Impurity effects in the quantum kagome system Zn Cu3 (OH)6 Cl2

Abstract

Motivated by the recent experiments on the spin half kagome compound Zn Cu3 (OH)6 Cl2, we study a phenomenological model of a frustrated quantum magnet. The model has a spin liquid ground state and is constructed so as to mimic the macroscopically large quasidegeneracies expected in the low-lying energy structure of a kagome system. We use numerical studies of finite size systems to investigate the static as well as the dynamical responses at finite temperatures. The results obtained using our simple model are compatible with a large number of recent experiments including neutron scattering data. Our study suggests that many of the anomalous features observed in experiments have a natural interpretation in terms of spin- 1 2 defects (impurities) coupled to an underlying kagome-type spin liquid. © 2008 The American Physical Society.