title: Evidence for a gapped spin-liquid ground state in a kagome Heisenberg antiferromagnet.
abstract: The kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite [ZnCu3(OH)6Cl2], which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χ(kagome), deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ~ 200 kelvin is the copper-copper superexchange interaction. Combined with the magnetic field dependence of χ(kagome) that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada.
authors.forename: Mingxuan
authors.initials: M
authors.lastname: Fu
authors.affiliation: Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S4M1, Canada. Canadian Institute for Advanced Research, Toronto, Ontario M5G1Z8, Canada.
authors.forename: Takashi
authors.initials: T
authors.lastname: Imai
authors.affiliation: James Franck Institute and Department of Physics, University of Chicago, Chicago, IL 60637, USA. Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Tian-Heng
authors.initials: TH
authors.lastname: Han
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Department of Applied Physics and Department of Photon Science, Stanford University and SLAC National Accelerator Laboratory, Stanford, CA 94305, USA.
authors.forename: Young S
authors.initials: YS
authors.lastname: Lee