Berlin 2024 – scientific programme

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QI: Fachverband Quanteninformation

QI 25: Materials and Devices for Quantum Technology II (joint session HL/QI)

QI 25.4: Talk

Thursday, March 21, 2024, 15:00–15:15, EW 203

Theory of optical ionization of Silicon Vacancies in 4H-SiC — •Maximilian Schober and Michel Bockstedte — Institute for Theoretical Physics, Johannes Kepler University Linz, Altenbergerstr. 69, A-4040 Linz, Austria

The Silicon Vacancy (VSi) in 4H-SiC represents a quantum bit with advantageous properties for applications like quantum sensing and as a single-photon emitter. Optical readout of its spin state is achieved via a spin-selective optical cycle enabled by coupled defect electron spins and associated spin-dependent interactions. An alternative readout method involves spin-to-charge conversion through optical ionization [1] of the qubit, followed by the electrical detection of the resulting spin-sensitive photocurrents. Relatively little is known, however, regarding the photophysics of the optically silent charge states of VSi created throughout this process. To tackle this issue, we investigate such systems with a combined ab initio framework of density functional theory and CI-cRPA [2] capable of including the crucial multiplet physics of such qubit centers. We discuss the relevant single and two-photon processes for optical charge state switching and electrical detection of the spin states. Furthermore, we shine light on the nominally "dark" neutral and doubly negatively charged centers as potential infrared emitters.

[1] M. Niethammer et al., Nat Commun 10, 5569 (2019).

[2] M. Bockstedte et al., npj Quant Mater 3, 31 (2018).

Keywords: spin defect qubit; charge state control; spin-to-charge conversion; correlated states; ab initio theory