Emergence of novel magnetic quasiparticles and spin liquid physics in iridates

The strong spin-orbit coupling and moderate electronic correlations in iridates open fascinating new routes to realizing novel magnetic states. A prime example of this is Ba₄Ir₃O₁₀, which has been shown to host a spin liquid ground state, despite its apparently unfrustrated quasi-2D lattice of IrO₆ trimers. Here we solve this mystery using resonant inelastic x-ray scattering (RIXS) to measure the magnetic excitation spectrum, finding that it is dominated by spinons. We interpret our result using density matrix renormalization group (DMRG) model Hamiltonian calculations and density function theory calculations of hopping. These show how spins within the trimer are effectively decoupled from the lattice via the cancelation of competing interactions to yield quasi 1D physics.