Short-range correlations in the magnetic ground state of $Na_{4} Ir_{3} O_{8} $

The magnetic ground state of the candidate three-dimensional quantum spin liquid $Na_{4} Ir_{3} O_{8} $ has been studied through bulk magnetization, muon spin relaxation and neutron scattering measurements. $Na_{4} Ir_{3} O_{8} $ possesses a unique hyper-Kagome lattice of Ir moments that is potentially accompanied by a novel realization of Heisenberg-Kitaev exchange. This fact combined with the absence of previously reported magnetic ordering has led to its candidacy as a three-dimensional quantum spin liquid. Our combined experimental data show that a short-range, frozen, ground state comprised of quasi-static moments develops in this material below a characteristic temperature $T_{F} =6K$, persisting down until at least 20 mK. The expected dynamical ground state of a quantum spin liquid was not observed but rather an inhomogeneous quasi-static spin state that survives with persistent long timescale fluctuations.