We studied the linear electro-optic effect of chiral topological semimetal RhSi which is characterized by high-fold chiral fermions separated in energy space. We identify that the general second order conductivity σxyz(2)(ω=ω1+ω2;ω1,ω2) includes a real symmetric component and an imaginary antisymmetric component, which are from the inter-band shift and intra-band injection current with frequency ω, respectively. The σxyz(2) is significantly enhanced by the high electron velocity and nontrivial band topology of chiral fermion, and modifies the phase velocity of light wave. We also predict that the electro-optic coefficient χxyz(2)(ω;ω,0) of chiral crystal RhSi is about 7000 pm/V at photon energy 0.01 eV and 1.1 eV, which is about 200 times that of widely used LiNbO3 crystal. The giant electro-optic coefficient renders a relatively low half-wave voltage in order of hundreds volt, and demonstrates potential application as electro-optic crystals for the wavelength in the second telecom window of optical fiber communications.
@article{arxiv.2110.11649,
title = {Giant electro-optic effect in chiral topological semimetal RhSi},
author = {Zhi Li and Yuewen Gao and Yu Gu and Shengli Zhang and Toshiaki Iitaka and W. M. Liu},
journal= {arXiv preprint arXiv:2110.11649},
year = {2021}
}