Two-dimensional topological semimetal states in monolayers Cu${}_2$Ge, Fe${}_2$Ge, and Fe${}_2$Sn

Abstract

Recent experimental realizations of the topological semimetal states in several monolayer systems are very attractive because of their exotic quantum phenomena and technological applications. Based on first-principles density-functional theory calculations including spin-orbit coupling, we here explore the drastically different two-dimensional (2D) topological semimetal states in three monolayers Cu${}_2$Ge, Fe${}_2$Ge, and Fe${}_2$Sn, which are isostructural with a combination of the honeycomb Cu or Fe lattice and the triangular Ge or Sn lattice. We find that (i) the nonmagnetic (NM) Cu${}_2$Ge monolayer having a planar geometry exhibits the massive Dirac nodal lines, (ii) the ferromagentic (FM) Fe${}_2$Ge monolayer having a buckled geometry exhibits the massive Weyl points, and (iii) the FM Fe${}_2$Sn monolayer having a planar geometry and an out-of-plane magnetic easy axis exhibits the massless Weyl nodal lines. It is therefore revealed that mirror symmetry cannot protect the four-fold degenerate Dirac nodal lines in the NM Cu${}_2$Ge monolayer, but preserves the doubly degenerate Weyl nodal lines in the FM Fe${}_2$Sn monolayer. Our findings demonstrate that the interplay of crystal symmetry, magnetic easy axis, and band topology is of importance for tailoring various 2D topological states in Cu${}_2$Ge, Fe${}_2$Ge, and Fe${}_2$Sn monlayers.

References in corpus (41)

• Electronic Structure of Pyrochlore Iridates: From Topological Dirac Metal to Mott Insulator
• Weyl and Dirac Semimetals in Three Dimensional Solids
• Wannier90: A Tool for Obtaining Maximally-Localised Wannier Functions
• Discovery of a Weyl Fermion Semimetal and Topological Fermi Arcs
• WannierTools: An open-source software package for novel topological materials
• Discovery of a Three-dimensional Topological Dirac Semimetal, Na3Bi
• Topological nodal semimetals
• Colloquium: Topological Band Theory
• Giant anomalous Hall effect in a ferromagnetic Kagome-lattice semimetal
• Dirac Cone Protected by Non-Symmorphic Symmetry and 3D Dirac Line Node in ZrSiS
• Topological Node-Line Semimetal in Three Dimensional Graphene Networks
• Topological Semimetals
• Large intrinsic anomalous Hall effect in half-metallic ferromagnet Co3Sn2S2 with magnetic Weyl fermions
• Topological Phases in Two-Dimensional Materials: A Brief Review
• Topological nodal-line fermions in ZrSiSe and ZrSiTe
• Predicting the Spin-Lattice Order of Frustrated Systems from First-Principles
• Discovery of two-dimensional Dirac nodal line fermions in monolayer Cu2Si
• Discovery of Dirac Node Arcs in PtSn4
• Topological Nodal Line Semimetals in CaP3 family of materials
• Topological nodal-line semimetals in alkaline-earth stannides, germanides and silicides
• Dirac node lines in pure alkali earth metals
• Symmetry Demanded Topological Nodal-line Materials
• Two-dimensional Weyl Half Semimetal and Tunable Quantum Anomalous Hall Effect in Monolayer PtCl${}_3$
• Magnetic stress as a driving force of structural distortions: the case of CrN
• Two-Dimensional Node-Line Semimetals in a Honeycomb-Kagome Lattice
• Discovery of Weyl nodal lines in a single-layer ferromagnet
• Two-dimensional nodal-loop half metal in monolayer MnN
• Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets
• Topological nodal-line semimetals in ferromagnetic rare-earth-metal monohalides
• Prediction of Weyl semimetal, AFM topological insulator, nodal line semimetal, and Chern insulator phases in Bi2MnSe4
• Topological Weyl and Node-Line Semimetals in Ferromagnetic Vanadium-Phosphorous-Oxide $\beta$-V${}_2$OPO${}_4$ Compound
• Unconventional topological phase transition in two-dimensional systems with space-time inversion symmetry
• Two-dimensional topological nodal line semimetal in layered $X_{2}Y$ ($X$ = Ca, Sr, and Ba; $Y$ = As, Sb, and Bi)
• Strain-induced gauge and Rashba fields in ferroelectric Rashba lead chalcogenide PbX monolayers (X = S, Se, Te)
• Underlying topological Dirac nodal line mechanism of anomalously large electron-phonon coupling strength on Be (0001) surface
• Ferromagnetic Type-II Weyl Semimetal in Pyrite Chromium Dioxide
• Room-Temperature Ferromagnetic Topological Phase in CrO${}_2$: From Tripe Fermions to Weyl Fermions
• Hidden Weyl Fermions in Paramagnetic Electride Y${}_2$C
• Ferromagnetic nodal-line metal in monolayer {\em h}-InC
• Strain Controlled Magnetic and Optical Properties of Monolayer 2H-TaSe${}_2$
• Strain-induced effects in the electronic and spin properties of a monolayer of ferromagnetic GdAg2

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• Triply degenerate nodal line and tunable contracted-drumhead surface state in a tight-binding model