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We have investigated the optical properties of the (NV)− center in 3C-SiC to determine the photoluminscence zero phonon line (ZPL) associated with the 3E→3A2 intracenter transition. Combining electron paramagnetic resonance and photoluminescence spectroscopy, we show that the NV−center in 3C-SiC has a ZPL line at 1.468 μm in excellent agreement with theoretical predictions. The ZPL line can be observed up to T=100 K. The negatively charged NV center in 3C-SiC is the structural isomorphe of the NV center in diamond and has equally a spin S=1 ground state and a spin S=1 excited state, long spin lattice relaxation times and presents optically induced groudstate spin polarization. These properties make it already a strong competitor to the NV center in diamond, but as its optical domain is shifted in the near infrared at 1.5μm, the NV center in 3C-SiC is compatible with quantum photonic networks and silicon based microelectronics. Published version

The creation of free excitons by absorption of circularly polarized photons, and their subsequent fast capture by donors, is at the origin of the spin polarization of donor-bound electrons. The sign of the electronic spin polarization at low density of excitation is, as expected, fixed by the helicity of the exciting light; but at high density of excitation we show that the spin polarization is of the opposite sign. This striking inversion is explained, here, by the contribution of dark excitons to mechanisms of spin polarization of localized electrons., 3 figures

We show that optical pumping of electron spins in individual InGaAs quantum dots leads to strong nuclear polarisation that we measure via the Overhauser shift (OHS) in magneto-photoluminescence experiments between 0 and 4T. We find a strongly non-monotonous dependence of the OHS on the applied magnetic field, with a maximum nuclear polarisation of 40% for intermediate magnetic fields. We observe that the OHS is larger for nuclear fields anti-parallel to the external field than in the parallel configuration. A bistability in the dependence of the OHS on the spin polarization of the optically injected electrons is found. All our findings are qualitatively understood with a model based on a simple perturbative approach., Comment: Phys Rev B (in press)