Temperature-Dependent Spectral Properties of Hexagonal Boron Nitride Color Centers

Color centers in hexagonal boron nitride (hBN) are emerging as a mature platform for single-photon sources in quantum technology applications. In this study, we investigate the temperature-dependent spectral properties of a single defect in hBN to understand the dominant dephasing mechanisms due to phonons. We observe a sharp zero-phonon line (ZPL) emission accompanied by Stokes and anti-Stokes optical phonon sidebands assisted by the Raman-active low-energy (≈ 6.5 meV) interlayer shear mode of hBN. The shape of the spectral lines around the ZPL is measured down to 78 K, at which the line width of the ZPL is measured as 211 μeV. Using a quadratic electron–phonon interaction, the temperature-dependent broadening and the lineshift of the ZPL are found to follow a temperature dependence of T + T⁵ and T + T³, respectively. Furthermore, the temperature-dependent line shape around the ZPL at low-temperature conditions is modeled with a linear electron–phonon coupling theory, which results in a 0 K Debye–Waller factor of the ZPL emission as 0.59. Our results provide insights into the underlying mechanisms of electron–phonon coupling in hBN, which is critical to enhance their potential for applications in quantum technologies.