Interlayer magnetic-frustration–driven quantum spin disorder in the honeycomb compound In3Cu2VO9

In this paper we present the electronic and magnetic properties of the honeycomb compound In3Cu2VO9. We find that the band dispersions display Dirac cone features in the nonmagnetic phase, as observed in graphene. The parent phase is a charge transfer insulator with an energy gap of about 1.5 eV. Singly occupied electrons of copper ions contribute an spin, while vanadium ions show nonmagnetism. The planar nearest-neighbor, next-nearest-neighbor and interplane superexchange couplings of Cu spins are , and , suggesting a low-dimensional antiferromagnet rather than a spin liquid. We propose that the magnetic frustration along the c-axis leads to a quantum spin disorder in In3Cu2VO9, in accordance with recent experiments.