Berry curvature in monolayer MoS2 with broken mirror symmetry

An ideal 1H phase monolayer MoS2 has mirror reflection symmetry, but this symmetry is broken in common experimental situations, where the monolayer is placed on a substrate. By using k·p perturbation theory, we investigate the effect of mirror symmetry breaking on the Berry curvature of the material. We find that the symmetry breaking may modify the Berry curvature considerably, and the spin/valley Hall effect due to modified Berry curvature is in qualitative agreement with a recent experimental result [Science 344, 1489 (2014)], which cannot be explained by previous theories that ignore mirror symmetry breaking.