Zusammenfassung
In this manuscript we study luminescence of hexagonal boron nitride (hBN) by
means of non-equilibrium Green's functions plus time-dependent perturbation
theory. We derive a formula for light emission in solids in the limit of a weak
excitation that includes perturbatively the contribution of electron-phonon
coupling at the first order. This formula is applied to study luminescence in
bulk hBN. This material has attracted interest due to its strong luminescence
in the ultraviolet Watanabe et al., Nature Mat. 3, 404(2004). The origin of
this luminescence has been widely discussed, but only recently has a clear
signature of phonon mediated light emission emerged in the experiments
Cassabois et al., Nature Phot. 10, 262(2016). By means of our new theoretical
approach we provide a clear and full explanation of light emission in hBN.
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