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

摘要

We study the ground state of an S =1/2 anisotropic a ( ≡ J_(z)/J_(xy)) Heisenberg antiferromagnet with nearest ( J _(1)) and next-nearest ( J _(2)) 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 Néel 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 - J _(2) 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.