A signature of hidden order in URu2Si2 : the excitation at the wavevector Q0 = (100)

TL;DR

This study identifies a specific low-energy excitation at wavevector Q0 as a signature of the hidden order phase in URu2Si2, which disappears when the material transitions to antiferromagnetic order under pressure.

Contribution

It provides direct experimental evidence linking the excitation at Q0 to the hidden order phase, clarifying its role in the phase transition of URu2Si2.

Findings

The excitation at Q0 is a signature of the hidden order state.

The excitation disappears in the antiferromagnetic phase.

The incommensurate excitation persists but shifts in energy.

Abstract

Simultaneous neutron-scattering and thermal expansion measurements on the heavy-fermion superconductor URu2Si2 under hydrostatic pressure of 0.67 GPa have been performed in order to detect the successive paramagnetic, hidden order, and large moment antiferromagnetic phases on cooling. The temperature dependence of the sharp low energy excitation at the wavevector Q_0=(100) shows that this excitation is clearly a signature of the hidden order state. In the antiferromagnetic phase, this collective mode disappears. The higher energy excitation at the incommensurate wavevector Q_1=(1.4,0,0) persists in the antiferromagnetic phase but increases in energy. The collapse of the inelastic neutron scattering at Q_0 coincides with the previous observation of the disappearance of superconductivity.