Time-reversal symmetry breaking hidden order in Sr$_2$(Ir,Rh)O$_4$

Jaehong Jeong (1) , Yvan Sidis (1) , Alex Louat (2) , Véronique Brouet (2) , Philippe Bourges (1)

1 LLB - UMR 12 - Laboratoire Léon Brillouin
2 LPS - Laboratoire de Physique des Solides

Layered 5d transition iridium oxides, Sr$_2$(Ir,Rh)O$_4$ , are described as unconventional Mott insulators with strong spin-orbit coupling. The undoped compound, Sr$_2$IrO$_4$ , is a nearly ideal two-dimensional pseudospin-1/2 Heisenberg antiferromagnet, similarly to the insulating parent compound of high-temperature superconducting copper oxides. Using polarized neutron diffraction, we here report a hidden magnetic order in pure and doped Sr$_2$(Ir,Rh)O$_4$ , distinct from the usual antiferromagnetic pseudospin ordering. We find that time-reversal symmetry is broken while the lattice translation invariance is preserved in the hidden order phase. The onset temperature matches that of the odd-parity hidden order recently highlighted using optical second-harmonic generation experiments. The novel magnetic order and broken symmetries can be explained by the loop-current model, previously predicted for the copper oxide superconductors.

Domains: Physics [physics]

Jaehong Jeong, Yvan Sidis, Alex Louat, Véronique Brouet, Philippe Bourges. Time-reversal symmetry breaking hidden order in Sr$_2$(Ir,Rh)O$_4$. Nature Communications, 2017, 8, pp.15119. ⟨10.1038/ncomms15119⟩. ⟨cea-02141019⟩