Fully relativistic first-principles electronic structure calculations basedon a noncollinear local spin density approximation (LSDA) are performed forpyrochlore iridates Y$_2$Ir$_2$O$_7$ and Pr$_2$Ir$_2$O$_7$. The all-in, all-outantiferromagnetic (AF) order is stablized by the on-site Coulomb repulsion$U>U_c$ in the LSDA+$U$ scheme, with $U_c\sim1.1$~eV and 1.3~eV forY$_2$Ir$_2$O$_7$ and Pr$_2$Ir$_2$O$_7$, respectively. AF semimetals with andwithout Weyl points and then a topologically trivial AF insulator successivelyappear with further increasing $U$. For $U=1.3$~eV, Y$_2$Ir$_2$O$_7$ is atopologically trivial narrow-gap AF insulator having an ordered local magneticmoment $\sim0.5\mu_B$/Ir, while Pr$_2$Ir$_2$O$_7$ is barely a paramagneticsemimetal with electron and hole concentrations of $0.016$/Ir, in overallagreements with experiments. With decreasing oxygen position parameter $x$describing the trigonal compression of IrO$_6$ octahedra, Pr$_2$Ir$_2$O$_7$ isdriven through a non-Fermi-liquid semimetal having only an isolated Fermi pointof $\Gamma_8^+$, showing a quadratic band touching, to a $Z_2$ topologicalinsulator.
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机译：对吡咯氯铱酸盐Y $ _2 $ Ir $ _2 $ O $ _7 $和Pr $ _2 $ Ir $ _2 $ O $ _7 $进行了基于相对共线局部自旋密度近似（LSDA）的相对论第一性原理的电子结构计算。 LSDA + $ U $方案中的现场库仑排斥$ U> U_c $稳定了全进全出铁磁（AF）订单，其中$ U_c \ sim1.1 $〜eV和1.3〜eV forY $ _2 $ Ir $ _2 $ O $ _7 $和Pr $ _2 $ Ir $ _2 $ O $ _7 $。具有Weyl点和不具有Weyl点的AF半金属，然后出现拓扑琐碎的AF绝缘体，随着$ U $的进一步增加。对于$ U = 1.3 $〜eV，Y $ _2 $ Ir $ _2 $ O $ _7 $是拓扑学上较琐碎的窄间隙AF绝缘子，其有序局部磁矩$ \ sim0.5 \ mu_B $ / Ir，而Pr $ _2 $与实验总体一致，Ir $ _2 $ O $ _7 $几乎不是一种电子和空穴浓度为$ 0.016 $ / Ir的顺磁性半金属。随着氧气位置参数$ x $的下降，描述了IrO $ _6 $八面体的三角压缩，Pr $ _2 $ Ir $ _2 $ O $ _7 $通过非费米液体半金属来驱动，该非费米液体半金属仅具有孤立的费米点$ \ Gamma_8 ^。 + $，表示二次带接触到$ Z_2 $拓扑绝缘子。
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