We proposed that BaHgSn is a Dirac semimetal (DSM) which can host hourglass-like surface states (HSSs) as protected by nonsymmorphic glide symmetry. Compared to KHgSb, an isostructural topological crystalline insulator with the same HSSs, BaHgSn has an additional band inversion at Γ point. This band inversion is induced by the stronger interlayer coupling among Hg-Sn honeycomb layers than that among Hg-Sb-layers in KHgSb, which leads to bulk Dirac nodes in BaHgSn along the layer stacking direction Γ-A. In addition, the mirror Chern number Ci protected by the mirror plane Mz (kz=0) changes from 2 in KHgSb to 3 in BaHgSn. Therefore, when a compressive uniaxial strain is applied along the y axis to break the rotation symmetry protecting the DSM state, BaHgSn becomes a strong topological insulator with Z2 indices of (1;000) and the topological surface Dirac cone co-exists with HSSs on the (010) surface. The Wilson-loop spectra have been calculated to verify these topological features. The calculated surface states, the Fermi surfaces and their quasiparticle interference patterns are ready to be compared with experimental measurements.
@article{arxiv.1912.00599,
title = {BaHgSn: A Dirac semimetal with surface hourglass fermions},
author = {Tan Zhang and Zhihai Cui and Zhijun Wang and Hongming Weng and Zhong Fang},
journal= {arXiv preprint arXiv:1912.00599},
year = {2020}
}