Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals
Abstract
In quantum field theory, we learn that fermions come in three varieties: Majorana, Weyl, and Dirac. Here we show that in solid state systems this classification is incomplete and find several additional types of crystal symmetry-protected free fermionic excitations . We exhaustively classify linear and quadratic 3-, 6- and 8- band crossings stabilized by space group symmetries in solid state systems with spin-orbit coupling and time-reversal symmetry. Several distinct types of fermions arise, differentiated by their degeneracies at and along high symmetry points, lines, and surfaces. Some notable consequences of these fermions are the presence of Fermi arcs in non-Weyl systems and the existence of Dirac lines. Ab-initio calculations identify a number of materials that realize these exotic fermions close to the Fermi level.
Keywords
Cite
@article{arxiv.1603.03093,
title = {Beyond Dirac and Weyl fermions: Unconventional quasiparticles in conventional crystals},
author = {Barry Bradlyn and Jennifer Cano and Zhijun Wang and M. G. Vergniory and C. Felser and R. J. Cava and B. Andrei Bernevig},
journal= {arXiv preprint arXiv:1603.03093},
year = {2016}
}
Comments
v1: main text 9pgs. 29pg supplementary material. Submitted on 2/18/2016 v2: 2 new authors and 19 new materials added. Discussion of 4-band spin-3/2 fermions added, with emphasis on overlap with other materials of interest. Discussion of Zeeman splitting and other experimental implications added. v3: Accepted version. Minor typos fixed, title changed (formerly "New fermions"). Now 10+41pgs