Pnictide square net materials with reduced symmetry, the rare earth diantimonides: electronic structure and topology

With the discovery of Dirac fermions, much research effort has been put into finding the structural elements that can generate Dirac-like degeneracies in the electronic band structures [1]. It was discovered that some layered materials can host planar square nets of group IV-V elements within their lattice. Analogously to graphene, these square nets possess a 2-atom basis and feature wide Dirac bands. Most of the known layered compounds that retain the electronic properties of the net, such as (Sr,Ca)MnBi₂ and ZrSiS, crystallize in a tetragonal structure, and exhibit a Dirac semimetal or nodal line phase that can host a rich plethora of electronic and magnetic quantum properties [2]. In this talk we will show a new variety of square net semimetals whose structure breaks the 4-fold symmetry, the rare earth di-antimonides. These materials crystallize in the orthorhombic group Cmca reducing the overall symmetry of the system. We employed ARPES and DFT calculations on the series precursor, LaSb₂, to study its electronic structure. We will discuss the effect that the symmetry reduction has on the electronic properties, on the Dirac states, as well as its interplay with spin-orbit coupling.
[1] B. Bradlyn et al., Nature 547, 298 (2017)
[2] S. Klemenz et al., Arxiv:1808.06619v1 (2018)