Signatures of hidden order symmetry in torque oscillations, elastic constant anomalies and field induced moments in URu2Si2

TL;DR

This paper analyzes torque experiments in URu2Si2 to determine the hidden order symmetry, concluding it has degenerate E-type (yz,zx) symmetry based on angular oscillation patterns and discussing related elastic and field-induced effects.

Contribution

It provides evidence that the hidden order in URu2Si2 has degenerate E-type symmetry, excluding other candidate symmetries based on torque oscillation characteristics.

Findings

Twofold torque oscillations indicate E-type symmetry.

Quadrupolar and hexadecapolar symmetries are excluded as candidates.

Predictions for field-induced Bragg peaks and elastic anomalies are made.

Abstract

We discuss the conclusions on the symmetry of hidden order (HO) in URu2Si2 that may be drawn from recent torque experiments in rotating magnetic field by Okazaki et al. [1]. They are very sensitive to changes in the magnetic susceptibility induced by HO. We show that the observed twofold angular torque oscillations give evidence that hidden order has degenerate E- type (yz,zx) symmetry where both components are realised. The oscillations have the wrong characteristics or are absent for the 1D nontrivial representations like quadrupolar B1 (x^2-y^2) and B2 (xy) type HO or hexadecapolar A2(xy(x^2-y^2)) type HO. Therefore they may be excluded as candidates for hidden order. We also predict the field-angular variation of possible field-induced Bragg peaks based on underlying E-type order parameter and discuss the expected elastic constant anomalies.