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Title: Nexus fermions in topological symmorphic crystalline metals

Journal Article · · Scientific Reports
ORCiD logo [1];  [2]; ORCiD logo [3];  [2]; ORCiD logo [1]; ORCiD logo [2];  [4];  [2];  [2]; ORCiD logo [2];  [5];  [6]; ORCiD logo [7]; ORCiD logo [8];  [1]; ORCiD logo [2]
  1. National Univ. of Singapore (Singapore). Centre for Advanced 2D Materials and Graphene Research Centre and Dept. of Physics
  2. Princeton Univ., NJ (United States). Dept. of Physics and Lab. for Topological Quantum Matter and Spectroscopy
  3. National Sun Yat-sen Univ., Kaohsiung (Taiwan). Dept. of Physics
  4. Beijing Inst. of Technology, Beijing (China). School of Physics; Singapore Univ. of Technology and Design (Singapore). Research Lab. for Quantum Materials
  5. National Tsing Hua Univ., Hsinchu (Taiwan). Dept. of Physics
  6. National Tsing Hua Univ., Hsinchu (Taiwan). Dept. of Physics; Academia Sinica, Taipei (Taiwan). Inst. of Physics
  7. Singapore Univ. of Technology and Design (Singapore). Research Lab. for Quantum Materials
  8. Princeton Univ., NJ (United States). Princeton Center for Theoretical Science; Univ. of Zurich (Switzerland). Dept. of Physics

Topological metals and semimetals (TMs) have recently drawn significant interest. These materials give rise to condensed matter realizations of many important concepts in high-energy physics, leading to wide-ranging protected properties in transport and spectroscopic experiments. It has been well-established that the known TMs can be classified by the dimensionality of the topologically protected band degeneracies. While Weyl and Dirac semimetals feature zero-dimensional points, the band crossing of nodal-line semimetals forms a one-dimensional closed loop. In this paper, we identify a TM that goes beyond the above paradigms. It shows an exotic configuration of degeneracies without a well-defined dimensionality. Specifically, it consists of 0D nexus with triple-degeneracy that interconnects 1D lines with double-degeneracy. We show that, because of the novel form of band crossing, the new TM cannot be described by the established results that characterize the topology of the Dirac and Weyl nodes. Moreover, triply-degenerate nodes realize emergent fermionic quasiparticles not present in relativistic quantum field theory. We present materials candidates. Thus, our results open the door for realizing new topological phenomena and fermions including transport anomalies and spectroscopic responses in metallic crystals with nontrivial topology beyond the Weyl/Dirac paradigm.

Research Organization:
Princeton Univ., NJ (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); National University of Singapore (Singapore); Singapore National Science Foundation; National Science Council (NSC) (Taiwan); National Center for High-performance Computing (NCHC) (Taiwan); National Center for Theoretical Sciences (NCTS) (Taiwan); National Energy Research Scientific Computing Center (NERSC); Gordon and Betty Moore Foundation
Grant/Contract Number:
FG02-05ER46200; NRFNRFF2013- 03; FG02-07ER46352; AC02-05CH11231; GBMF4547
OSTI ID:
1423565
Journal Information:
Scientific Reports, Vol. 7, Issue 1; ISSN 2045-2322
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 110 works
Citation information provided by
Web of Science

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Cited By (57)

