Phase Diagram of an S = 1/2 J 1 - J 2 Anisotropic Heisenberg Antiferromagnet on a Triangular Lattice

We study the ground state of an S=1/2 anisotropic a (≡Jz/Jxy) Heisenberg antiferromagnet with nearest (J1) and next-nearest (J2) neighbor exchange interactions on a triangular lattice using the exact diagonalization method. We obtain the energy, squared sublattice magnetizations, and their Binder ratios on finite lattices with N≤36 sites. We estimate the threshold J(t) 2 (a) between the three-sublattice Neel state and the spin liquid (SL) state, and J(s) 2 (a)  between the stripe state and the SL state. The SL state exists over a wide range in the α-J2 plane. For α>1 , the xy component of the magnetization is destroyed by quantum fluctuations, and the classical distorted 120° structure is replaced by the collinear state.