Exciton energy-momentum map of hexagonal boron nitride

Abstract

Understanding and controlling the way excitons propagate in solids is a key for tailoring materials with improved optoelectronic properties. A fundamental step in this direction is the determination of the exciton energy-momentum dispersion. Here, thanks to the solution of the parameter-free Bethe- Salpeter equation (BSE), we draw and explain the exciton energy-momentum map of hexagonal boron nitride (h-BN) in the first three Brillouin zones. We show that h-BN displays strong excitonic effects not only in the optical spectra at vanishing momentum $\mathbf{q}$, as previously reported, but also at large $\mathbf{q}$. We validate our theoretical predictions by assessing the calculated exciton map by means of an inelastic x-ray scattering (IXS) experiment. Moreover, we solve the discrepancies between previous experimental data and calculations, proving then that the BSE is highly accurate through the whole momentum range. Therefore, these results put forward the combination BSE and IXS as the tool of choice for addressing the exciton dynamics in complex materials.

References in corpus (1)

• First-principles method of propagation of tightly bound excitons: exciton band structure of LiF and verification with inelastic x-ray scattering

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• Excitons in van der Waals materials: from monolayer to bulk hexagonal boron nitride
• Angular resolved electron energy loss spectroscopy in hexagonal boron nitride
• Two-photon absorption in two-dimensional materials: The case of hexagonal boron nitride
• Cubic BN optical gap and intragap optically active defects
• Exciton interference in hexagonal boron nitride
• Non-invasive control of excitons in two-dimensional materials
• High Performance Solution of Skew-symmetric Eigenvalue Problems with Applications in Solving the Bethe-Salpeter Eigenvalue Problem