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Title: Nexus fermions in topological symmorphic crystalline metals

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.
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
Publication Date:
Grant/Contract Number:
FG02-05ER46200; NRFNRFF2013- 03; FG02-07ER46352; AC02-05CH11231; GBMF4547
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Nature Publishing Group
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Univ. 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); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Gordon and Betty Moore Foundation
Country of Publication:
United States
36 MATERIALS SCIENCE; Electronic properties and materials; Topological insulators
OSTI Identifier: