Unconventional Thermal and Magnetic-Field-Driven Changes of a Bipartite Entanglement of a Mixed Spin-(1/2,<i>S</i>) Heisenberg Dimer with an Uniaxial Single-Ion Anisotropy
The concept of negativity is adapted in order to explore the quantum and thermal entanglement of the mixed spin-(1/2,<i>S</i>) Heisenberg dimers in presence of an external magnetic field. The mutual interplay between the spin size <i>S</i>, XXZ exchange and uniaxial single-io...
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| Autores principales: | , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/c190e19c4832404caf88b7524965249f |
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| Sumario: | The concept of negativity is adapted in order to explore the quantum and thermal entanglement of the mixed spin-(1/2,<i>S</i>) Heisenberg dimers in presence of an external magnetic field. The mutual interplay between the spin size <i>S</i>, XXZ exchange and uniaxial single-ion anisotropy is thoroughly examined with a goal to tune the degree and thermal stability of the pairwise entanglement. It turns out that the antiferromagnetic spin-(1/2,<i>S</i>) Heisenberg dimers exhibit higher degree of entanglement and higher threshold temperature in comparison with their ferromagnetic counterparts when assuming the same set of model parameters. The increasing spin magnitude <i>S</i> accompanied with an easy-plane uniaxial single-ion anisotropy can enhance not only the thermal stability but simultaneously the degree of entanglement. It is additionally shown that the further enhancement of a bipartite entanglement can be achieved in the mixed spin-(1/2,<i>S</i>) Heisenberg dimers, involving half-odd-integer spins <i>S</i>. Under this condition the thermal negativity saturates at low-enough temperatures in its maximal value regardless of the magnitude of half-odd-integer spin <i>S</i>. The magnetic field induces consecutive discontinuous phase transitions in the mixed spin-(1/2,<i>S</i>) Heisenberg dimers with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>S</mi><mspace width="-0.166667em"></mspace><mo>></mo><mspace width="-0.166667em"></mspace><mn>1</mn></mrow></semantics></math></inline-formula>, which are manifested in a surprising oscillating magnetic-field dependence of the negativity observed at low enough temperature. |
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