High-resolution Fourier-transform photoluminescence spectroscopy combined with the resonant photoexcitation technique was used to study in detail the Zeeman eff'ect on excitons bound to the neutral donors in high purity epitaxial GaAs. The neutral donor g-factor depends on the magnetic-field intensity and orientation in agreement with the predictions of the five-level k p theory. The neutral-donor excited-state energies measured in a range of magnetic field from 0 to l2 T are in an excellent agreement with appropriately scaled calculations for the hydrogen atom. The correspondence between transitions having the same initial state but having as a final state either the nuetral-donor ground state (principal transitions) or a neutral donor excited state (two electron satellites) was established using resonant excitation and was verified by the angular dependences of the peak energies. Linear and circular polarizations of the 2p, 2po, and 2p+ two-electron satellites are consistent with the assignment of zero angular momentum to the ground state of the donor-bound exciton and we show that the transition energies for these components can be calculated with a 0.03-meV accuracy over the range from 0 to 12 T.

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Global quantum networks will benefit from the reliable creation and control of high-performance solid-state telecom photon-spin interfaces. T radiation damage centres in silicon provide a promising photon-spin interface due to their narrow O-band optical transition near 1326 nm and long-lived electron and nuclear spin lifetimes. To date, these defect centres have only been studied as ensembles in bulk silicon. Here, we demonstrate the reliable creation of high concentration T centre ensembles in the 220 nm device layer of silicon-on-insulator (SOI) wafers by ion implantation and subsequent annealing. We then develop a method that uses spin-dependent optical transitions to benchmark the characteristic optical spectral diffusion within these T centre ensembles. Using this new technique, we show that with minimal optimization to the fabrication process high densities of implanted T centres localized < ∼ 100 nm from an interface display ∼ 1 GHz characteristic levels of total spectral diffusion.

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We have carried out a high-resolution x-ray scattering study of the first-order paraelectric (PE) to ferroelectric (FE) transition of BaTi03. Using a pulsed electric field to cross the PE-FE phase boundary, both the x-ray scattering and bulk polarisation associated with the equilibrium FE phase appear only after a well defined delay relative to the pulse onset. Subsequently, the polarisation evolves much more rapidly than the x-ray intensity.