First-principles study on cubic pyrochlore iridates Y2Ir2O7 and Pr2Ir2O7

Fumiyuki Ishii; Yo Pierre Mizuta; Takehiro Kato; Taisuke Ozaki; Hongming Weng; Shigeki Onoda

doi:10.7566/JPSJ.84.073703

paper

First-principles study on cubic pyrochlore iridates Y2Ir2O7 and Pr2Ir2O7

arXiv:1505.02391 · doi:10.7566/JPSJ.84.073703

Abstract

Fully relativistic first-principles electronic structure calculations based on a noncollinear local spin density approximation (LSDA) are performed for pyrochlore iridates Y $_{2}$ Ir $_{2}$ O $_{7}$ and Pr $_{2}$ Ir $_{2}$ O $_{7}$ . The all-in, all-out antiferromagnetic (AF) order is stablized by the on-site Coulomb repulsion $U > U_{c}$ in the LSDA+ $U$ scheme, with $U_{c} \sim 1.1$ ~eV and 1.3~eV for Y $_{2}$ Ir $_{2}$ O $_{7}$ and Pr $_{2}$ Ir $_{2}$ O $_{7}$ , respectively. AF semimetals with and without Weyl points and then a topologically trivial AF insulator successively appear with further increasing $U$ . For $U = 1.3$ ~eV, Y $_{2}$ Ir $_{2}$ O $_{7}$ is a topologically trivial narrow-gap AF insulator having an ordered local magnetic moment $\sim 0.5 μ_{B}$ /Ir, while Pr $_{2}$ Ir $_{2}$ O $_{7}$ is barely a paramagnetic semimetal with electron and hole concentrations of $0.016$ /Ir, in overall agreements with experiments. With decreasing oxygen position parameter $x$ describing the trigonal compression of IrO $_{6}$ octahedra, Pr $_{2}$ Ir $_{2}$ O $_{7}$ is driven through a non-Fermi-liquid semimetal having only an isolated Fermi point of $Γ_{8}^{+}$ , showing a quadratic band touching, to a $Z_{2}$ topological insulator.

5 pages, 6 figures, with supplemental materials

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Cited by in corpus (1)

Evolution of structure, magnetism and electronic transport in doped pyrochlore iridate Y $_{2}$ Ir $_{2 - x}$ Ru $_{x}$ O $_{7}$