We theoretically study point defects in 3C-SiC for applications in Quantum Technologies, focusing on the neutral silicon vacancy, with an electron spin of 1, magnetically interacting with the SiC nuclear spin bath containing Si-29 and C-13 nuclei. Initially, the system's energetics are explored with ab-initio methods based on the Density Functional Theory. Thereon, we apply a Hahn-echo sequence on the electron spin and study the effects of the bath dynamics on the electron spin's coherence. The Electron Spin Echo Envelope Modulation (ESEEM) phenomenon, due to single nuclear spin flipping processes, and the overall decay, or decoherence, due to the electron spin's entanglement with the bath, are examined. We exploit the Cluster Correlation Expansion (CCE) theory for calculating an approximate version of the coherence function, at various orders of approximation, in order to associate the different coherence function behaviors to given n-body correlations within the bath.
[Formula: see text]/AlGaN metal-oxide-semiconductor capacitors show a hysteretic behavior in their capacitance vs voltage characteristics, often attributed to near-interface traps deriving from defects within the oxide layer. The origin as well as the structural/electronic properties of such defects are still strongly debated in the literature. Here, we use ab initio molecular dynamics and the climbing-image nudged elastic band method to show that aluminum Frenkel defects give rise to bistable trap states in disordered and stoichiometric [Formula: see text]. Based on these results, we propose a calibrated polaron model representing a distribution of individually interacting energy levels with an internal reconfiguration mode and coupled to continuous bands of carriers to explain the hysteresis mechanism in [Formula: see text]/AlGaN capacitors.
We study the silicon vacancy in 3C-SiC as a color center of interest in the field of Quantum Technologies, focusing on its magnetic interaction with the SiC nuclear spin bath containing Si 29 and C 13 nuclei in their natural isotopic concentration. We calculate the system's energetic and magnetic properties with ab initio methods based on the Density Functional Theory, identifying the neutral charge state of the silicon vacancy as the most favorable for p-doped 3C-SiC systems. We thereon evaluate the Free Induction Decay and the Hahn-echo sequence on the electron spin interacting with the nuclear spin bath. Here, the Electron Spin Echo Envelope Modulation phenomenon, due to single nuclear spin flipping processes, and the overall decay are highlighted in the context of the Cluster Correlation Expansion theory. We find a non-exponential coherence decay, which is a typical feature of solid-state qubits subjected to low frequency 1/f-type noise from the environment.
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