@article{639a6cb69d994b149983babb9caa6c1a,
title = "Dirac lines and loop at the Fermi level in the time-reversal symmetry breaking superconductor LaNiGa2",
abstract = "Unconventional superconductors have Cooper pairs with lower symmetries than in conventional superconductors. In most unconventional superconductors, the additional symmetry breaking occurs in relation to typical ingredients such as strongly correlated Fermi liquid phases, magnetic fluctuations, or strong spin-orbit coupling in noncentrosymmetric structures. In this article, we show that the time-reversal symmetry breaking in the superconductor LaNiGa2 is enabled by its previously unknown topological electronic band structure, with Dirac lines and a Dirac loop at the Fermi level. Two symmetry related Dirac points even remain degenerate under spin-orbit coupling. These unique topological features enable an unconventional superconducting gap in which time-reversal symmetry can be broken in the absence of other typical ingredients. Our findings provide a route to identify a new type of unconventional superconductors based on nonsymmorphic symmetries and will enable future discoveries of topological crystalline superconductors.",
author = "Badger, {Jackson R.} and Yundi Quan and Staab, {Matthew C.} and Shuntaro Sumita and Antonio Rossi and Devlin, {Kasey P.} and Kelly Neubauer and Shulman, {Daniel S.} and Fettinger, {James C.} and Peter Klavins and Kauzlarich, {Susan M.} and Dai Aoki and Vishik, {Inna M.} and Pickett, {Warren E.} and Valentin Taufour",
note = "Funding Information: We thank Rahim Ullah, Li Si, Jianxin Zhu, Junren Shi, Shingo Yonezawa, Makariy Tanatar, Ruslan Prozorov, Christopher Perez, Donhui Lu, and Makoto Hashimoto for helpful discussions. The synthesis and characterizations were supported by the UC Laboratory Fees Research Program (LFR-20-653926). V.T. also acknowledges funding from GIMRT (19F0502). The ARPES work in this manuscript was supported by AFOSR Grant No. FA9550-18-1-0156. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The work of S. S. is supported by JST CREST Grant No. JPMJCR19T2. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1548562. W.E.P and Y.Q. acknowledge support from U.S. National Science Foundation Grant DMR 1607139. Y.Q. also thank Stony Brook Research Computing and Cyberinfrastructure, and the Institute for Advanced Computational Science at Stony Brook University for access to the innovative high-performance Ookami computing system, which was made possible by National Science Foundation grant #1927880. S.M.K. and K.P.D. acknowledge support from U.S. National Science Foundation Grant DMR-2001156. K.N. and D.S.S. were supported by the NSF-REU programs PHY-1560482 and PHY-1852581. Publisher Copyright: {\textcopyright} 2022, The Author(s).",
year = "2022",
month = dec,
doi = "10.1038/s42005-021-00771-5",
language = "English",
volume = "5",
journal = "Communications Physics",
issn = "2399-3650",
publisher = "Springer Nature",
number = "1",
}