CMT Seminar: The Physics of Frustration in a Spin-1/2 Kagomé Lattice Antiferromagnet

Monday, April 26, 2010 – 3:15pm
Reiss 261A
Joel S. Helton
NIST Center for Neutron Research, National Institute of Standards and Technology

A continuing challenge in the field of frustrated magnetism is the search for candidate materials which display quantum disordered ground states in two dimensions. In recent years, a great deal of attention has been given to the spin-1/2 nearest-neighbor Heisenberg antiferromagnet on the kagome lattice, consisting of corner sharing triangles. Given the high frustration of the lattice and the strength of quantum fluctuations arising from spin-1/2 moments, this system is a particularly promising candidate to display novel magnetic ground states, including the “resonating valence bond” (RVB) state proposed by Anderson. The mineral herbertsmithite, ZnCu3(OH)6Cl2, is among the best realizations yet achieved of the spin-1/2 kagome lattice antiferromagnet. This material remains disordered until temperatures of at least 50 mK, with no evidence of a spin gap. Neutron scattering and magnetization measurements offer insight into the low temperature physics of this material. The low energy dynamic susceptibility displays an anomalous scaling relation, suggesting that the field and energy scales of the response are determined only by the temperature. This scaling is discussed in relation to similar behavior seen in other systems influenced by disorder or by the proximity to a quantum critical point.

Host: Marcos Rigol