Resonant Structure of Second Harmonic Generation in Multilayer Graphene Polytypes.

Sarsfield, Patrick Johansen; Joya, Takaaki V; Kawakami, Takuto; Koshino, Mikito; Fal'ko, Vladimir · Nano Lett · 2026

basic_science · Level V

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Abstract

Second harmonic generation (SHG) is a powerful optical tool for identifying noncentrosymmetric crystalline structures. Here, we analyze SHG in multilayer graphenes (MLG), with a focus on its dependence on the stacking order, encapsulation environment, and biasing that break inversion symmetry in multilayers, as well as the SHG sensitivity to the electron-hole asymmetry in the MLG spectra and doping. In particular, we identify stacking-order-dependent resonant features in the SHG spectra for trilayers and tetralayers, suggesting that infrared-range SHG offers a noninvasive characterization method for distinguishing between MLG polytypes, as well as optical identification of crystallographic direction in MLG films.