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Exciton-Enhanced Spontaneous Parametric Down-Conversion in Two-Dimensional Crystals (2305.08345v3)
Published 15 May 2023 in physics.comp-ph and cond-mat.mtrl-sci
Abstract: We show that excitonic resonances and interexciton transitions can enhance the probability of spontaneous parametric down-conversion, a second-order optical response which generates entangled photon pairs. We benchmark our ab initio many-body calculations using experimental polar plots of second harmonic generation in NbOI$_2$, clearly demonstrating the relevance of excitons in the nonlinear response. A strong double-exciton resonance in 2D NbOCl$_2$ leads to giant enhancement in the second order susceptibility. Our work paves the way for the realization of efficient ultrathin quantum light sources.