Emergent Rank-5 'Nematic' Order in URu2Si2

TL;DR

This paper reveals that the hidden-order phase in URu2Si2 is characterized by a rank-5 multipole 'nematic' order with E^- symmetry, explaining various experimental observations through a first-principles theoretical approach.

Contribution

It identifies the hidden-order parameter as a rank-5 multipole order with nematic symmetry, providing a comprehensive theoretical explanation for the phase's features.

Findings

Identifies the hidden order as a rank-5 multipole with nematic symmetry.

Explains anisotropic magnetic excitations and symmetry breaking.

Accounts for nearly degenerate antiferromagnetic state.

Abstract

Novel electronic states resulting from entangled spin and orbital degrees of freedom are hallmarks of strongly correlated f-electron systems. A spectacular example is the so-called 'hidden-order' phase transition in the heavy-electron metal URu2Si2, which is characterized by the huge amount of entropy lost at T_{HO}=17.5K. However, no evidence of magnetic/structural phase transition has been found below T_{HO} so far. The origin of the hidden-order phase transition has been a long-standing mystery in condensed matter physics. Here, based on a first-principles theoretical approach, we examine the complete set of multipole correlations allowed in this material. The results uncover that the hidden-order parameter is a rank-5 multipole (dotriacontapole) order with 'nematic' E^- symmetry, which exhibits staggered pseudospin moments along the [110] direction. This naturally provides comprehensive explanations of all key features in the hidden-order phase including anisotropic magnetic excitations, nearly degenerate antiferromagnetic-ordered state, and spontaneous rotational-symmetry breaking.