### Session P16: Heavy Fermions- Mostly URu2Si2

8:00 AM–11:00 AM, Wednesday, February 29, 2012
Room: 251

Chair: Jason Jeffries, Lawrence Livermore National Laboratory

Abstract ID: BAPS.2012.MAR.P16.12

### Abstract: P16.00012 : Emergent Rank-5 Nematic'' Order in URu2Si2

10:12 AM–10:24 AM

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#### Authors:

Hiroaki Ikeda
(Department of Physics, Kyoto University)

Michi-To Suzuki
(CCSE, Japan Atomic Energy Agency)

Ryotaro Arita
(Department of Applied Physics, University of Tokyo)

Tetsuya Takimoto
(Asia Pacific Center for Theoretical Physics, POSTECH)

In the strongly correlated $f$-electron systems, novel electronic states often appear due to the interplay between electron correlations and entangled spin and orbital degrees of freedom. A spectacular example is the so-called hidden-order'' phase in the heavy-electron metal URu$_{2}$Si$_{2}$. The phase transition is characterized by the large amount of entropy loss observed at $T_{HO}=17.5$K, however no evidence of magnetic/structural phase transition below $T_{HO}$ have been reported so far. Despite efforts over a quarter century, the order parameter has remained unidentified. We show here that the hidden order is a rank-5 multipole (dotriacontapole) state with $E^{-}$ symmetry, based on the first-principles theoretical approach. This novel electronic state provides natural explanations of the key features including anisotropic magnetic excitations, nearly degenerate antiferromagnetic state, and spontaneous fourfold symmetry breaking.