Ground states of a two - dimensional frustrated quantum antiferromagent Cs 2 CuC 14

The properties of a frustrated quantum antiferromagnet are interesting topics in condensed matter theory. Among the quantum antiferromagnets, Cs2CuC14 gains attention as one of the candidates for materials with ground state spin liquid phase. The recent experimental results show that there exist several ground state phases in the presence of magnetic field which cannot be explained with classical Hamiltonian. In the thesis, I numerically studied the ground state of Cs2 CuC14 using a modified classical Hamiltonian, and I compared the result with previous experiments and classical analysis. The resulted magnetic phase diagram contains two phases, cone and ferromagnetic phase, which are separated by second order transition and a first order transition line for intermediate longitudinal field which ends up with a critical point. Thesis Supervisor: Professor Xiao-Gang Wen Title: Department of Physics