LAUSR

The discovery of new types of metal sulfides is attractive because of their rich structures and diverse physical properties. Here, a novel quaternary sulfide, Ba3HgGa2S7 (BHGS), is obtained by a solid-state reaction at 1123 K. It crystallizes in the monoclinic space group P21/c, and its zero-dimensional structure features two seesaw-like HgS2 units and four GaS4 tetrahedra, constructing a unique [Hg2Ga4S14]12- string. BHGS has a wide band gap of 3.64 eV and a large birefringence of 0.09 at 2100 nm. Specifically, BHGS exhibits a remarkable photocurrent response. This work may be extended to a new family of AE3MIIMIII2Q7 (AE = Mg, Ca, Sr, Ba; MII = Zn, Cd, Hg; MIII = Al, Ga, In; Q = S, Se) chalcogenides.