Evidence for a Gapped Spin-Liquid Ground State in a Kagome Heisenberg Antiferromagnet

Understand

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 great debate.
• We conducted 17-O single crystal NMR measurements of the S=1/2 kagome lattice in herbertsmithite ZnCu$_3$(OH)$_6$Cl$_2$, which is known to exhibit a spinon continuum in the spin excitation spectrum.
• We demonstrate that the intrinsic local spin susceptibility $\chi_{kagome}$ deduced from the 17-O NMR frequency shift asymptotes to zero below temperature T ~ 0.03 J, where J ~ 200 K is the Cu-Cu super-exchange interaction.