A Dichotomy of the Spin Liquid and the Correlated Impurities in Herbertsmithite

It is debatable whether RVB spin liquids exist in kagome systems.~ Enthusiasm in spin-1/2 kagome antiferromagnets gained extra momentum from the observation of a spinon continuum in ZnCu3(OD)6Cl2 (herbertsmithite).~ In low-energy limit, where insightful many-body theories exist, impurities complicate experimental interpretations. ~Two important progresses were made in the past year.~ Single-crystalline 17O NMR experiment provided evidence for pristine kagome layers and a spin gap. ~Below the spinon continuum's energies, neutron scattering measurements revealed 3 dimensional spin correlations, which likely originate from the impurities.~ I will present the intrinsic-extrinsic dichotomy in ZnCu3(OD)6Cl2 as well as my thoughts on future directions.