Bulk and Surface Electronic Structure of the Dual-Topology Semimetal Pt2HgSe3

Abstract

We report high-resolution angle resolved photoemission measurements on single crystals of Pt2HgSe3 grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001)-projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial k-space range we find surface states with multiple saddle-points in the dispersion resulting in two van Hove singularities in the surface density of states. Based on density functional theory calculations, we identify these surface states as signatures of a topological crystalline state which coexists with a weak topological phase.

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

“…at a low-symmetry point between Γ and M), in perfect agreement with current ARPES measure- ments [16]. Notably, the model also exhibits 001-surface states that roughly span the same BZ region as observed in experiments [16], thus providing a remarkably realistic qualitative description of the system, despite its simplicity. An interesting feature of the J3KM model that helps to rationalize the presence of surface states is that, at a given parallel momentum k = (k x , k y ), it is equivalent to a k -dependent 1D tight-binding Hamiltonian analogous to the Su-Schrieffer-Heeger (SSH) one, where the alternating hopping energies,t(k ) andt 2 (k ), between intralayer and interlayer neighboring sites of a Hg chain depend parametrically on k (see Fig.…”

“…For λ = 1 (corresponding to bulk jacutingaite), in addition to the graphene-like Dirac states at K, such simple model accounts for the presence of additional linear crossings between valence and conduction bands (e.g. at a low-symmetry point between Γ and M), in perfect agreement with current ARPES measure- ments [16]. Notably, the model also exhibits 001-surface states that roughly span the same BZ region as observed in experiments [16], thus providing a remarkably realistic qualitative description of the system, despite its simplicity.…”

“…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].…”

“…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]. The unexpected dual topology of bulk jacutingaite cannot be understood through the standard paradigm of weak topological insulators [17] and its interpretation opens interesting perspectives on non-trivial extensions of the KM model to describe 3D stacks of honeycomb layers.…”

“…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].…”