Thermodynamic evidence for broken fourfold rotational symmetry in the hidden-order phase of URu2Si2

Abstract

Despite more than a quarter century of research, the nature of the second-order phase transition in the heavy-fermion metal URu${}_2$Si${}_2$ remains enigmatic. The key question is which symmetry is being broken below this "hidden order" transition. We review the recent progress on this issue, particularly focusing on the thermodynamic evidence from very sensitive micro-cantilever magnetic torque measurements that the fourfold rotational symmetry of the underlying tetragonal crystal is broken. The angle dependence of the torque under in-plane field rotation exhibits the twofold oscillation term, which sets in just below the transition temperature. This observation restricts the symmetry of the hidden order parameter to the $E^{+}$- or $E^{-}$-type, depending on whether the time reversal symmetry is preserved or not.

7 pages, 5 figures, brief review article for Physica C Special Issue on Stripes and Electronic Liquid Crystals in Strongly Correlated Systems, updated references and added some discussion

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Cited by in corpus (7)

• Hidden Order Behaviour in URu2Si2 (A Critical Review of the Status of Hidden Order in 2014)
• Hidden order and beyond: an experimental-theoretical overview of the multifaceted behavior of URu${}_2$Si${}_2$
• Broken symmetries in URu2Si2
• Cyclotron resonance study of quasiparticle mass and scattering rate in the hidden-order and superconducting phases of URu2Si2
• Superconducting phase within the hidden-order state of the heavy-fermion material $\mathrm{UR}{\mathrm{u}}_2\mathrm{S}{\mathrm{i}}_2$
• Skyrmions in a density wave state: a mechanism for chiral superconductivity
• Phenomenological theory of the superconducting state inside the hidden-order phase of URu${}_2$Si${}_2$