Center for Correlated Electron Systems

Seminar

Time-reversal symmetry breaking hidden order in Sr2(Ir,Rh)O4

November 14, 2017l Hit 596
Date : July 28, 2017 14:00 ~ 15:00
Speaker : Dr. Jaehong Jeong(Laboratoire Léon Brillouin - CEA, France)
Location : Bldg. 19, Rm. 210

In the 5d layered perovskite material, Sr2IrO4, spin orbit coupling and strong electron correlations combine to give rise to a spin-orbit coupled Mott insulator with a pseudo-spin J=1/2 antiferromagnetic (AFM) state [1,2]. Owing to its close structural [3,4], electronic [5,6] and magnetic [3,4] similarities with the 3d layered perovskite material, La2CuO4, which evolves from a spin S=1/2 AFM Mott insulator to a high temperature superconductor upon doping, doped Sr2IrO4 has become a promising material to discover new states of matter, including unconventional superconductivity. Recently, optical second-harmonic generation (SHG) measurements in Sr2(Ir,Rh)O4 have highlighted an odd-parity hidden order, developing prior to its AFM state. This state possesses the same symmetries of a loop-current (LC) order [7], theoretically proposed to account for the pseudo-gap physics of superconducting cuprates [8,9]. The existence of such a magneto-electric state has gained support from the detection in several cuprate families of its magnetic fingerprint by polarized neutron diffraction [10,11]. Using the same technique for Sr2(Ir,Rh)O4, we have observed at the temperature of the hidden odd-parity order the appearance of a magnetic order which breaks time-reversal symmetry, while preserving lattice translation invariance [12]. Among the magnetic point groups inferred from the SHG data [7], only the co-planar LC order [8,9] produces a magnetic pattern consistent with our polarized neutron data. Our results suggest that exotic magnetic orders with the same symmetry properties as a LC phase exist in both iridates and cuprates.

 

Host: Prof. Je-Geun Park