Exciton interference in hexagonal boron nitride

Abstract

In this letter we report a thorough analysis of the exciton dispersion in bulk hexagonal boron nitride. We solve the ab initio GW Bethe-Salpeter equation at finite $\mathbf{q}\parallel \Gamma K$, and we compare our results with recent high-accuracy electron energy loss data. Simulations reproduce the measured dispersion and the variation of the peak intensity. We focus on the evolution of the intensity, and we demonstrate that the excitonic peak is formed by the superposition of two groups of transitions that we call $KM$ and $M{K}^{\prime }$ from the k-points involved in the transitions. These two groups contribute to the peak intensity with opposite signs, each damping the contributions of the other. The variations in number and amplitude of these transitions determine the changes in intensity of the peak. Our results contribute to the understanding of electronic excitations in this systems along the $\Gamma K$ direction, which is the relevant direction for spectroscopic measurements. They also unveil the non-trivial relation between valley physics and excitonic dispersion in h--BN, opening the possibility to tune excitonic effects by playing with the interference between transitions. Furthermore, this study introduces analysis tools and a methodology that are completely general. They suggest a way to regroup independent-particle transitions which could permit a deeper understanding of excitonic properties in any system.

References in corpus (3)

• Origin of the excitonic recombinations in hexagonal boron nitride by spatially resolved cathodoluminescence spectroscopy
• Direct Observation of the Lowest Indirect Exciton State in the Bulk of Hexagonal Boron Nitride
• Excitons in van der Waals materials: from monolayer to bulk hexagonal boron nitride

Cited by in corpus (13)

• Bright luminescence from indirect and strongly bound excitons in hBN
• Exciton-Phonon Interaction and Relaxation Times from First Principles
• Direct and indirect excitons in boron nitride polymorphs: a story of atomic configuration and electronic correlation
• Deep-ultraviolet electroluminescence and photocurrent generation in graphene/hBN/graphene heterostructures
• Theory of phonon-assisted luminescence in solids: application to hexagonal boron nitride
• Van der Waals epitaxy of two-dimensional single-layer h-BN on graphite by molecular beam epitaxy: Electronic properties and band structure
• Two-photon absorption in two-dimensional materials: The case of hexagonal boron nitride
• Phonon-assisted luminescence in defect centers from many-body perturbation theory
• Giant exciton-phonon coupling and zero-point renormalization in hexagonal monolayer boron nitride
• Bridging nano-optics and condensed matter formalisms in a unified description of inelastic scattering of relativistic electron beams
• Mapping of the energetically lowest exciton in bulk $1T$-HfS${}_2$
• Excitons under strain: light absorption and emission in strained hexagonal boron nitride
• Pressure Dependence of Electronic, Vibrational and Optical Properties of wurtzite-Boron Nitride