A highly distorted HgS4 tetrahedron-induced moderate second-harmonic generation response of EuHgGeS4

Abstract

A quaternary Eu-based sulfide EuHgGeS₄ has been synthesized by a high-temperature solid-state reaction. It crystallizes in the noncentrosymmetric orthorhombic space group Ama2 and features highly distorted HgS₄ tetrahedra. It exhibits phase-matchable second-harmonic generation (SHG) behavior and an intensity of around 0.9 times that of AgGaS₂. Theoretical calculations on its electronic structure and optical properties are performed and the results are well consistent with the experimental findings. Structural analysis suggests that the HgS₄ tetrahedron plays an important role in the SHG activity.