Spin-orbit interaction in Sr2IrO4 leads to the realization of the Jeff=1/2 state and also induces an insulating behavior. Using large-shift Raman spectroscopy, we found two high-energy excitations of the d-shell multiplet at 690 and 680 meV with A1g and B1g symmetry, respectively. As temperature decreases, the A1g and B1g peaks narrow, and the A1g peak shifts to higher energy while the energy of the B1g peak remains the same. When 25% of Ir is substituted with Rh the A1g peak softens by 10% but the B1g peak does not. We show that both pseudospin-flip and non-pseudo-spin-flip d-d electronic transitions are Raman active, but only the latter are observed. Our experiments and analysis place significant new constraints on the possible electronic structure of Sr2IrO4.
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Experimental work at the University of Colorado was supported by the NSF under Grant No. DMR-1410111. Theoretical work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-FG02-10ER46686 (Y.-P.H. and M.H.), and by Simons Foundation Grant No. 305008 (M.H. sabbatical support). G.C. acknowledges NSF support via Grant No. DMR-1265162.
Yang, Jhih-An; Huang, Yi-Ping; Hermele, Michael; Qi, Tongfei; Cao, Gang; and Reznik, Dmitry, "High-Energy Electronic Excitations in Sr2IrO4 Observed by Raman Scattering" (2015). Physics and Astronomy Faculty Publications. 288.