Magnetic-field-induced chiral hidden order in URu₂Si₂

Abstract

Two of the most striking and yet unresolved manifestations of the hidden order (HO) in are associated, on one hand, with the double-step metamagnetic transitions and, on the other, with the giant anomalous Nernst signal. Both are observed when a magnetic field is applied along the -axis. Here, we provide for the first time a unified understanding of these puzzling phenomena and the related field–temperature () phase diagram. We demonstrate that the HO phase at finite fields can be explained with a chiral spin density wave, assuming that the zero-field HO contains only the time-reversal symmetry preserving component. We argue that the presence of the field-induced chiral HO can be reflected in a distinctive non-linear dependence of the Kerr angle, when a Kerr experiment is conducted for finite fields. This fingerprint can be conclusive for the possible emergence of chirality in the HO.

Keywords:

• URu₂Si₂
• hidden order
• chirality
• itinerant metamagnetism
• anomalous Nernst effect
• polar Kerr effect

Acknowledgements

We are indebted to J. Mydosh, P.M. Oppeneer, Y. Matsuda, K. Behnia and A. Kapitulnik for illuminating discussions. This work was partially funded by by NTU Athens. A. A. wishes to thank the organizers of the Workshop on HO, Superconductivity and Magnetism in , Lorentz Center, Leiden for their hospitality.