101Ru NQR and hidden order in URu2Si2

Satoru Saitoh, Shigeru Takagi, Makoto Yokoyama, Hiroshi Amitsuka

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15 Citations (Scopus)


The still unclarified hidden order phase below T0 = 17.5 K in the heavy-electron system URu2Si2 has been studied by 101Ru NQR on a single crystal under Hext = 0 and ambient P. Considering an invariant form of the quadrupole coupling between a 101Ru nucleus and U 5f electrons, which is compatible with the symmetry of the U-Ru bonds, it is shown that U 5f quadrupoles can be probed by 101Ru NQR and that the singlet ground-state models for the (5f) 2 configuration of U can naturally explain the observed large T-dependence of the NQR frequency 101ν2Q(T) above T0. 101ν2Q(T) shows a slight but significant increase below TQ ≅ 13.5 K. Combining with general considerations on the effects on 101Ru NQR of a possible symmetry-breaking electric field gradient (EFG) or hyperfine field due to hidden order, we discuss that the increase can be interpreted as arising from symmetry-breaking EFG components of Vyz and/or Vzx due to quadrupole order. In this interpretation the onset of the quadrupole order is retarded by about 4 K below T0, which is discussed in connection with related measurements.

Original languageEnglish
Pages (from-to)2209-2213
Number of pages5
Journaljournal of the physical society of japan
Issue number8
Publication statusPublished - 2005 Aug


  • Heavy electron
  • NQR
  • Quadrupole order
  • U compounds
  • URuSi

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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