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Title: Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs 3

Abstract

The existence of closed loops of degeneracies in crystals has been intimately connected with associated crystal symmetries, raising the following question: What is the minimum symmetry required for topological character, and can one find an example? Triclinic CaAs 3 , in the space group P1¯ with only a center of inversion, has been found to display, without need for tuning, a nodal loop of accidental degeneracies with topological character, centered on one face of the Brillouin zone that is otherwise fully gapped. The small loop is very flat in energy, yet is cut four times by the Fermi energy, a condition that results in an intricate repeated touching of inversion related pairs of Fermi surfaces at Weyl points. Spin-orbit coupling lifts the fourfold degeneracy along the loop, leaving trivial Kramers pairs. Here, with its single nodal loop that emerges without protection from any point group symmetry, CaAs 3 represents the primal “hydrogen atom” of nodal loop systems.

Authors:
 [1];  [1];  [2]
  1. Beijing Normal Univ. (China). Dept. of Physics and Center for Advanced Quantum Studies
  2. Univ. of California, Davis, CA (United States). Dept. of Physics
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1544395
Alternate Identifier(s):
OSTI ID: 1353141
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 118; Journal Issue: 17; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English

Citation Formats

Quan, Y., Yin, Z. P., and Pickett, W. E. Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs3. United States: N. p., 2017. Web. doi:10.1103/PhysRevLett.118.176402.
Quan, Y., Yin, Z. P., & Pickett, W. E. Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs3. United States. doi:10.1103/PhysRevLett.118.176402.
Quan, Y., Yin, Z. P., and Pickett, W. E. Tue . "Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs3". United States. doi:10.1103/PhysRevLett.118.176402. https://www.osti.gov/servlets/purl/1544395.
@article{osti_1544395,
title = {Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs3},
author = {Quan, Y. and Yin, Z. P. and Pickett, W. E.},
abstractNote = {The existence of closed loops of degeneracies in crystals has been intimately connected with associated crystal symmetries, raising the following question: What is the minimum symmetry required for topological character, and can one find an example? Triclinic CaAs3, in the space group P1¯ with only a center of inversion, has been found to display, without need for tuning, a nodal loop of accidental degeneracies with topological character, centered on one face of the Brillouin zone that is otherwise fully gapped. The small loop is very flat in energy, yet is cut four times by the Fermi energy, a condition that results in an intricate repeated touching of inversion related pairs of Fermi surfaces at Weyl points. Spin-orbit coupling lifts the fourfold degeneracy along the loop, leaving trivial Kramers pairs. Here, with its single nodal loop that emerges without protection from any point group symmetry, CaAs3 represents the primal “hydrogen atom” of nodal loop systems.},
doi = {10.1103/PhysRevLett.118.176402},
journal = {Physical Review Letters},
number = 17,
volume = 118,
place = {United States},
year = {2017},
month = {4}
}

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Works referenced in this record:

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