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Superconducting order parameter of the nodal-line semimetal NaAlSi


Muechler, Lukas; Guguchia, Zurab; Orain, Jean-Christophe; Nuss, Jürgen; Schoop, Leslie M; Thomale, Ronny; von Rohr, Fabian O (2019). Superconducting order parameter of the nodal-line semimetal NaAlSi. APL Materials, 7(12):121103.

Abstract

Nodal-line semimetals are topologically nontrivial states of matter featuring band crossings along a closed curve, i.e., nodal-line, in momen-tum space. Through a detailed analysis of the electronic structure, we show, for the first time, that the normal state of the superconductorNaAlSi, with a critical temperature ofTc≈7 K, is a nodal-line semimetal, where the complex nodal-line structure is protected by nonsym-morphic mirror crystal symmetries. We further report on muon spin rotation experiments revealing that the superconductivity in NaAlSi istruly of bulk nature, featuring a fully gapped Fermi-surface. The temperature-dependent magnetic penetration depth can be well described bya two-gap model consisting of twos-wave symmetric gaps withΔ1= 0.6(2) meV andΔ2= 1.39(1) meV. The zero-field muon experiment indi-cates that time-reversal symmetry is preserved in the superconducting state. Our observations suggest that, notwithstanding its topologicallynontrivial band structure, NaAlSi may be suitably interpreted as a conventional London superconductor, while more exotic superconductinggap symmetries cannot be excluded. The intertwining of topological electronic states and superconductivity renders NaAlSi a prototypicalplatform to search for unprecedented topological quantum phases.

Abstract

Nodal-line semimetals are topologically nontrivial states of matter featuring band crossings along a closed curve, i.e., nodal-line, in momen-tum space. Through a detailed analysis of the electronic structure, we show, for the first time, that the normal state of the superconductorNaAlSi, with a critical temperature ofTc≈7 K, is a nodal-line semimetal, where the complex nodal-line structure is protected by nonsym-morphic mirror crystal symmetries. We further report on muon spin rotation experiments revealing that the superconductivity in NaAlSi istruly of bulk nature, featuring a fully gapped Fermi-surface. The temperature-dependent magnetic penetration depth can be well described bya two-gap model consisting of twos-wave symmetric gaps withΔ1= 0.6(2) meV andΔ2= 1.39(1) meV. The zero-field muon experiment indi-cates that time-reversal symmetry is preserved in the superconducting state. Our observations suggest that, notwithstanding its topologicallynontrivial band structure, NaAlSi may be suitably interpreted as a conventional London superconductor, while more exotic superconductinggap symmetries cannot be excluded. The intertwining of topological electronic states and superconductivity renders NaAlSi a prototypicalplatform to search for unprecedented topological quantum phases.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
07 Faculty of Science > Physics Institute
Dewey Decimal Classification:540 Chemistry
Language:English
Date:1 December 2019
Deposited On:14 Feb 2020 09:23
Last Modified:16 Feb 2020 07:08
Publisher:American Institute of Physics
ISSN:2166-532X
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1063/1.5124242
Project Information:
  • : FunderSNSF
  • : Grant IDPZ00P2_174015
  • : Project TitleChemistry and Physics of Nitride Based Materials
  • : FunderDFG
  • : Grant ID258499086–SFB 11
  • : Project Title
  • : Funderct.qmat
  • : Grant ID39085490–EXC 214
  • : Project Title
  • : FunderNSF
  • : Grant IDDMR-142054
  • : Project Title

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