## The BKT transition and its dynamics in a spin fluid

2023
Journal article
Published
##### Published in
The Journal of Chemical Physics ; 158 (2023), 4. - 044902. - American Institute of Physics (AIP). - ISSN 0021-9606. - eISSN 1089-7690
##### Abstract
We study the effect of particle mobility on phase transitions in a spin fluid in two dimensions. The presence of a phase transition of the BKT universality class is shown in an off-lattice model of particles with purely repulsive interaction employing computer simulations. A critical spin wave region 0 < T < TBKT is found with a nonuniversal exponent η(T) that follows the shape suggested by BKT theory, including a critical value consistent with ηBKT = 1/4. One can observe a transition from power-law decay to exponential decay in the static correlation functions at the transition temperature TBKT, which is supported by finite-size scaling analysis. A critical temperature TBKT = 0.17(1) is suggested. Investigations into the dynamic aspects of the phase transition are carried out. The short-time behavior of the incoherent spin autocorrelation function agrees with the Nelson–Fisher prediction, whereas the long-time behavior differs from the finite-size scaling known for the static XY model. Analysis of coherent spin wave dynamics shows that the spin wave peak is a propagating mode that can be reasonably well fitted by hydrodynamic theory. The mobility of the particles strongly enhances damping of the spin waves, but the model still lies within the dynamic universality class of the standard XY model.
530 Physics
##### Keywords
Statistical Physics, Phase Transitions, Topological Phase Transitions
##### Cite This
ISO 690BISSINGER, Thomas, Matthias FUCHS, 2023. The BKT transition and its dynamics in a spin fluid. In: The Journal of Chemical Physics. American Institute of Physics (AIP). 158(4), 044902. ISSN 0021-9606. eISSN 1089-7690. Available under: doi: 10.1063/5.0129663
BibTex
@article{Bissinger2023trans-59890,
year={2023},
doi={10.1063/5.0129663},
title={The BKT transition and its dynamics in a spin fluid},
number={4},
volume={158},
issn={0021-9606},
journal={The Journal of Chemical Physics},
author={Bissinger, Thomas and Fuchs, Matthias},
note={DFG, German Research Foundation) – SFB 1432 – Project-ID 425217212, No. C07 Article Number: 044902}
}

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<dcterms:abstract xml:lang="eng">We study the effect of particle mobility on phase transitions in a spin fluid in two dimensions. The presence of a phase transition of the BKT universality class is shown in an off-lattice model of particles with purely repulsive interaction employing computer simulations. A critical spin wave region 0 &lt; T &lt; T&lt;sub&gt;BKT&lt;/sub&gt; is found with a nonuniversal exponent η(T) that follows the shape suggested by BKT theory, including a critical value consistent with η&lt;sub&gt;BKT&lt;/sub&gt; = 1/4. One can observe a transition from power-law decay to exponential decay in the static correlation functions at the transition temperature T&lt;sub&gt;BKT&lt;/sub&gt;, which is supported by finite-size scaling analysis. A critical temperature T&lt;sub&gt;BKT&lt;/sub&gt; = 0.17(1) is suggested. Investigations into the dynamic aspects of the phase transition are carried out. The short-time behavior of the incoherent spin autocorrelation function agrees with the Nelson–Fisher prediction, whereas the long-time behavior differs from the finite-size scaling known for the static XY model. Analysis of coherent spin wave dynamics shows that the spin wave peak is a propagating mode that can be reasonably well fitted by hydrodynamic theory. The mobility of the particles strongly enhances damping of the spin waves, but the model still lies within the dynamic universality class of the standard XY model.</dcterms:abstract>
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##### Comment on publication
DFG, German Research Foundation) – SFB 1432 – Project-ID 425217212, No. C07
Yes
Yes