Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters

While either a spin or point-group adaptation is straightforward when considered independently, the standard technique for factoring isotropic spin Hamiltonians by the total spin <i>S</i> and the irreducible representation <inline-formula><math xmlns="http://www.w3.org/1998...

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Main Authors: Shadan Ghassemi Tabrizi, Thomas D. Kühne
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Magnetism
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Online Access:https://www.mdpi.com/2673-8724/5/1/8
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author Shadan Ghassemi Tabrizi
Thomas D. Kühne
author_facet Shadan Ghassemi Tabrizi
Thomas D. Kühne
author_sort Shadan Ghassemi Tabrizi
collection DOAJ
description While either a spin or point-group adaptation is straightforward when considered independently, the standard technique for factoring isotropic spin Hamiltonians by the total spin <i>S</i> and the irreducible representation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Γ</mi></semantics></math></inline-formula> of the point group is limited by the complexity of the transformations between different coupling schemes that are related in terms of their site permutations. To overcome these challenges, we apply projection operators directly to uncoupled basis states, enabling the simultaneous treatment of spin and point-group symmetry without the need for recoupling transformations. This provides a simple and efficient approach for the exact diagonalization of isotropic spin models, which we illustrate, with applications in Heisenberg spin rings and polyhedra, including systems that are computationally inaccessible with conventional coupling techniques.
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spelling doaj-art-a77eeeee1f6541f7ba02bc2a6676e1f82025-08-20T01:49:00ZengMDPI AGMagnetism2673-87242025-03-0151810.3390/magnetism5010008Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin ClustersShadan Ghassemi Tabrizi0Thomas D. Kühne1Center for Advanced Systems Understanding (CASUS), Am Untermarkt 20, 02826 Görlitz, GermanyCenter for Advanced Systems Understanding (CASUS), Am Untermarkt 20, 02826 Görlitz, GermanyWhile either a spin or point-group adaptation is straightforward when considered independently, the standard technique for factoring isotropic spin Hamiltonians by the total spin <i>S</i> and the irreducible representation <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">Γ</mi></semantics></math></inline-formula> of the point group is limited by the complexity of the transformations between different coupling schemes that are related in terms of their site permutations. To overcome these challenges, we apply projection operators directly to uncoupled basis states, enabling the simultaneous treatment of spin and point-group symmetry without the need for recoupling transformations. This provides a simple and efficient approach for the exact diagonalization of isotropic spin models, which we illustrate, with applications in Heisenberg spin rings and polyhedra, including systems that are computationally inaccessible with conventional coupling techniques.https://www.mdpi.com/2673-8724/5/1/8spin Hamiltoniansexact diagonalizationsymmetrymolecular magnetism
spellingShingle Shadan Ghassemi Tabrizi
Thomas D. Kühne
Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
Magnetism
spin Hamiltonians
exact diagonalization
symmetry
molecular magnetism
title Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
title_full Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
title_fullStr Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
title_full_unstemmed Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
title_short Simultaneous Spin and Point-Group Adaptation in Exact Diagonalization of Spin Clusters
title_sort simultaneous spin and point group adaptation in exact diagonalization of spin clusters
topic spin Hamiltonians
exact diagonalization
symmetry
molecular magnetism
url https://www.mdpi.com/2673-8724/5/1/8
work_keys_str_mv AT shadanghassemitabrizi simultaneousspinandpointgroupadaptationinexactdiagonalizationofspinclusters
AT thomasdkuhne simultaneousspinandpointgroupadaptationinexactdiagonalizationofspinclusters