Analogy between the `hidden order’ and the orbital antiferromagnetism in URu2Si2

In URu₂Si₂ two types of staggered phases involving long range ordering of the uranium-5f electrons compete at low temperature when a critical parameter x is tuned, where x can be chemical substituent concentration, pressure or magnetic field. When cooled at below the critical value x, the non-magnetic `hidden order’ (HO) phase with broken local chiral symmetry emerges, whereas above x<sub>c</sub>, unconventional antiferromagnetic (AF) phase with broken local time-reversal symmetry appears. The two phases show strikingly similar electronic properties. `Janus faces’ nature of the HO and AF phases has been theorized before, but the experimental signatures of the interplay between them are still lacking. Here, we use polarized Raman scattering to study the dynamical fluctuations between the two competing ground states as a function of x. Albeit the distinct discrete symmetries are broken above and below x_c, we detect a resonance continuously evolving with parameter x, providing evidence for a unified order parameter across the URu₂Si₂ phase diagram.