Second-harmonic generation in the topological multifold semimetal RhSi

Recent experiments in the topological Weyl semimetal TaAs have observed record-breaking second-harmonic generation, a non-linear optical response at $2\omega$ generated by an incoming light source $\omega$. However, whether generation is enhanced semimetals general challenging open question because their band structure entangles contributions arising from trivial bands and crossings. In this work, we circumvent problem studying RhSi, chiral with simple multifold fermions close to Fermi energy. We measure (SHG) wide frequency window, $\omega\in [0.27,1.5]$eV and, using first principle calculations, establish that, due linear dispersion, contribution of SHG subdominant as compared other regions Brillouin zone. Our calculations suggest that parts where dispersion relatively flat contribute significantly SHG. As whole, our results avenues enhance responses.