Symmetry of the Excitations in the Hidden Order State of URu2Si2

TL;DR

This study uses polarized Raman scattering to investigate the hidden order phase in URu2Si2, revealing symmetry-specific excitations and providing constraints on theoretical models of the phase transition.

Contribution

It presents new experimental evidence of symmetry-breaking in URu2Si2's hidden order state through Raman scattering, constraining existing theories.

Findings

Detection of a 1.7 meV excitation with A2g symmetry

Evidence of translational symmetry breaking along the c axis

Correlation between Raman and neutron scattering signatures

Abstract

We have performed polarized electronic Raman scattering on URu2Si2 single crystals at low temperature down to 8 K in the hidden order state and under magnetic field up to 10 T. The hidden order state is characterized by a sharp excitation at 1.7 meV and a gap in the electronic continuum below 6.8 meV. Both Raman signatures are of pure A2g symmetry. By comparing the behavior of the Raman sharp excitation and the neutron resonance at Q0=(0,0,1), we provide new evidence, constrained by selection rules of the two probes, that the hidden order state breaks the translational symmetry along the c axis such that Gamma and Z points fold on top of each other. The observation of these distinct Raman features with a peculiar A2g symmetry as a signature of the hidden order phase places strong constraints on current theories of the hidden order in URu2Si2.