Broken symmetries in URu2Si2

Abstract

To resolve the nature of the hidden order below 17.5\,K in the heavy fermion compound URu${}_2$Si${}_2$, identifying which symmetries are broken below the hidden order transition is one of the most important steps. Several recent experiments on the electronic structure have shown that the Fermi surface in the hidden order phase is quite close to the result of band-structure calculations within the framework of itinerant electron picture assuming the antiferromagnetism. This provides strong evidence for the band folding along the c-axis with the ordering vector of $(001)$, corresponding to broken translational symmetry. In addition to this, there is growing evidence for fourfold rotational symmetry breaking in the hidden-order phase from measurements of the in-plane magnetic anisotropy and the effective mass anisotropy in the electronic structure, as well as the orthorhombic lattice distortion. This broken fourfold symmetry gives a stringent constraint that the symmetry of the hidden order parameter should belong to the degenerate $E$-type irreducible representation. We also discuss a possibility that time reversal symmetry is also broken, which further narrows down the order parameter that characterizes the hidden order.

12 pages, 5 figures. Brief review article for the focused issue on Hidden Order for Philosophical Magazine

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Cited by in corpus (6)

• Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2
• Symmetry protected line nodes in non-symmorphic magnetic space groups: Applications to UCoGe and UPd${}_2$Al${}_3$
• Theory of surface Andreev bound states and tunneling spectroscopy in three-dimensional chiral superconductors
• Ultrafast nematic-orbital excitation in FeSe
• Thermodynamic approach to electric quadrupole moments
• Hidden order symmetry and superconductivity in URu2Si2 investigated by quasiparticle interference