Examining the Effect of Charge Density Waves on the Electronic Structure of LnSbTe-type Systems.

The square-net structure, as found in the LnSbTe family (Ln = lanthanides), exhibits symmetry-enforced band crossings near the Fermi level, making these materials topological semimetals. Adding spin-orbit coupling gaps the band structure into a topologically insulating phase. When these square nets are slightly distorted the system's symmetry is lowered, often allowing band crossings to gap out. Different square-net symmetries can be broken by the many charge density waves that are observed in Sb and Te square nets. This provides a promising platform to explore the relationship between the topology and symmetry of the distorted square-net system. We use tight-binding models to investigate the effect of these charge density wave distortions on the topological states of square-net compounds and discuss the real-space bonding relationship between these states.