Evidence for even parity unconventional superconductivity in Sr2RuO4

Aaron Chronister, Andrej Pustogow, Naoki Kikugawa, Dmitry A. Sokolov, Fabian Jerzembeck, Clifford W. Hicks, A.P. Mackenzie, Eric D. Bauer, Stuart E. Brown

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57 Citations (Scopus)
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Unambiguous identification of the superconducting order parameter symmetry in Sr2RuO4 has remained elusive for more than a quarter century. While a chiral p-wave ground state analogue to superfluid 3He-A was ruled out only very recently, other proposed triplet-pairing scenarios are still viable. Establishing the condensate magnetic susceptibility reveals a sharp distinction between even-parity (singlet) and odd-parity (triplet) pairing since the superconducting condensate is magnetically polarizable only in the latter case. Here field-dependent 17O Knight shift measurements, being sensitive to the spin polarization, are compared to previously reported specific heat measurements for the purpose of distinguishing the condensate contribution from that due to quasiparticles. We conclude that the shift results can be accounted for entirely by the expected field-induced quasiparticle response. An upper bound for the condensate magnetic response of < 10% of the normal state susceptibility is sufficient to exclude all purely odd-parity candidates. 
Original languageEnglish
Article numbere2025313118
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number25
Publication statusPublished - 22 Jun 2021


  • Unconventional superconductivity
  • Triplet pairing
  • Sr2RuO4
  • Nuclear magnetic resonance
  • Knight shift
  • Order parameter


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