Anisotropy and multiband superconductivity in Sr2RuO4 determined by small-angle neutron scattering studies of the vortex lattice

S. J. Kuhn, W. Morgenlander, E. R. Louden, C. Rastovski, W. J. Gannon, H. Takatsu, D. C. Peets, Y. Maeno, C. D. Dewhurst, J. Gavilano, M. R. Eskildsen

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Despite numerous studies the exact nature of the order parameter in superconducting Sr2RuO4 remains unresolved. We have extended previous small-angle neutron scattering studies of the vortex lattice in this material to a wider field range, higher temperatures, and with the field applied close to both the (100) and (110) basal plane directions. Measurements at high field were made possible by the use of both spin polarization and analysis to improve the signal-to-noise ratio. Rotating the field towards the basal plane causes a distortion of the square vortex lattice observed for H(001) and also a symmetry change to a distorted triangular symmetry for fields close to (100).The vortex lattice distortion allows us to determine the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane, yielding a value of ∼60 at low temperature and low to intermediate fields. This greatly exceeds the upper critical field anisotropy of ∼20 at low temperature, reminiscent of Pauli limiting. Indirect evidence for Pauli paramagnetic effects on the unpaired quasiparticles in the vortex cores are observed, but a direct detection lies below the measurement sensitivity. The superconducting anisotropy is found to be independent of temperature but increases for fields 1 T, indicating multiband superconductvity in Sr2RuO4. Finally, the temperature dependence of the scattered intensity provides further support for gap nodes or deep minima in the superconducting gap.

Original languageEnglish
Article number174507
JournalPhysical Review B
Volume96
Issue number17
DOIs
StatePublished - Nov 14 2017

Bibliographical note

Funding Information:
We acknowledge experimental assistance by D. Honecker and J. Saroni as well as useful discussions with M. Ichioka, V. G. Kogan, K. Krycka, and K. Machida. Funding was provided by the US Department of Energy, Office of Basic Energy Sciences, under Award No. DE-SC0005051 (neutron scattering), and by the Japan Society for the Promotion of Science KAKENHI No. JP15H05852 and No. JP15K21717 (crystal growth and characterization). Part of this work is based on experiments performed at the Swiss spallation neutron source SINQ, Paul Scherrer Institute, Villigen, Switzerland.

Publisher Copyright:
© 2017 American Physical Society.

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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