BaAs2: an arsenide with giant second harmonic generation enabled by interesting As–As bonds

Abstract

The second harmonic generation (SHG) response of BaAs₂, which features As–As bonds beneficial for the nonlinear optical (NLO) properties, was reported for the first time in this work. BaAs₂ crystallizes in the monoclinic Pc space group with a non-centrosymmetric (NCS) structure, and it is a direct band gap semiconductor material with a band gap of 0.77 eV. The SHG measurements show that the SHG intensity of BaAs₂ is 1.2 times that of CdGeAs₂. Theoretical calculations indicate that the NLO effect of BaAs₂ mainly originates from the [As⁻] chains, and its maximum second-order NLO coefficient is 146.02 pm V⁻¹.