Nonsymmorphic-symmetry-protected hourglass Dirac loop, nodal line, and Dirac point in bulk and monolayer $X_3$SiTe${}_6$ ($X=$ Ta, Nb)

Abstract

Nonsymmorphic space group symmetries can generate exotic band-crossings in topological metals and semimetals. Here, based on symmetry analysis and first-principles calculations, we reveal rich band-crossing features in the existing layered compounds Ta${}_3$SiTe${}_6$ and Nb${}_3$SiTe${}_6$, enabled by nonsymmorphic symmetries. We show that in the absence of spin-orbit coupling (SOC), these three-dimensional (3D) bulk materials possess accidental Dirac loops and essential fourfold nodal lines. In the presence of SOC, there emerges an hourglass Dirac loop---a fourfold degenerate nodal loop, on which each point is a neck-point of an hourglass-type dispersion. We show that this interesting type of band-crossing is protected and dictated by the nonsymmorphic space group symmetries, and it gives rise to drumhead-like surface states. Furthermore, we also investigate these materials in the monolayer form. We show that these two-dimensional (2D) monolayers host nodal lines in the absence of SOC, and the nodal lines transform to essential spin-orbit Dirac points when SOC is included. Our work suggests a realistic material platform for exploring the fascinating physics associated with nonsymmorphic band-crossings in both 3D and 2D systems.

12 pages, 12 figures

References in corpus (16)

• Weyl semimetal phase in non-centrosymmetric transition metal monophosphides
• Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
• Classification of stable three-dimensional Dirac semimetals with nontrivial topology
• Topological Node-Line Semimetal in Three Dimensional Graphene Networks
• Topological nodal line semimetals
• Topological Semimetals
• Potential ring of Dirac nodes in a new polymorph of Ca${}_3$P${}_2$
• Line of Dirac Nodes in Hyper-Honeycomb Lattices
• Co-existence of size-dependent and size-independent thermal conductivities in single layer black phosphorus
• Dirac and Weyl Materials: Fundamental Aspects and Some Spintronics Applications
• Correlation and transport phenomena in topological nodal-loop semimetals
• Two-dimensional Spin-Orbit Dirac Point in Monolayer HfGeTe
• Hybrid Dirac Semimetal in CaAgBi Materials Family
• Enhancing Electron Coherence via Quantum Phonon Confinement in Atomically Thin Nb3SiTe6
• Topological surface superconductivity in doped Weyl loop materials
• Hourglass Fermion Surface States in Stacked Topological Insulators with Nonsymmorphic Symmetry

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