Large trigonal-field effect on spin-orbit coupled states in a pyrochlore iridate

Uematsu, Daisuke*; Sagayama, Hajime*; Arima, Takahisa*; Ishikawa, Jun*; Nakatsuji, Satoru*; Takagi, Hidenori*; Yoshida, Masahiro*; Mizuki, Junichiro; Ishii, Kenji

The half-filled topmost valence band of Ir in several iridates such as SrIrO, IrO, and CaIrO has been proposed to originate mainly from the spin-orbit coupled states. In pyrochlore iridates IrO (: rare earth), some exotic electronic states are theoretically proposed by assuming states. However, the octahedral coordination around Ir is trigonally distorted, which may affect the energy level scheme of Ir states. Here, we report spectra of resonant elastic and inelastic X-ray scattering in EuIrO at the Ir edges. A large suppression of the magnetic scattering signal at the Ir edge supports the picture rather than the one. The inelastic scattering spectrum indicates that the magnitude of the trigonal field on the Ir states is evaluated to be comparable to the spin-orbit interaction. The energy diagram of the state is proposed based on the simple cluster model.