Abstract
We report NMR measurements in the kagome antiferromagnet Herbertsmithite 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 and gapped excitations. The phase diagram suggests the existence of a quantum critical point at the small but finite magnetic field . 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.
- Received 26 July 2011
DOI:https://doi.org/10.1103/PhysRevLett.107.237201
© 2011 American Physical Society