THE PHYSICS OF FRUSTRATION IN A KAGOMÉ LATTICE ANTIFERROMAGNET

 

Joel S. Helton* and Young S. Lee (PhD Mentor)

Department of Physics, Massachusetts Institute of Technology

*Current address: NIST Center for Neutron Research

 

An important challenge in condensed matter physics is the search for quantum disordered ground states in two-dimensional systems.  The strong degree of geometric frustration in the loosely connected kagomé lattice, coupled with the enhancement of quantum fluctuations arising from S=1/2 spins, has long been acknowledged as a particularly promising in which to search for novel quantum states of matter.  The mineral herbertsmithite, ZnCu3(OH)6Cl2, is the first structurally perfect S=1/2 kagomé lattice antiferromagnet to be synthesized.  We report neutron scattering, specific heat, and magnetization measurements on this system.  Herbertsmithite shows no sign of long range Néel order or spin freezing down to temperatures of at least 50 mK, despite nearest-neighbor antiferromagnetic coupling of 17 meV.  Herbertsmithite appears to be a strong candidate to display the long sought after spin liquid ground state.