Double Resonant Tunable Second Harmonic Generation in Two-dimensional Layered Materials through Band Nesting

TL;DR

This paper proposes a mechanism for giant, tunable second harmonic generation in layered materials by engineering electronic band structures to achieve double resonance, demonstrated theoretically in bilayer SnS.

Contribution

It introduces a novel band engineering approach to enhance nonlinear optical responses via double resonance in 2D materials.

Findings

Giant second harmonic susceptibility achieved in bilayer SnS

Electrical bias tuning maximizes nonlinear response

Polarization anisotropy tunability enables new devices

Abstract

We proposed a mechanism to generate giant anisotropic second harmonic nonlinear response via double resonance effect, achieved through band nesting via electronic bandstructure engineering. The ideal band setup would be a triplet of nested bands separated by the fundamental resonance energy, $\hbar\omega$. We demonstrate theoretically that the proposed phenomenon can be realized in bilayer SnS by band tuning with perpendicular electrical bias, which maximizes the second harmonic susceptibility by several orders of magnitude. Moreover, the tunability of the polarization anisotropy can be useful for realizing novel polarization-sensitive devices.