Scale-free antiferromagnetic fluctuations in the s = 1/2 kagome antiferromagnet herbertsmithite.
Neutron spectroscopy and diffuse neutron scattering on herbertsmithite [ZnCu(3)(OH)(6)Cl(2)], a near-ideal realization of the s=1/2 kagome antiferromagnet, reveal the hallmark property of a quantum spin liquid: instantaneous short-ranged antiferromagnetic correlations in the absence of a time-averaged ordered moment. These dynamic antiferromagnetic correlations are weakly dependent of neutron-energy transfer and temperature, and persist up to 25 meV and 120 K. At low energy transfers a shift of the magnetic scattering to low Q is observed with increasing temperature, providing evidence of gapless spinons. It is argued that these observations provide important evidence in favor of resonating-valence-bond theories of (doped) Mott insulators.
de Vries
M A
MA
School of Physics & Astronomy, University of St-Andrews, the North Haugh, St Andrews, KY16 9SS, United Kingdom. m.a.devries@physics.org
Stewart
J R
JR
Deen
P P
PP
Piatek
J O
JO
Nilsen
G J
GJ
Rønnow
H M
HM
Harrison
A
A