Green’s function approach to the magnetic properties of the kagomé antiferromagnet

The $S=1/2\mathrm{}$ Heisenberg antiferromagnet is studied on the kagomé 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 $T=0\mathrm{}$ 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.