Flat Bands and Giant Light-Matter Interaction in Hexagonal Boron Nitride,Physical Review Letters

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Flat Bands and Giant Light-Matter Interaction in Hexagonal Boron Nitride
Physical Review Letters ( IF 8.1 ) Pub Date : 2021-09-23 , DOI: 10.1103/physrevlett.127.137401
C Elias ₁ , G Fugallo ₂ , P Valvin ₁ , C L'Henoret ₁ , J Li ₃ , J H Edgar ₃ , F Sottile ₄ , M Lazzeri ₅ , A Ouerghi ₆ , B Gil ₁ , G Cassabois ₁

Affiliation

Dispersionless energy bands in

k

space are a peculiar property gathering increasing attention for the emergence of novel electronic, magnetic, and photonic properties. Here, we explore the impact of electronic flat bands on the light-matter interaction. The van der Waals interaction between the atomic layers of hexagonal boron nitride induces flat bands along specific lines of the Brillouin zone. The macroscopic degeneracy along these lines leads to van Hove singularities with divergent joint density of states, resulting in outstanding optical properties of the excitonic states. For the direct exciton, we report a giant oscillator strength with a longitudinal-transverse splitting of 420 meV, a record value, confirmed by our ab initio calculations. For the fundamental indirect exciton, flat bands result in phonon-assisted processes of exceptional efficiency, that compete with direct absorption in reflectivity, and that make the internal quantum efficiency close to values typical of direct band gap semiconductors.

中文翻译：

六方氮化硼中的平带和巨大的光物质相互作用

无色散能带

克

空间是一种奇特的特性，随着新的电子、磁和光子特性的出现而引起越来越多的关注。在这里，我们探讨了电子平带对光-物质相互作用的影响。六方氮化硼原子层之间的范德华相互作用导致沿布里渊区特定线的平坦带。沿着这些线的宏观简并导致范霍夫奇点具有不同的联合态密度，从而导致激子态的出色光学特性。对于直接激子，我们报告了一个巨大的振荡器强度，纵向 - 横向分裂为 420 meV，这是一个记录值，由我们的ab initio证实计算。对于基本的间接激子，平带导致具有卓越效率的声子辅助过程，这与反射率的直接吸收竞争，并使内部量子效率接近直接带隙半导体的典型值。

更新日期：2021-09-23

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