Abstract
Topologically protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology. While in some metals these quasiparticles are direct analogues of elementary fermionic particles of the relativistic quantum field theory, other metals can have symmetries that give rise to quasiparticles, fundamentally different from those known in high-energy physics. Here we report on a new type of topological quasiparticles -- triple point fermions -- realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries. We find two topologically different types of triple point fermions, both distinct from any other topological quasiparticles reported to date. We provide examples of existing materials that host triple point fermions of both types, and discuss a variety of physical phenomena associated with these quasiparticles, such as the occurrence of topological surface Fermi arcs, transport anomalies and topological Lifshitz transitions.
Highlights
Materials with nontrivial band structure topology, apart from possible technological applications, provide a test ground for the concepts of fundamental physics theories in relatively cheap condensed matter experiments
Protected fermionic quasiparticles appear in metals, where band degeneracies occur at the Fermi level, dictated by the band structure topology
We report on a new type of topological quasiparticles—triple point fermions—realized in metals with symmorphic crystal structure, which host crossings of three bands in the vicinity of the Fermi level protected by point group symmetries
Summary
Materials with nontrivial band structure topology, apart from possible technological applications, provide a test ground for the concepts of fundamental physics theories in relatively cheap condensed matter experiments. The recent discovery of Weyl semimetals in the TaAs materials class [1,2,3,4,5] provided materials, where two bands cross linearly at isolated points in momentum space, called Weyl points (WPs) [6] These WPs occur close to the Fermi level, and the low-energy excitations in these metals are described by the Weyl equation of the relativistic quantum field theory, allowing for experimental studies of Weyl fermions, examples of which in highenergy physics are still lacking. We use the example of the predicted family of compounds to discuss the topological surface states arising in TPTMs and the response of these materials to external magnetic fields
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
