plane of the sample. Approximately four times as many WAR3 centers were aligned with their mirror planes lying perpendicular to the growth plane, compared to a statistical distribution. This indicates that the majority of WAR3 defects grew in as units rather than by the diffusion and aggregation of constituents. Analysis of the increase in the WAR3 concentration and the decrease in preferential alignment upon annealing the sample at 1400 degrees C shows that WAR3 can also be created post growth