Magnetic-field-induced chiral hidden order in URu2Si2

Two of the most striking and yet unresolved manifestations of the hidden order (HO) in URu2Si2, 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 c-axis. Here we provide for the first time a unified understanding of these puzzling phenomena and the related field-temperature (B-T) phase diagram. We demonstrate that the HO phase at finite fields can be explained with a chiral dxy+idx2-y2 spin density wave, assuming that the zero field HO contains only the time-reversal symmetry preserving idx2-y2 component. We argue that the presence of the field-induced chiral HO can be reflected in a distinctive non-linear B-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.