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Canadian Journal of Physics

Magnetic diffusion effect of Landau states

Cheng Da, Fan Hong-Yi

Published Nov 21, 2025• 0 citations
Publisher

Abstract

This study aims to explore the magnetic diffusion effect of Landau states from the perspective of quantum mechanics while the magnetic diffusion often occurs in plasmas physics. By introducing the entangled state representation, we examine how the Landau state diffuses in the presence of magnetic diffusion. We also establish the master equation of the density operator corresponding to magnetic diffusion and solve it, and we find that the Landau state evolves into a Laguerre-polynomial-weighted chaotic state.

DOI
10.1139/cjp-2024-0190

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This study aims to explore the magnetic diffusion effect of Landau states from the perspective of quantum mechanics while the magnetic diffusion often occurs in plasmas physics. By introducing the entangled state representation, we examine how the Landau state diffuses in the presence of magnetic diffusion. We also establish the master equation of the density operator corresponding to magnetic diffusion and solve it, and we find that the Landau state evolves into a Laguerre-polynomial-weighted chaotic state.
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Diffusive transport is a ubiquitous phenomenon, yet the microscopic origin of diffusion in interacting physical systems remains a challenging question, irrespective of whether quantum effects are dominant or not. In this work, we study infinite temperature spin diffusion in a classical integrable, space-time discrete version of anisotropic Landau-Lifshitz magnet in the easy-axis regime, subjected to integrability-breaking perturbations. Our numerical results based on large-scale simulations reveal i) a sharp change in the spin diffusion constant as a function of perturbation strength in the thermodynamic limit and ii) a crossover from non-Gaussian to Gaussian statistics of magnetization transfer reflected in higher order cumulants under integrability breaking. Both our observations hint to the presence of non-trivial diffusion mechanism inherent to integrable systems.
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By virtue of the properties of thermal entanglement, we succeed to obtain the solution to the representative phase diffusion master equation and give the operator sum representation of density operator. After analyzing the time evolution process of density operator at different initial state, we find out density operators keep invariable with the initial state being Fock state or thermal state. But the system always maintains coherence with phase diffusion when the initial state is coherent state.
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