Multipole order and global/site symmetry in the hidden order phase of URu2Si2

TL;DR

This paper uses group theory and first-principles calculations to analyze high-rank multipole orderings in URu2Si2, aiming to identify the primary order parameter behind its mysterious hidden order phase.

Contribution

It applies Shubnikov group theory to classify multipole ordered states and elucidates how certain antiferroic multipole orders can conceal the primary order parameter.

Findings

High-symmetry charge distribution preserves the primary order.

Explicit classification of low-rank multipoles relevant to experiments.

Antiferroic magnetic multipole orderings are plausible hidden order candidates.

Abstract

On the basis of group theory and the first-principles calculations, we investigate high-rank multipole orderings in URu2Si2, which have been proposed as a genuine primary order parameter in the hidden order phase below 17.5K. We apply Shubnikov group theory to the multipole ordered states characterized by the wave vector Q = (0, 0, 1) and specify the global/site symmetry and the secondary order parameters, such as induced dipole moments and change in charge distribution. We find that such antiferroic magnetic multipole orderings have particularly advantageous to conceal the primary order parameter due to preserving high symmetry in charge distribution. Experimental observations of the inherent low-rank multipoles, which are explicitly classified in this paper, will be key pieces to understand the puzzling hidden order phase.