摘要
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.