Synthesis of stable gamma-phase MnS1-xSex nanoflakes with inversion symmetry breaking

Inversion symmetry breaking plays a critical role in the formation of magnetic skyrmions. Therefore, for the application of skyrmion-based devices, it is important to develop novel engineering techniques and explore new non-centrosymmetric lattices. In this paper, we report the rational synthesis of stable gamma-phase MnS1-xSex (0 <= x <= 0.45) nanoflakes with an asymmetric distribution of the elemental content, which persists on inversion symmetry breaking. The temperature dependence of resonant second-harmonic generation characterization reveals that a non-centrosymmetric crystal structure exists in our as-grown gamma-phase MnS1-xSex with spatial-inversion symmetry breaking. By tuning the parameters of nucleation temperature and growth time, we produced a detailed growth phase diagram, revealing a controllable as-grown structure evolution from gamma-phase wurtzite-type to alpha-phase rock-salt type structure of MnS1-xSex nanoflakes. Our work provides a new playground to explore novel materials that have broken inversion symmetry.