Quadratic contact point semimetal: Theory and material realization journal September 2018
SU(3) fermions in a three-band graphene-like model journal September 2019
Topological dual double node-line semimetals NaAlSi(Ge) and their potential as cathode material for sodium ion batteries journal January 2019
Nexus networks in carbon honeycombs journal April 2018
Robust doubly charged nodal lines and nodal surfaces in centrosymmetric systems text January 2017
Design triple points, nexus points and related topological phases by stacking monolayers text January 2019
Design triple points, nexus points, and related topological phases by stacking monolayers journal August 2019
Unconventional quantum Hall effects in two-dimensional massive spin-1 fermion systems journal October 2017
Electron-phonon coupling, superconductivity and nontrivial band topology in NbN polytypes text January 2018
Dirac and nodal line magnons in three-dimensional antiferromagnets text January 2017
Unconventional Chiral Fermions and Large Topological Fermi Arcs in RhSi journal November 2017
The study of magnetic topological semimetals by first principles calculations text January 2019
Triply degenerate nodal points and topological phase transitions in NaCu 3 Te 2 journal December 2017
Topological Triply Degenerate Points Induced by Spin-Tensor-Momentum Couplings text January 2017
The study of magnetic topological semimetals by first principles calculations journal October 2019
Transport Properties of Topological Semimetal Tungsten Carbide in the 2D Limit journal February 2019
Ferromagnetic Weyl fermions in CrO 2 journal May 2018
Single-crystal investigation of the proposed type-II Weyl semimetal CeAlGe journal December 2018
Hybrid Nodal Loop Metal: Unconventional Magnetoresponse and Material Realization text January 2018
Systematic analysis for triple points in all magnetic symmorphic systems and symmetry-allowed coexistence of Dirac points and triple points journal December 2018
Dirac and Nodal Line Magnons in Three-Dimensional Antiferromagnets journal December 2017
Centrosymmetric Li 2 NaN: a superior topological electronic material with critical-type triply degenerate nodal points journal January 2019
Nodal-chain network, intersecting nodal rings and triple points coexisting in nonsymmorphic Ba3Si4 text January 2018
Magnetic and noncentrosymmetric Weyl fermion semimetals in the R AlGe family of compounds ( R = rare earth ) journal January 2018
Hybrid nodal loop metal: Unconventional magnetoresponse and material realization journal March 2018
Coexistence of four-band nodal rings and triply degenerate nodal points in centrosymmetric metal diborides journal June 2017
Quaternary Heusler alloy: An ideal platform to realize triple point fermions journal January 2019
Quadratic and cubic nodal lines stabilized by crystalline symmetry journal March 2019
Intermetallic Ca 3 Pb: a topological zero-dimensional electride material journal January 2018
Unconventional quantum Hall effects in two-dimensional massive spin-1 fermion systems text January 2017
Electrodynamics of tilted Dirac/Weyl materials: A unique platform for unusual surface plasmon polaritons text January 2019
Topological carbon allotropes: knotted molecules, carbon-nano-chain, chainmails, and Hopfene journal May 2020
Quadratic contact point semimetal: Theory and material realization text January 2018
Transport across junctions of pseudospin-one fermions journal August 2019
Quantum transport in topological semimetals under magnetic fields (II) journal April 2019
Generalized triple-component fermions: Lattice model, Fermi arcs, and anomalous transport journal December 2019
Topological Hopf and Chain Link Semimetal States and Their Application to Co 2 Mn G a journal October 2017
Robust doubly charged nodal lines and nodal surfaces in centrosymmetric systems journal October 2017
From Nodal Chain Semimetal to Weyl Semimetal in HfC journal July 2017
Topological Triply Degenerate Points Induced by Spin-Tensor-Momentum Couplings journal June 2018
Coexistent three-component and two-component Weyl phonons in TiS, ZrSe, and HfTe journal February 2018
Quadratic and Cubic Nodal Lines Stabilized by Crystalline Symmetry text January 2018
Electron-phonon coupling, superconductivity, and nontrivial band topology in NbN polytypes journal March 2019
Topology of triple-point metals journal July 2019
Prediction of threefold fermions in a nearly ideal Dirac semimetal BaAgAs journal July 2019
Coexistence of Weyl and Type‐II Triply Degenerate Fermions in a Ternary Topological Semimetal YPtP journal May 2019
Prediction of Ideal Topological Semimetals with Triply Degenerate Points in the NaCu 3 Te 2 Family journal December 2017
Nodal-chain network, intersecting nodal rings and triple points coexisting in nonsymmorphic Ba 3 Si 4 journal January 2018
Photoemission Spectroscopic Evidence for the Dirac Nodal Line in the Monoclinic Semimetal SrAs 3 journal February 2020
Topological Dirac nodal-net fermions in AlB 2 -type TiB 2 and ZrB 2 journal January 2018
Electrodynamics of tilted Dirac and Weyl materials: A unique platform for unusual surface plasmon polaritons journal November 2019
Hourglass Fermion in Two-Dimensional Material journal September 2019
Evidence from transport measurements for YR h 6 G e 4 being a triply degenerate nodal semimetal journal January 2020
Coexistence of four-band nodal rings and triply-degenerate nodal points in centrosymmetric metal diborides text January 2017
Transport across junctions of pseudospin-one fermions text January 2019
Multiple triple-point fermions in Heusler compounds journal August 2018
From Nodal Chain Semimetal To Weyl Semimetal in HfC text January 2017

Figures / Tables (7)

Figure 1(p. 3)figure Figure 1
b,c) We enclose the Weyl node by a sphere in k space. We notice that the sphere satisfies following two crucial conditions: (1) The sphere is a 2D closed manifold; (2) Bands 1 and 2 are separated by a band gap at all k points on the sphere. These two facts guarantee that one can calculate the Chern number of the filled valence bands on this sphere. Because the Wey! nodes are Berry curvature monopoles, it has been shown the Chern number ( C) of the sphere equals the chiral charge (χ) of the enclosed Weyl node, which serves as the topological invariant of the Weyl node. ( d,e) A Dirac node arises from the crossing between two doubly degenerate bands ( 1, 2 and 3, 4). We can also enclose the Dirac node by a sphere in k space. The sphere will also satisfy the same two conditions. Because a Dirac node can be viewed as two degenerate Weyl nodes of opposite chirality, it can be shown that the chiral charge of a Dirac node is always zero, i.e., χ = 0. (g-i) The new band crossing here arises from the crossing between a singly degenerate band and a doubly degenerate band. However, if we try to enclose the triply degenerate node with a sphere, we see that it is not possible to have a fully gapped band structure on the sphere. Specifically, between bands 1 and 2, the band gap vanishes at the left-pole of the sphere. Similarly, between bands 2 and 3, the band gap is zero at the right-pole of the sphere. For this reason, it is not possible to define and calculate the Chern number on the sphere as done in the Dirac/Weyl cases. (f) A trivial case where the band crossing is a simple composition of a OD Weyl node plus a 1 D nodal line." data-ostiid="1423565">
Figure 2(p. 5)figure Figure 2
Figure 3(p. 6)figure Figure 3
Figure 4(p. 7)figure Figure 4
Table 1(p. 8)table Table 1
Figure 5(p. 9)figure Figure 5
Figure 6(p. 10)figure Figure 6

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