Symmetry of the hidden order in URu 2Si 2 from nuclear magnetic resonance studies

Shigeru Takagi, Shu Ishihara, Makoto Yokoyama, Hiroshi Amitsuka

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35 Citations (Scopus)


The hidden order (HO) in URu 2Si 2 has been investigated by both 29Si and 99Ru NMR on a single crystal. Tiny, but finite additional broadening of the spectrum in the HO phase in both 29Si and 99Ru NMR with external magnetic field applied along the crystallographic [100] or [110] direction, and its persistence as H ext → 0 in 29Si NMR clearly indicate the existence of internal hyperfine field, and the breaking of the time-reversal symmetry in the HO phase can therefore be concluded. We discuss which symmetry of the D 4h symmetry group of the URu 2Si 2 crystal structure is compatible with the observed dependence on the crystal-axis direction of the existence or nonexistence of the internal hyperfine field. Then, by imposing a strong constraint that the wave-vector of the HO is also Q 0 = [0;0;1], the wave-vector of the pressure-induced antiferromagnetism, we show that the two-dimensional representation E - remains as the only possible candidate for the HO symmetry. Since dipoles are obviously excluded from the major HO parameter, we conclude the E - multipole (octupole or triakontadipole) to be the HO parameter. We further discuss that the E -multipole, but with no associated dipoles, seems to be a key feature of the HO in URu 2Si 2.

Original languageEnglish
Article number114710
Journaljournal of the physical society of japan
Issue number11
Publication statusPublished - 2012 Nov


  • Hidden order
  • Multipole
  • NMR
  • Octupole
  • Time-reversal symmetry
  • Triakontadipole
  • URu Si

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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