Measuring off-diagonal correlation function in stochastic series expansion quantum Monte Carlo simulation

This paper mainly introduces an algorithm for computing the off-diagonal correlation functions with directed loop update algorithm within the stochastic series expansion framework．Taking the one-dimensional Heisenberg model and the easy-plane XXZ model as examples, we calculate the spin-spin correlation function and squared staggered magnetization in the XY plane using the algorithm and validate the correction of the algorithm by comparing results with those obtained using the DMRG method．