# A Model for Metastable Magnetism in the Hidden-Order Phase of URu2Si2

## TL;DR

This paper presents a Ginzburg-Landau model explaining the polar Kerr effect observed in URu2Si2's hidden-order phase, suggesting metastable ferromagnetism can occur without TRS breaking in the ground state.

## Contribution

It introduces a theoretical model showing how metastable ferromagnetic states can produce PKE in a TRS-preserving hidden-order phase.

## Key findings

- Metastable ferromagnetic states can cause PKE without TRS breaking.
- A strong reversed magnetic field can reset the PKE signal.
- The model explains experimental observations of PKE in URu2Si2.

## Abstract

We propose an explanation for the experiment by Schemm et al., Phys. Rev. B 91, 140506 (2015) where the polar Kerr effect (PKE), indicating time-reversal symmetry (TRS) breaking, was observed in the hidden-order (HO) phase of URu2Si2. The PKE signal on warmup was seen only if a training magnetic field was present on cool-down. Using a Ginzburg-Landau model for a complex order parameter, we show that the system can have a metastable ferromagnetic state producing the PKE, even if the HO ground state respects TRS. We predict that a strong reversed magnetic field should reset the PKE to zero.