High-pressure versus isoelectronic doping effect on the honeycomb iridate Na2IrO3

Article

关键词: TOTAL-ENERGY CALCULATIONS;    DIFFRACTION;    TRANSITION;    GRAPHITE;    STATE;   

DOI  :  10.1103/PhysRevB.96.195137

来源: SCIE

【 摘 要 】

We study the effect of isoelectronic doping and external pressure in tuning the ground state of the honeycomb iridate Na2IrO3 by combining optical spectroscopy with synchrotron x-ray diffraction measurements on single crystals. The obtained optical conductivity of Na2IrO3 is discussed in terms of a Mott-insulating picture versus the formation of quasimolecular orbitals and in terms of Kitaev interactions. With increasing Li content x, (Na1-xLix)(2)IrO3 moves deeper into theMott-insulating regime, and there are indications that up to a doping level of 24% the compound comes closer to the Kitaev limit. The optical conductivity spectrum of single-crystalline alpha-Li2IrO3 does not follow the trends observed for the series up to x = 0.24. There are strong indications that alpha-Li2IrO3 is not as close to the Kitaev limit as Na2IrO3 and lies closer to the quasimolecular orbital picture instead. Except for the pressure-induced hardening of the phonon modes, the optical properties of Na2IrO3 seem to be robust against external pressure. Possible explanations of the unexpected evolution of the optical conductivity with isolectronic doping and the drastic change between x = 0.24 and x = 1 are given by comparing the pressure-induced changes of lattice parameters and the optical conductivity with the corresponding changes induced by doping.

【 授权许可】

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