Green's function approach to the magnetic properties of the kagome antiferromagnet

The S=1/2 Heisenberg antiferromagnet is studied on the kagome lattice by using a Green's function method based on an appropriate decoupling of the equations of motion. Thermodynamic properties as well as spin-spin correlation functions are obtained, and characterize this system as a two-dimensional quantum spin liquid. Spin-spin correlation functions decay exponentially with distance down to low temperature, and the calculated missing entropy at T=0 is found to be 0.46 ln 2. Within the present scheme, the specific heat exhibits a single peak structure with a T-2 dependence at low temperature.