The unconventional superconductivity of skutterudite PrOs 4Sb 12: Time-reversal symmetry breaking and adjacent field-induced quadrupole ordering

Yuji Aoki, Takashi Tayama, Toshiro Sakakibara, Keitaro Kuwahara, Kazuaki Iwasa, Masahumi Kohgi, Wataru Higemoto, Douglas E. MacLaughlin, Hitoshi Sugawara, Hideyuki Sato

Research output: Contribution to journalReview articlepeer-review

59 Citations (Scopus)


This review presents a summary and evaluation of the experimental properties of unconventional superconductivity in PrOs 4Sb 12. After a brief introduction of filled skutterudites, we argue that the normal-state properties of PrOs 4Sb 12 are quite different from ordinary heavy-fermion superconductors, in the sense that the 4f-electrons seem to be well localized even at low temperatures where the superconductivity appears. This is reflected in the existence of a field-induced antiferro-quadrupole ordering of Pr 4f-electrons. It is shown that the 4f collective excitations can be described as quadrupolar excitons. Their strong temperature dependence in close correlation with the superconductivity suggests a conjecture that the superconducting mechanism may involve quadrupolar-exciton- mediated pairing of some kind. Although the structure of the superconducting order parameter is far from conclusive, outstanding experimental observations reported to date reveal the uniqueness of the unconventional superconducting state. Special focus is given to time-reversal symmetry breaking in the superconducting state. The article concludes with a discussion of some key issues and desirable future work.

Original languageEnglish
Article number051006
Journaljournal of the physical society of japan
Issue number5
Publication statusPublished - 2007 May


  • Filled skutterudite
  • Heavy fermion superconductor
  • PrOs Sb
  • Quadrupolar exciton
  • Quadrupole ordering
  • Time-reversal symmetry breaking

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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