Saddle-point Van Hove singularity and dual topological state in Pt2HgSe3

Abstract

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 k · p model Hamiltonian analysis, we show that the layered platinum mineral jacutingaite (Pt2HgSe3) harbours saddle-like topological surface states with associated van Hove singularities. Pt2HgSe3 is shown to host two distinct types of nodal lines without spin-orbit coupling (SOC) which are protected by combined inversion (I) and timereversal (T ) symmetries. Switching on the SOC gaps out the nodal lines and drives the system into a topological insulator state with nonzero weak topological invariant Z2 = (0; 001) and mirror Chern number nM = 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. We also discuss how modulating the crystal structure can drive Pt2HgSe3 into a Dirac semimetal state with a pair of Dirac points. Our results indicate that Pt2HgSe3 is an ideal candidate material for exploring the properties of topological insulators with saddle-like surface states.

Emergent dual topology in the three-dimensional Kane-Mele Pt2HgSe3

“…Indeed, by computing the energy bands of the J3KM model without SOC we uncover the presence of a nodal line (see Fig. 3c) dispersing across the border of the reduced BZ -also predicted by firstprinciples simulations [15,16]-whose projection on the parallel plane is consistent with the boundary between regions with topologically distinct Zak phases [29].…”

“…Being a stacking of 2D QSHIs, bulk jacutingaite is expected to be a 3D weak topological insulator with indices (0; 001), and thus with no surface states on the (001) surface [17]. Recent first-principles simulations confirmed this weak topological classification [14][15][16], but at the same time surprisingly predicted the presence of basal surface states associated with a non-trivial mirror Chern number, thus promoting bulk jacutingaite to a dual topological material [18,19] with both weak and crystalline topological properties. Such (001) surface states have now been demonstrated independently through angleresolved photoemission spectroscopy (ARPES) experiments on synthetic jacutingaite single crystals [16].…”

“…Although jacutingaite is a ternary material with several differences with respect to the Xenes, it shares a (buckled) honeycomb structure of mercury atoms (see Fig. 1a), which is ultimately responsible for the KM physics in monolayers [9] that sparked experimental [12] and theoretical [13][14][15][16] interest in this material.…”

Bridging the Gap between H- and J-Aggregates: Classification and Supramolecular Tunability for Excitonic Band Structures in 2-Dimensional Molecular Aggregates

“…graphene), this is known to cause superconductivity, topological insulators and other exotic phenomena. [33][34][35] In case of the molecular aggregates, position of the bright state relative to the VHPs can be useful in distinguishing Iaggregates from J-aggregates and ultimately, explaining many of the photophysical properties such as quantum yields, linewidths, temperature dependent shifts and transport properties.…”

Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2

“…A saddle point is closely related to a VHS, leading to a divergence in the density of states. Previously, VHSs have been reported in a variety of materials; graphene 13 , 14 , cuprate superconductors 15 – 17 , Pt 2 HgSe 3 18 , Pb 1− x Sn x Se(Te) 19 . The proximity of E F to a VHS is expected to significantly enhance the impact of electronic correlations and drive quantum many body instabilities toward superconductivity 20 – 22 ferromagnetism 23 – 26 or antiferromagnetism 27 , depending on band structure and many-body interactions.…”