Phase Transition of the S=1/2 Quantum Anisotropic Heisenberg Antiferromagnet on the Triangular Lattice
We study the S=1/2 anisotropic Heisenberg antiferromagnet on finite triangular lattices with N≤24 sites : H=2JΣ_<<i, j>>(S^x_i S^x_j+S^y_i S^y_j+ΔS^z_i S^z_j) with 0≤Δ≤1. The specific heat C and the chiral-order parameter <X^2> are calculated using a quantum transfer Monte Carlo method. Remarkable differences in the size dependences of C and <X^2> are found between the cases of Δ≤0.4 and of Δ≥0.6. For Δ≤0.4, the peak height of C increases with increasing N and an extrapolation of <X^2> to the thermodynamic limit gives a finite, non-zero value at low temperatures. In contrast with these, for Δ≥0.6, the peak height does not increase and the extrapolation of <X^2> gives a smaller value even at very low temperatures indicating the absence of a long-range chiral-order. From the results, we suggest that the chiral-ordered phase transition occurs at a finite, non-zero temperature when Δ≤Δ_c with Δ_c≳0.4.
- Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy
Science reports of the Research Institutes, Tohoku University. Ser. A, Physics, chemistry and metallurgy 40 (2), 233-238, 1995-03-20