The impact of strain on the GeV-color center in diamond

Abstract

Color centers in diamond, such as the GeV center, are promising candidates for quantum-based applications. Here, we investigate the impact of strain on the zero-phonon line (ZPL) position of GeV. Both hydrostatic and linear strain are modeled using density functional theory for GeV concentrations of 1.61 % down to 0.10 %. We present qualitative and quantitative differences between the two strain types: for hydrostatic tensile and compressive strain, red- and blue-shifted ZPL positions are expected, respectively, with a linear relation between the ZPL shift and the experienced stress. By calculating the ZPL shift for varying GeV concentrations, a shift of 0.15 nm/GPa (0.38 meV/GPa) is obtained at experimentally relevant concentrations using a hybrid functional. In contrast, only red-shifted ZPL are found for tensile and compressive linear strain along the direction. The calculated ZPL shift exceeds that of hydrostatic strain by at least one order of magnitude, with a significant difference between tensile and compressive strains: 3.2 and 4.8 nm/GPa (8.1 and 11.7 meV/GPa), respectively. In addition, a peak broadening is expected due to the lifted degeneracy of the GeV state, calculated to be about 6 meV/GPa. These calculated results are placed in perspective with experimental observations, showing values of ZPL shifts and splittings of comparable magnitude.