title: Field-induced freezing of a quantum spin liquid on the kagome lattice.
abstract: We report (17)O NMR measurements in the S=1/2 (Cu(2+)) kagome antiferromagnet Herbertsmithite ZnCu(3)(OH)(6)Cl(2) down to 45 mK in magnetic fields ranging from 2 to 12 T. While Herbertsmithite displays a gapless spin-liquid behavior in zero field, we uncover an instability toward a spin-solid phase at sub-Kelvin temperature induced by an applied magnetic field. The latter phase shows largely suppressed moments ≲0.1 μ(B) and gapped excitations. The H-T phase diagram suggests the existence of a quantum critical point at the small but finite magnetic field μ(0)H(c)=1.55(25) T. We discuss this finding in light of the perturbative Dzyaloshinskii-Moriya interaction which was theoretically proposed to sustain a quantum critical regime for the quantum kagome Heisenberg antiferromagnet model.
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud 11, UMR CNRS 8502, 91405 Orsay, France.
authors.forename: M
authors.initials: M
authors.lastname: Jeong
authors.forename: F
authors.initials: F
authors.lastname: Bert
authors.forename: P
authors.initials: P
authors.lastname: Mendels
authors.forename: F
authors.initials: F
authors.lastname: Duc
authors.forename: J C
authors.initials: JC
authors.lastname: Trombe
authors.forename: M A
authors.initials: MA
authors.lastname: de Vries
authors.forename: A
authors.initials: A
authors.lastname: Harrison