Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet
We report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material [Cu(pz)2(2−HOpy)2](PF6)2. At zero field, a transition to long-range order occurs at 1.38 K, caused by a weak intrinsic...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
American Physical Society
2023
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| _version_ | 1797109669610651648 |
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| author | Opherden, D Tepaske, MSJ Bärtl, F Weber, M Turnbull, MM Lancaster, T Blundell, SJ Baenitz, M Wosnitza, J Landee, CP Moessner, R Luitz, DJ Kühne, H |
| author_facet | Opherden, D Tepaske, MSJ Bärtl, F Weber, M Turnbull, MM Lancaster, T Blundell, SJ Baenitz, M Wosnitza, J Landee, CP Moessner, R Luitz, DJ Kühne, H |
| author_sort | Opherden, D |
| collection | OXFORD |
| description | We report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material [Cu(pz)2(2−HOpy)2](PF6)2. At zero field, a transition to long-range order occurs at 1.38 K, caused by a weak intrinsic easy-plane anisotropy and an interlayer exchange of J′/kB≈1 mK. Because of the moderate intralayer exchange coupling of J/kB=6.8 K, the application of laboratory magnetic fields induces a substantial XY anisotropy of the spin correlations. Crucially, this provides a significant BKT regime, as the tiny interlayer exchange J′ only induces 3D correlations upon close approach to the BKT transition with its exponential growth in the spin-correlation length. We employ nuclear magnetic resonance measurements to probe the spin correlations that determine the critical temperatures of the BKT transition as well as that of the onset of long-range order. Further, we perform stochastic series expansion quantum Monte Carlo simulations based on the experimentally determined model parameters. Finite-size scaling of the in-plane spin stiffness yields excellent agreement of critical temperatures between theory and experiment, providing clear evidence that the nonmonotonic magnetic phase diagram of [Cu(pz)2(2−HOpy)2](PF6)2 is determined by the field-tuned XY anisotropy and the concomitant BKT physics. |
| first_indexed | 2024-03-07T07:44:45Z |
| format | Journal article |
| id | oxford-uuid:f9e8144c-d40f-4d44-8408-40d675d1015d |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T07:44:45Z |
| publishDate | 2023 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | oxford-uuid:f9e8144c-d40f-4d44-8408-40d675d1015d2023-05-24T11:37:49ZField-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnetJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:f9e8144c-d40f-4d44-8408-40d675d1015dEnglishSymplectic ElementsAmerican Physical Society2023Opherden, DTepaske, MSJBärtl, FWeber, MTurnbull, MMLancaster, TBlundell, SJBaenitz, MWosnitza, JLandee, CPMoessner, RLuitz, DJKühne, HWe report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material [Cu(pz)2(2−HOpy)2](PF6)2. At zero field, a transition to long-range order occurs at 1.38 K, caused by a weak intrinsic easy-plane anisotropy and an interlayer exchange of J′/kB≈1 mK. Because of the moderate intralayer exchange coupling of J/kB=6.8 K, the application of laboratory magnetic fields induces a substantial XY anisotropy of the spin correlations. Crucially, this provides a significant BKT regime, as the tiny interlayer exchange J′ only induces 3D correlations upon close approach to the BKT transition with its exponential growth in the spin-correlation length. We employ nuclear magnetic resonance measurements to probe the spin correlations that determine the critical temperatures of the BKT transition as well as that of the onset of long-range order. Further, we perform stochastic series expansion quantum Monte Carlo simulations based on the experimentally determined model parameters. Finite-size scaling of the in-plane spin stiffness yields excellent agreement of critical temperatures between theory and experiment, providing clear evidence that the nonmonotonic magnetic phase diagram of [Cu(pz)2(2−HOpy)2](PF6)2 is determined by the field-tuned XY anisotropy and the concomitant BKT physics. |
| spellingShingle | Opherden, D Tepaske, MSJ Bärtl, F Weber, M Turnbull, MM Lancaster, T Blundell, SJ Baenitz, M Wosnitza, J Landee, CP Moessner, R Luitz, DJ Kühne, H Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title | Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title_full | Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title_fullStr | Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title_full_unstemmed | Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title_short | Field-tunable Berezinskii-Kosterlitz-Thouless correlations in a Heisenberg magnet |
| title_sort | field tunable berezinskii kosterlitz thouless correlations in a heisenberg magnet |
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