Thermal entanglement in the mixed three spin XXZ Heisenberg Model on a triangular cell

We numerically investigate thermal entanglement of the spins (1/2,1) and (1/2,1/2) in the three-mixed (1/2,1,1/2) anisotropic Heisenberg XXZ spin system on a simple triangular cell under an inhomogeneous magnetic field. We show that the external magnetic field induces strong plateau formation in pairwise thermal entanglement for fixed parameters of Hamiltonian in the case of the ferromagnetic and anti-ferromagnetic interactions. We also observe an unexpected critical point at finite temperature in the thermal entanglement of the spins (1/2,1) for antiferromagnetic case while the entanglement of the spins (1/2,1) for ferromagnetic case and the entanglement of the spins (1/2,1/2) for both ferromagnetic and antiferromagnetic cases almost decays exponentially to zero with increasing temperature. The critical point in entanglement of the spins (1/2,1) for antiferromagnetic case may be signature of the quantum phase transition at finite temperature.Comment: 7 pages, 9 figure

Thermal entanglement in the mixed three-spin X X Z Heisenberg model on a triangular cell

We numerically investigate thermal entanglement of the spins (1/2,1) and (1/2,1/2) in the three-mixed (1/2,1,1/2) anisotropic Heisenberg XXZ spin system on a simple triangular cell under an inhomogeneous magnetic field. We show that the external magnetic field induces strong plateau formation in pairwise thermal entanglement for fixed parameters of Hamiltonian in the case of the ferromagnetic and anti-ferromagnetic interactions. We also observe an unexpected critical point at finite temperature in the thermal entanglement of the spins (1/2,1) for antiferromagnetic case while the entanglement of the spins (1/2,1) for ferromagnetic case and the entanglement of the spins (1/2,1/2) for both ferromagnetic and antiferromagnetic cases almost decays exponentially to zero with increasing temperature. We conclude that this critical point in entanglement of the spins (1/2,1) for antiferromagnetic case indicates the presence of the quantum phase transition at finite temperature

Quantum heat engine model of mixed triangular spin system as a working substance

In this work, we consider a Heisenberg XXZ mixed (1/2, 1, 1/2) spin system on a triangular cell. We briefly summarize the theoretical framework. Then, we compute the energy eigenvalues for all eigenstates of the Hamiltonian model and we set a four-stroke Otto cycle to depend on the thermodynamical cycle based on the theoretical framework. In the numerical procedure, based on eigenenergies of the system, we compute the work and the efficiency for different spin interaction couplings for the four-stroke quantum Otto cycle. We show that the Heisenberg XXZ mixed spin model produce positive work and efficiency, when the system is coupled to an oscillating heat bath reservoir. Finally, we investigate magnetic field dependence of the work for several spin coupling and discuss all the results. (C) 2018 Elsevier B.V. All rights reserved

Entanglement in (1/2,1) Mixed-Spin XY Model with Long-Range Interaction

In this study, we investigate entanglement in a two mixed-spin (1/2,1) XY Heisenberg spin system under an applied magnetic field by considering the long-range interaction with an inverse-square function. The spin-spin coupling constant is considered as a function of the distance between spins. We also discuss the temperature and magnetic field dependence of the thermal entanglement in this system for this interaction. The numerical results show that, in the presence of the long-range interaction, thermal entanglement between spins has a rich behavior dependent upon the interaction strength, temperature and magnetic field. We find that for less than a critical distance there are entanglement plateaus dependent upon the distance between spins, whereas above the critical distance the entanglement can exhibit sudden death