Effect of Localization on Photoluminescence and Zero-Field Splitting of Silicon Color Centers

Abstract

The study of defect centers in silicon has been recently reinvigorated by their potential applications in optical quantum information processing. A number of silicon defect centers emit single photons in the telecommunication O-band, making them promising building blocks for quantum networks between computing nodes. The two-carbon G-center, self-interstitial W-center, and spin-1/2 Tcenter are the most intensively studied silicon defect centers, yet despite this, there is no consensus on the precise configurations of defect atoms in these centers, and their electronic structures remain ambiguous. Here we employ ab initio density functional theory to characterize these defect centers, providing insight into the relaxed structures, bandstructures, and photoluminescence spectra, which are compared to experimental results. Motivation is provided for how these properties are intimately related to the localization of electronic states in the defect centers. In particular, we present the calculation of the zero-field splitting for the excited triplet state of the G-center defect as the structure is transformed from the A-configuration to the B-configuration, showing a sudden increase in the magnitude of the Dzz component of the zero-field splitting tensor. By performing projections onto the local orbital states of the defect, we analyze this transition in terms of the symmetry and bonding character of the G-center defect which sheds light on its potential application as a spin-photon interface.

Midgap state requirements for optically active quantum defects

“…To illustrate the mismatch between the often-stated need for defect levels far from the band edges and the characteristics of actual quantum defects, we revisit the electronic structure of four representative defects: the NV center [10,37] and Si split-vacancy [38,39] in diamond, as well as the selenium substitutional defect [40,41] and T center in silicon [11,12,42,43]. These defects have well-characterized atomic structure and have already shown promise as spin-photon interfaces.…”

Phonon Induced Spin Dephasing Time of Nitrogen Vacancy Centers in Diamond from First Principles

“…In the rest of the paper we will focus on the evaluation of spin dephasing times in the nitrogen vacancy center using constrained Density Functional Theory [43][44][45] (cDFT) based calculations. These methods are routinely employed now to study the electronic structure of defects embedded in solids 4,46,47 . We use the cumulant expansion approximation to obtain the dephasing function.…”