Current-induced second harmonic generation in inversion-symmetric Dirac and Weyl semimetals

Second harmonic generation (SHG) is a fundamental nonlinear optical phenomenon widely used both for experimental probes of materials and for application to optical devices. Even-order nonlinear optical responses including SHG generally require breaking of inversion symmetry, and thus have been utilized to study noncentrosymmetric materials. In this talk, we will talk about our theoretical study of the SHG in inversion-symmetric Dirac and Weyl semimetals under a DC current which breaks the inversion symmetry by creating a nonequilibrium steady state [1]. We find that Dirac and Weyl semimetals exhibit strong SHG upon application of finite current. Our experimental estimation for a Dirac semimetal Cd₃As₂ and a magnetic Weyl semimetal Co₃Sn₂S₂ suggests that the induced susceptibility χ⁽²⁾ for practical applied current densities can reach 10⁵ pm V⁻¹ with mid-IR or far-IR light. This value is 100-10000 times larger than those of typical nonlinear optical materials.

[1] KT, T. Morimoto, J. Orenstein, and J. E. Moore, arXiv:2007.08887.