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arXiv · 2107.14620

Effect of an uniaxial single-ion anisotropy on the quantum and thermal entanglement of a mixed spin-(1/2,$S$) Heisenberg dimer

Hana Vargová·Jozef Strečka·Natália Tomašovičová
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Abstract

Exact analytical diagonalization is used to study the bipartite entanglement of the antiferromagnetic mixed spin-(1/2,$S$) Heisenberg dimer (MSHD) with the help of negativity. Under the assumption of uniaxial single-ion anisotropy affecting higher spin-$S$ ($S\!>\!1/2$) entities only, the ground-state degeneracy $2S$ is partially lifted and the ground state is two-fold degenerate with the total magnetization per dimer $\pm(S\!-\!1/2)$. It is shown that the largest quantum entanglement is reached for the antiferromagnetic ground state of MSHD with arbitrary half-odd-integer spins $S$, regardless of the exchange and single-ion anisotropies. Contrary to this, the degree of a quantum entanglement in MSHD with an integer spin $S$ for the easy-plane single-ion anisotropy, exhibits an increasing tendency with an obvious spin-$S$ driven crossing point. It is shown that the increasing spin magnitude is a crucial driving mechanism for an enhancement of a threshold temperature above which the thermal entanglement vanishes. The easy-plane single-ion anisotropy together with an enlargement of the spin-$S$ magnitude is other significant driving mechanism for an enhancement of the thermal entanglement in MSHD.

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Hana Vargová, Jozef Strečka, Natália Tomašovičová. 2021-07-30. Effect of an uniaxial single-ion anisotropy on the quantum and thermal entanglement of a mixed spin-(1/2,$S$) Heisenberg dimer. https://doi.org/10.1016/j.jmmm.2021.168799

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