Complex Landau Ginzburg Theory of the Hidden Order in URu_2Si_2

TL;DR

This paper develops a complex Landau Ginzburg theoretical framework to unify the hidden order and antiferromagnetic phases in URu_2Si_2, explaining experimental phenomena and phase diagram features.

Contribution

It introduces a unified complex order parameter to describe both phases and predicts experimental signatures like the phase diagram topology and low-energy modes.

Findings

Unified the hidden order and antiferromagnetic phases with a complex order parameter.

Predicted the topology of the phase diagram in magnetic field and pressure.

Identified a pseudo-Goldstone mode near the commensurate wavevector.

Abstract

We develop a Landau Ginzburg theory of the hidden order phase and the local moment antiferromagnetic phase of URu_2Si_2. We unify the two broken symmetries in a common complex order parameter and derive many experimentally relevant consequences such as the topology of the phase diagram in magnetic field and pressure. The theory accounts for the appearance of a moment under application of stress and the thermal expansion anomaly across the phase transitions. It identifies the low energy mode which is seen in the hidden order phase near the conmensurate wavector (0,0, 1) as the pseudo-Goldstone mode of the approximate U(1) symmetry.