Optical and magnetic properties of the T radiation damage centre in 28Si

Synopsis

Silicon underpins the most well-developed integrated photonics platform which, combined to an optically-efficient paramagnetic defect, would enable a wide range of integrated quantum technologies such as optically-linked qubits, photon memories, quantum transducers, and more. While many defects in silicon hold long-lived spin qubits, it remains difficult to use them as the base for a spin-photon interface, because they typically suffer from poor radiative efficiencies or have inconvenient optical transition energies. A number of silicon defects with transition wavelengths in the telecommunication bands are already known to exist, prominently from radiation damage centres.

Of special interest is the T centre, a paramagnetic defect thought to be made of two carbon atoms and one hydrogen atom along with an uncoupled electron in the ground state. In this first study of T centres in ²⁸Si, we measure a linewidth of 0.137(10) µeV for the transition to the first excitonic state, orders of magnitude sharper than in natural silicon (^natSi). This linewidth consists of an upper bound on the true single-centre linewidth even for ^natSi. From pulsed laser transient spectroscopy, we measure an excited state lifetime of 0.94(1) µs. Using photoluminescence excitation techniques, we show that resonant optical saturation leads to a dipole moment of 0.27(3) Debye and to a radiative efficiency of 13(3) %. Furthermore, experiments with an external magnetic field confirm that the excited state Zeeman splitting is anisotropic and reveal that the ground state electron spin has an anisotropic hyperfine interaction with the hydrogen nuclear spin, mediated by a coupling constant on the order of -3 MHz. We demonstrate that initialization, readout and control over both the electron spin and the nuclear spin are possible using magnetic resonance, and measure relaxation times greater than 16 s as well as coherence times of 2.1(1) ms for the electron spin and 1.1(2) s for the hydrogen nuclear spin.