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HL: Fachverband Halbleiterphysik
HL 35: Optical Properties II
HL 35.8: Vortrag
Mittwoch, 11. März 2026, 18:30–18:45, POT/0251
Role of lattice temperature for the optical properties of boron nitride — •Peter Kratzer1 and Andre Schleife2 — 1Faculty of Physics, University Duisburg-Essen, 47057 Duisburg, Germany — 2Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
We carried out a computational study of boron nitride both in its cubic (c-BN) and hexagonal (h-BN) polytypes as a prototypical system for the renormalization of optical properties in semiconductors by lattice vibrations. While band-gap renormalization due to electron-phonon coupling is a well-explored concept in semiconductor physics, this topic has gained renewed attention in the context of pump-probe spectroscopies where high fluences may lead to local lattice excitation. With this motivation, we performed first-principles calculations of c-BN and h-BN supercells using the DFT+GW method, treating lattice excitation via explicit atomic displacements. Finally, the frequency-dependent dielectric function and the optical absorbance are obtained including many-particle effects on the level of the Bethe-Salpeter equation. The results show that the atomic displacements in the 2x2x2 supercells used in this study have little effect in c-BN but lead to a considerable narrowing of the optical gap in h-BN. In h-BN, the band splitting due to 'frozen' phonons gets even amplified on the GW level of theory. The binding energy of approximately 0.5eV of the exciton derived from the band edges, however, is found to be only weakly affected by the atomic displacements.
Financial support from CRC 1242 is gratefully acknowledged.
Keywords: boron nitride; GW calculations; Bethe-Salpeter equation; band gap renormalization; electron-phonon coupling