Physical review. B, Condensed matter
Spin-correlation function of theS=1antiferromagnetic Heisenberg chain atT=0
Minoru Takahashi
Abstract
The correlation function \ensuremath{\rho}(l)=〈${S}_{i}^{z}$${S}_{i+l}^{z}$〉 is calculated for the spin-1 Heisenberg antiferromagnetic chain (H=J${\ensuremath{\Sigma}}_{i}$${\mathrm{scrS}}_{i}$${\mathrm{scrS}}_{i+1}$, ${\mathrm{scrS}}_{N+1}$\ensuremath{\equiv}${\mathrm{scrS}}_{1}$) at the ground state. Using the Monte Carlo method of Hirsch, Sugar, Scalopino, and Blankenbecler we find that \ensuremath{\rho}(l) decays exponentially in contrast to the S=half case where \ensuremath{\rho}(l) decays algebraically. This fact coincides with Haldane's prediction and recent numerical calculations. We calculate the upper bound of elementary excitation from the structure factor using a variational method which resembles the Feynman theory for elementary excitation of liquid $^{4}\mathrm{He}$.