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Superconducting gap anisotropy and topological singularities due to lattice translational symmetry and their thermodynamic signatures


Zinkl, Bastian; Fischer, Mark H; Sigrist, Manfred (2019). Superconducting gap anisotropy and topological singularities due to lattice translational symmetry and their thermodynamic signatures. Physical review. B, 100:014519.

Abstract

Symmetry arguments based on the point group of a system and thermodynamic measurements are often combined to identify the order parameter in unconventional superconductors. However, lattice translations, which can induce additional momenta with vanishing order parameter in the Brillouin zone, are neglected, especially in gap functions otherwise expected to be constant, such as in chiral superconductors. After a general analysis of the symmetry conditions for vanishing gap functions, we study the case of chiral p- and chiral f-wave pairing on a square lattice, a situation relevant for Sr2RuO4. Specifically, we calculate the impurity-induced density of states, specific heat, superfluid density, and thermal conductivity employing a self-consistent T-matrix calculation and compare our results to the case of a nodal (d-wave) order parameter. While there is a clear distinction between a fully gapped chiral state and a nodal state, the strongly anisotropic case is almost indistinguishable from the nodal case. Our findings illustrate the difficulty of interpreting thermodynamic measurements. In particular, we find that the available measurements are consistent with a chiral (f-wave) order parameter. Our results help to reconcile the thermodynamic measurements with the overall picture of chiral spin-triplet superconductivity in Sr2RuO4.

Abstract

Symmetry arguments based on the point group of a system and thermodynamic measurements are often combined to identify the order parameter in unconventional superconductors. However, lattice translations, which can induce additional momenta with vanishing order parameter in the Brillouin zone, are neglected, especially in gap functions otherwise expected to be constant, such as in chiral superconductors. After a general analysis of the symmetry conditions for vanishing gap functions, we study the case of chiral p- and chiral f-wave pairing on a square lattice, a situation relevant for Sr2RuO4. Specifically, we calculate the impurity-induced density of states, specific heat, superfluid density, and thermal conductivity employing a self-consistent T-matrix calculation and compare our results to the case of a nodal (d-wave) order parameter. While there is a clear distinction between a fully gapped chiral state and a nodal state, the strongly anisotropic case is almost indistinguishable from the nodal case. Our findings illustrate the difficulty of interpreting thermodynamic measurements. In particular, we find that the available measurements are consistent with a chiral (f-wave) order parameter. Our results help to reconcile the thermodynamic measurements with the overall picture of chiral spin-triplet superconductivity in Sr2RuO4.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Electronic, Optical and Magnetic Materials
Physical Sciences > Condensed Matter Physics
Language:English
Date:29 July 2019
Deposited On:09 Jan 2020 11:43
Last Modified:29 Jul 2020 12:28
Publisher:American Physical Society
ISSN:2469-9950
OA Status:Green
Publisher DOI:https://doi.org/10.1103/physrevb.100.014519
Project Information:
  • : FunderSNSF
  • : Grant ID200020_184739
  • : Project TitleSupraleitung und Magnetismus in starkkorrelierten Elektronensystemen

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