Iridium Orbital Crossover at the Structural Phase Transition in Ca10(Ir4As8)(Fe2-xIrxAs2)5

Kento Sugawara; Naoyuki Katayama; Yuki Sugiyama; Takafumi Higuchi; Kazutaka Kudo; Daisuke Mitsuoka; Minoru Nohara; Hiroshi Sawa

arXiv · 1402.3889

Iridium Orbital Crossover at the Structural Phase Transition in Ca10(Ir4As8)(Fe2-xIrxAs2)5

Kento Sugawara·Naoyuki Katayama·Yuki Sugiyama·Takafumi Higuchi·Kazutaka Kudo·Daisuke Mitsuoka·Minoru Nohara·Hiroshi Sawa

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Abstract

We report a structural transition found in Ca10(Ir4As8)(Fe2-xIrxAs2)5, which exhibits superconductivity at 16 K, with a layer of divalent iridium coordinated by arsenic in between Fe2As2 layers. The c-axis parameter is doubled below a structural transition temperature of approximately 100 K, while the tetragonal symmetry with space group P4/n (No.85) is unchanged at all temperatures measured. Our synchrotron x-ray diffraction study clearly shows displacements along the z-direction occur in half of the iridium sites, resulting in a complex orbital ordering pattern. Combining our theoretical calculation of the 5d orbital energies with structural data, we propose the iridium orbital crossover transition between the dxy and dz2 orbitals.

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Kento Sugawara, Naoyuki Katayama, Yuki Sugiyama, Takafumi Higuchi, Kazutaka Kudo, Daisuke Mitsuoka, Minoru Nohara, Hiroshi Sawa. 2014-02-17. Iridium Orbital Crossover at the Structural Phase Transition in Ca10(Ir4As8)(Fe2-xIrxAs2)5. https://arxiv.org/abs/1402.3889

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