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Quantum Brownian motion for magnets
- Spin precession in magnetic materials is commonly modelled with the classical phenomenological Landau-Lifshitz-Gilbert (LLG) equation. Based on a quantized three-dimensional spin + environment Hamiltonian, we here derive a spin operator equation of motion that describes precession and includes a general form of damping that consistently accounts for memory, coloured noise and quantum statistics. The LLG equation is recovered as its classical, Ohmic approximation. We further introduce resonant Lorentzian system-reservoir couplings that allow a systematic comparison of dynamics between Ohmic and non-Ohmic regimes. Finally, we simulate the full non-Markovian dynamics of a spin in the semi-classical limit. At low temperatures, our numerical results demonstrate a characteristic reduction and flattening of the steady state spin alignment with an external field, caused by the quantum statistics of the environment. The results provide a powerful framework to explore general three-dimensional dissipation in quantum thermodynamics.
Author details: | Janet AndersORCiD, Connor R. J. SaitORCiD, Simon A. R. HorsleyORCiD |
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DOI: | https://doi.org/10.1088/1367-2630/ac4ef2 |
ISSN: | 1367-2630 |
Title of parent work (English): | New journal of physics : the open-access journal for physics |
Publisher: | IOP Publ. Ltd. |
Place of publishing: | Bristol |
Publication type: | Article |
Language: | English |
Date of first publication: | 2022/03/21 |
Publication year: | 2022 |
Release date: | 2023/06/08 |
Tag: | LLG equation; coloured and quantum noise; dynamics; magnetisation; memory effects; open quantum systems; quantum thermodynamics; spin |
Volume: | 24 |
Issue: | 3 |
Article number: | 033020 |
Number of pages: | 21 |
Funding institution: | Royal Society; EPSRC Centre for Doctoral Training in Electromagnetic; Metamaterials [EP/L015331/1]; EPSRC [EP/R045577/1]; TATA [RPG-2016-186] |
Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC classification: | 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik |
Peer review: | Referiert |
Publishing method: | Open Access / Gold Open-Access |
DOAJ gelistet | |
License (German): | CC-BY - Namensnennung 4.0 International |