Quantum Spin Dynamics by Path Integral Centroid Molecular Dynamics Method

Abstract

Quantum spin dynamics in mesoscopic magnets has received much attention over the recent years, both experimentally and theoretically. Especially, molecular magnets such as the ferric wheel or Mn12 have emerged as promising candidates for the experimental observation of macroscopic quantum phenomena such as the tunneling of the magnetization. We investigated tunneling rates of model manganese systems by means of the nonlinear σ model. 1) The path integral centroid molecular dynamics (CMD) 2),3) method has been shown to be capable of simulating the real time quantum dynamics of complicated many-body systems, even for reasonably long time, albeit approximately. So far, this method has been applied to calculating dynamical properties in systems consisting of both Fermi and Bose particles. 4) In this study, we demonstrate that the centroid-based path integral method is feasible to investigate real time quantum spin dynamics at low temperature. We introduce a centroid corresponding to a spin variable as an average spin coordinate of a closed isomorphic necklace of each spin space, so-called spin centroid. We calculated magnetization of a system with S = 1.