Shujuan Yuan

Tuning the J eff = 1 2 insulating state via electron doping and pressure in the double-layered iridate Sr 3 Ir 2 O 7

Sr3Ir2O7 exhibits a novel J(eff) = 1/2 insulating state that features a splitting between Jeff = 1/2 and 3/2 bands due to spin-orbit interaction. We report a metal-insulator transition in Sr3Ir2O7 via either dilute electron doping (La3+ for Sr2+) or application of high pressure up to 35 GPa. Our study of single-crystal Sr3Ir2O7 and (Sr1-xLax)(3)Ir2O7 reveals that application of high hydrostatic pressure P leads to a drastic reduction in the electrical resistivity by as much as six orders of magnitude at a critical pressure P-C = 13.2 GPa, manifesting a closing of the gap; but further increasing P up to 35 GPa produces no fully metallic state at low temperatures, possibly as a consequence of localization due to a narrow distribution of bonding angles theta. In contrast, slight doping of La3+ ions for Sr2+ ions in Sr3Ir2O7 readily induces a robust metallic state in the resistivity at low temperatures; the magnetic ordering temperature is significantly suppressed but remains finite for (Sr0.95La0.05)(3)Ir2O7 where the metallic state occurs. The results are discussed along with comparisons drawn with Sr2IrO4, a prototype of the J(eff) = 1/2 insulator.

Lattice-tuned magnetism of Ru 4 + ( 4 d 4 ) ions in single crystals of the layered honeycomb ruthenates Li 2 RuO 3 and Na 2 RuO 3

We synthesize and study single crystals of the layered honeycomb lattice Mott insulators Na2RuO3 and Li2RuO3 with magnetic Ru4+(4d4) ions. The newly found Na2RuO3 features a nearly ideal honeycomb lattice and orders antiferromagnetically at 30 K. Single-crystals of Li2RuO3 adopt a honeycomb lattice with either C2/m or more distorted P21/m below 300 K, depending on detailed synthesis conditions. We find that Li2RuO3 in both structures hosts a well-defined magnetic state, in contrast to the singlet ground state found in polycrystalline Li2RuO3. A phase diagram generated based on our results uncovers a new, direct correlation between the magnetic ground state and basal-plane distortions in the honeycomb ruthenates.

Evolution of Magnetism in Single-Crystal Ca2Ru1-xIrxO4 (0

\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}

\le

is a spin-orbit-coupled insulator with an antiferromagnetic (AFM) transition at

x

{T}_{N}=240\phantom{\rule{0.16em}{0ex}}\mathrm{K}

\le

. We report results of a comprehensive study of single-crystal

0.65)

\mathrm{S}{\mathrm{r}}_{2}\mathrm{I}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{T}{\mathrm{b}}_{x}{\mathrm{O}}_{4}\phantom{\rule{0.16em}{0ex}}(0\ensuremath{\le}x\ensuremath{\le}0.03)

Ground-state tuning of metal-insulator transition by compositional variations in BaI r 1 − x R u x O 3 ( 0 ≤ x ≤ 1 )

. This study found that a mere 3%

Evolution of Magnetism in Single-Crystal Honeycomb Iridates

(x=0.03)