Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 51: 2D Materials: Session III (joint session DS/CPP/HL)
HL 51.6: Talk
Friday, March 16, 2018, 11:15–11:30, H 2032
Disclosing the nature of excitons in van der Waals materials: The role of layer stacking in hexagonal boron nitride — Wahib Aggoune1,2, •Caterina Cocchi2,3, Dmitrii Nabok2,3, Karim Rezouali1, Mohamed Akli Belkhir1, and Claudia Draxl2,3 — 1Laboratoire de Physique Théorique, Faculté des Sciences Exactes, Université de Bejaia, 06000 Bejaia, Algeria — 2Institut fur Physik and IRIS Adlershof, Humboldt-Universitat zu Berlin, Berlin, Germany — 3European Theoretical Spectroscopic Facility (ETSF)
With the example of bulk hexagonal boron-nitride, a prototypical van der Waals (vdW) crystal, we demonstrate that the electronic and optical properties of these materials can be tuned by layer patterning. By modifying the stacking, energy, intensity, and character of the electron-hole (e-h) pairs can be selectively modulated. Depending on the specific layer arrangement, lowest-energy excitons are localized within a single layer or delocalized in the three-dimensional space. Only in specific stackings charge-transfer e-h pairs appear above the absorption onset, triggered by the spatial distribution of the electronic states involved. Our results, obtained within a first-principles many-body framework, provide all the ingredients to identify, predict, and tailor the character of the e-h pairs in vdW materials.