Quantum Spin Liquid in a depleted triangular lattice Iridate K${}_x$Ir${}_y$O${}_2$

Abstract

We report discovery of a new iridate family K${}_x$Ir${}_y$O${}_2$ with depleted triangular lattice planes made up of edge sharing IrO${}_6$ octahedra separated by K planes. Such a material interpolates between the triangular and honeycomb lattices and is a new playground for Kitaev physics. The materials are Mott insulators with $y=1-x/4$. Physical property measurements for the $x\approx 0.85$ material are reported. Using magnetic susceptibility $\chi$ versus temperature $T$ measurements we find $S_{eff}=1/2$ moments interacting strongly with a Weiss temperature $\theta \approx -180$~K and no magnetic order or spin freezing down to $T=1.8$~K\@. Heat capacity shows a broad maximum around $30$~K which is insensitive to magnetic fields and a $T$-linear low temperature behaviour with $\gamma \sim 10$~mJ/mol~K${}^2$. These results are consistent with a gapless QSL state in K${}_{0.85}$Ir${}_{0.79}$O${}_2$.

5 pages, 3 figures