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Two-gap to single-gap superconducting transition on a honeycomb lattice in $C_{a1−x}Sr_{x}AlSi$


Walicka, Dorota I; Guguchia, Zurab; Lago, Jorge; Blacque, Olivier; Ma, KeYuan; Liu, Huanlong; Khasanov, Rustem; von Rohr, Fabian O (2021). Two-gap to single-gap superconducting transition on a honeycomb lattice in $C_{a1−x}Sr_{x}AlSi$. Physical review research, 3:033192.

Abstract

We report on the structural and microscopic superconducting properties of the $C_{a1−x}Sr_{x}AlSi$ solid solution. Specifically, we have realized the continuous solid solution, which for all members, other than $x=0$ (CaAlSi), crystallizes in the $AlB_{2}$-type structure. For CaAlSi, we present an improved structural model where all Al/Si layers are buckled, leading to a 6-folded structure along the crystallographic $c$ direction. We, furthermore, find indications for the structural instability in the parent compound CaAlSi to enhance the superconductivity across the solid solution. Our investigation of the magnetic penetration depths by means of muon-spin rotation experiments reveals that CaAlSi is a two-gap superconductor, that SrAlSi is a single-gap superconductor, and that there is a continuous transition from one electronic state to the other across the solid solution. Hence, we show that the $C_{a1−x}Sr_{x}AlSi$ solid solution is a highly tunable two-gap to single-gap superconducting system on a honeycomb lattice, where the superconductivity is strongly connected to a structural instability, i.e., the buckling of the Al/Si layers.

Abstract

We report on the structural and microscopic superconducting properties of the $C_{a1−x}Sr_{x}AlSi$ solid solution. Specifically, we have realized the continuous solid solution, which for all members, other than $x=0$ (CaAlSi), crystallizes in the $AlB_{2}$-type structure. For CaAlSi, we present an improved structural model where all Al/Si layers are buckled, leading to a 6-folded structure along the crystallographic $c$ direction. We, furthermore, find indications for the structural instability in the parent compound CaAlSi to enhance the superconductivity across the solid solution. Our investigation of the magnetic penetration depths by means of muon-spin rotation experiments reveals that CaAlSi is a two-gap superconductor, that SrAlSi is a single-gap superconductor, and that there is a continuous transition from one electronic state to the other across the solid solution. Hence, we show that the $C_{a1−x}Sr_{x}AlSi$ solid solution is a highly tunable two-gap to single-gap superconducting system on a honeycomb lattice, where the superconductivity is strongly connected to a structural instability, i.e., the buckling of the Al/Si layers.

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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
Scopus Subject Areas:Physical Sciences > General Physics and Astronomy
Uncontrolled Keywords:General Earth and Planetary Sciences, General Environmental Science
Language:English
Date:26 August 2021
Deposited On:13 Jan 2022 14:48
Last Modified:09 Nov 2022 15:08
Publisher:American Physical Society
ISSN:2643-1564
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1103/physrevresearch.3.033192
Project Information:
  • : FunderSNSF
  • : Grant IDPZ00P2_174015
  • : Project TitleChemistry and Physics of Nitride Based Materials
  • : FunderSNSF
  • : Grant IDPCEFP2_194183
  • : Project TitleDiscovery of Topological Superconductivity by Combining Physical and Chemical Design Principles
  • Content: Published Version
  • Language: English
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)