Excitons in hexagonal boron nitride single-layer: a new platform for polaritonics in the ultraviolet

Abstract

The electronic and optical properties of 2D hexagonal boron nitride are studied using first principle calculations. GW and Bethe–Salpeter equation (BSE) methods are employed in order to predict with better accuracy the excited and excitonic properties of this material. We determine the values of the band gap (7.32 eV, indirect), optical gap (5.58 eV), and excitonic binding energies (2.19 eV) and analyze the excitonic wave functions. We also calculate the exciton energies following an equation of motion formalism and the Elliot formula and find good agreement with the 𝐺𝑊+BSE method. The optical properties are studied for the TM and TE modes, showing that 2D hexagonal boron nitride (hBN) is a good candidate for polaritonics in the UV range. In particular, it is shown that a single layer of hBN can act as an almost perfect mirror for ultraviolet electromagnetic radiation.