Liu Yuefei, Miranda Ivan P, Johnson Lee, Bergman Anders, Delin Anna, Thonig Danny, Pereiro Manuel, Eriksson Olle, Azimi-Mousolou Vahid, Sjöqvist Erik
KTH Royal Institute of Technology, Department of Applied Physics, School of Engineering Sciences, AlbaNova University Center, SE-10691 Stockholm, Sweden.
Uppsala University, Department of Physics and Astronomy, Box 516, SE-751 20 Uppsala, Sweden.
Phys Rev Lett. 2024 Dec 31;133(26):266704. doi: 10.1103/PhysRevLett.133.266704.
The Landau-Lifshitz-Gilbert (LLG) and Landau-Lifshitz (LL) equations play an essential role for describing the dynamics of magnetization in solids. While a quantum analog of the LL dynamics has been proposed in [Phys. Rev. Lett. 110, 147201 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.147201], the corresponding quantum version of LLG remains unknown. Here, we propose such a quantum LLG equation that inherently conserves purity of the quantum state. We examine the quantum LLG dynamics of a dimer consisting of two interacting spin-1/2 particles. Our analysis reveals that, in the case of ferromagnetic coupling, the evolution of initially uncorrelated spins mirrors the classical LLG dynamics. However, in the antiferromagnetic scenario, we observe pronounced deviations from classical behavior, underscoring the unique dynamics of becoming a spinless state, which is nonlocally correlated. Moreover, when considering spins that are initially entangled, our study uncovers an unusual form of revival-type quantum correlation dynamics, which differs significantly from what is typically seen in open quantum systems.
朗道-栗弗席兹-吉尔伯特（LLG）方程和朗道-栗弗席兹（LL）方程在描述固体中磁化强度的动力学方面起着至关重要的作用。虽然在[《物理评论快报》110, 147201 (2013)PRLTAO0031 - 900710.1103/PhysRevLett.110.147201]中已经提出了LL动力学的量子类似物，但相应的量子版LLG仍然未知。在此，我们提出这样一个量子LLG方程，它本质上能保持量子态的纯度。我们研究了由两个相互作用的自旋 - 1/2粒子组成的二聚体的量子LLG动力学。我们的分析表明，在铁磁耦合的情况下，初始不相关自旋的演化反映了经典的LLG动力学。然而，在反铁磁情形下，我们观察到与经典行为有明显偏差，这突出了变成无自旋态的独特动力学，该无自旋态是非局部相关的。此外，当考虑初始纠缠的自旋时，我们的研究发现了一种不同寻常的复兴型量子关联动力学形式，它与开放量子系统中通常所见的情况有显著差异。
