Saddle-point Van Hove singularities in the topological surface states are interesting because they can provide a new pathway for accessing exotic correlated phenomena in topological materials. Here, based on first-principles calculations combined with a kp model Hamiltonian analysis, we show that the layered platinum mineral jacutingaite (Pt₂HgSe₃) harbors saddlelike topological surface states with associated Van Hove singularities [1]. Pt₂HgSe₃ is shown to host two distinct types of nodal lines without spin-orbit coupling (SOC), which are protected by combined inversion (I) and time-reversal (T ) symmetries. Switching on the SOC gaps out the nodal lines and drives the system into a topological state with nonzero weak topological invariant Z₂ = (0; 001) and mirror Chern number n_M = −2. Surface states on the naturally cleaved (001) surface are found to be nontrivial with a unique saddle-like energy dispersion with type II Van Hove singularities. Our results indicate that Pt₂HgSe₃ is an ideal candidate material for exploring the properties of topological insulators with saddle-like surface states.


[1] B.Ghosh et.al, Physical Review B 100, 235101 (2019)