Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride
Physical Review B 83, 081413 (2011)
Anisotropic excitonic effects in the energy loss function of hexagonal boron nitride
We have studied the valence excitations in single-crystal hexagonal boron nitride (hBN) using inelastic X-ray scattering and ab-initio calculations. The energy-loss function displays a strong anisotropy both in shape, excitation energy and dispersion for momentum transfer q parallel or perpendicular to the hBN layers. The difference between the measured loss function for parallel/perpendicular momentum transfer translates into an energy shift of 0.7eV that cannot be captured by single-particle approaches and is a manifestation of a strong anisotropy in the two-body electron-hole interaction. Furthermore, we resolve the dependence of the loss function for the different in-plane directions of q. One of the dominant differences is a splitting of the π-plasmon in the G-M direction which is absent in the G-K direction and can be explained in terms of the h-BN band-structure.
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- http://dx.doi.org/10.1103/PhysRevB.83.081413
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- http://arxiv.org/abs/1005.0930