Monte Carlo Study of Correlations in Quantum Spin Chains at NonZero Temperature.pdf

EPJ manuscript No. (will be inserted by the editor) 8 9 9 Monte Carlo Study of Correlations in Quantum Spin Chains at 1 g Non–Zero Temperature u A 1,2 1, a 1 1 Y. J. Kim , M. Greven , U.–J. Wiese , and R. J. Birgeneau 8 1 1 2 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA ] l e Received: date / Revised version: date - r t Abstract. Antiferromagnetic Heisenberg spin chains with various spin values (S = 1/2, 1, 3/2, 2, 5/2) are s . studied numerically with the quantum Monte Carlo method. Effective spin S chains are realized by ferro- t a magnetically coupling n = 2S antiferromagnetic spin chains with S = 1/2. The temperature dependence m of the uniform susceptibility, the staggered susceptibility, and the static structure factor peak intensity - are computed down to very low temperatures, T/J ≈ 0.01. The correlation length at each temperature is d deduced from numerical measurements of the instantaneous spin–spin correlation function. At high tem- n peratures, very good agreement with exact results for the classical spin chain is obtained independent of the o value of S . For the S=2 chain which has a gap ∆, the correlation length and the uniform susceptibility in c the temperature range ∆ T J are well predicted by the semi–classical theory of Damle and Sachdev. [ 2 PACS. 75.10.Jm Quantized spin models – 75.40.Cx Static properties – 75.40.Mg Numerical simulation v studies 7 5 2 1 Introduction mody