Optical Spectroscopy and Imaging of Correlated Spin Orbit Phases
Technical Report,15 Mar 2013,14 Mar 2016
California Institute of Technology Pasadena United States
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Over the course of this ARO award we constructed three ultrafast laser based probes nonlinear optical rotational anisotropy, nonlinear optical microscopy and time-resolved optical reflectivity to search for novel electronic phases in correlated electron materials. Using these techniques, we completed five major scientific projects. 1 We discovered previously unresolved oxygen sub-lattice distortions in layered perovskite iridates, which explain the anomalous magneto-elastic coupling and basal plane ferromagnetism observed in Sr2IrO4 and Sr3Ir2O7 respectively. 2 We discovered a previously hidden odd-parity magnetic order in the pseudogap region of hole-doped Sr2IrO4, which is consistent with the long-sought orbital loop-current phase that has been conjectured to underlie the pseudogap region of the cuprate high-Tc superconductors. 3 We discovered a similar odd-parity magnetic order in the pseudogap region of hole-doped YBa2Cu3O7 that appears to terminate at a quantum critical point inside the superconducting dome. 4 We discovered an ultrafast photo-induced insulator-to-metal phase transition in Ca2RuO4 that, unlike the phase transition in thermal equilibrium, is not accompanied by any structural distortion. 5 We revealed the weak Mott insulating character of Sr3Ir2O7 and discovered the emergence of an unconventional density wave instability upon electron-doping that is reminiscent of the charge ordering recently reported in under-doped cuprates.