Honeycomb lattice iridate on the verge of Mott-collapse

Abstract

A new honeycomb lattice iridate (La,Na)IrO3 (≈LaNaIr2O6) is successfully synthesized from the spin-orbit coupled Mott insulator Na2IrO3 by replacing the interlayer Na+ ions with La3+ ions. (La,Na)IrO3 shows a finite Sommerfeld term in heat capacity and a −lnT dependence of resistivity, indicating a realization of a metallic state driven by a Mott collapse. Furthermore, crystal structure analysis reveals the formation of Ir zig-zag chains with metal-metal bonding, increasing kinetic energy resulting in the Mott collapse. This observation would be due to a Mott collapse induced in a Jeff = 1/2 spin-orbit coupling Mott insulator with an Ir honeycomb lattice by topochemical control of the ionic configuration.