Employing the I-concurrence (Ic) measure, entanglement dynamics of superposition of isospin fermionic coherent states (SFCS) in Heisenberg spin chains of Ising, XX, XXX and XXZ models in the presence of Dzyaloshinskii–Moriya (DM) interaction and magnetic field is studied. For the above-mentioned models, the entanglement dynamics of SFCSs is independent of magnetic field effect and the DM interaction effect introduces the quantum fluctuations in the entanglement dynamics of the system. It is shown that depending on the choice of the models in the absence of DM interaction, entanglement dynamics alter by applying and increasing the magnetic field to the first (second) part of the system. We showed that by increasing the spin of the fermionic coherent states (j) and, consequently, increasing their dimension d = 2j + 1, the entanglement dynamics of the SFCS states sharply increases and fluctuates at a higher level. Our results indicate no entanglement sudden death phenomenon under the examined conditions.
Employing the I-concurrence (Ic) measure, entanglement dynamics of superposition of isospin fermionic coherent states (SFCS) in Heisenberg spin chains of Ising, XX, XXX and XXZ models in the presence of Dzyaloshinskii–Moriya (DM) interaction and magnetic field is studied. For the above-mentioned models, the entanglement dynamics of SFCSs is independent of magnetic field effect and the DM interaction effect introduces the quantum fluctuations in the entanglement dynamics of the system. It is shown that depending on the choice of the models in the absence of DM interaction, entanglement dynamics alter by applying and increasing the magnetic field to the first (second) part of the system. We showed that by increasing the spin of the fermionic coherent states (j) and, consequently, increasing their dimension d = 2j + 1, the entanglement dynamics of the SFCS states sharply increases and fluctuates at a higher level. Our results indicate no entanglement sudden death phenomenon under the examined conditions.
With considering the intrinsic decoherence, the dynamic behaviors of quantum entanglement in a three-qubit XXZ Heisenberg system with Dzyaloshinskii-Moriya (DM) interaction and anisotropy for different initial states are investigated. The research result shows that the anisotropy parameter does not affect the system entanglement, however, the intrinsic decoherence has obvious inhibitory effect on entanglement. When the initial state of system is an entangled state, we can obtain the stable value of entanglement by adjusting DM interaction parameters appropriately. As the system initial state is a separation state, entanglement oscillates, and the amplitude of oscillation decays with time periodically, and there will appear the death phenomenon after each oscillation, and with time going on, its concurrence will be zero. When the initial state is entangled, by choosing the proper DM parameter, the three pairs of entanglements oscillate with time and eventually approach to a steady value. The increase of accelerates the decay of concurrence. When the initial state is separated, entanglement oscillates, and the amplitude of oscillation decays with time periodically, and there will appear the death phenomenon after each oscillation, with time going on, its concurrence will be zero. Therefore, the proper initial state and DM interaction parameters can control the concurrence effectively under the intrinsic decoherence, thereby obtaining the preferable entanglement resource.
This paper investigates the entanglement dynamics of the system, composed of two qubits A and B with Heisenberg XX spin interactation. There is a third controller qubit C, which only has Dzyaloshinskii–Moriya (DM) spin-orbit interaction with the qubit B. It is found that depending on the initial state of the controller qubit C and DM interaction, the entanglement of the system displays amplification and sudden birth effects. These effects indicate that one can control the entanglement of the system, which may be helpful for quantum information processing.
Dynamics of the nearest-neighbor concurrence and the block–block entanglement in closed Heisenberg chains with Dzyaloshinskii–Moriya (DM) interactions are simulated numerically. It is found that the nearest-neighbor concurrence and the block–block entanglement can be generated dynamically from an initial antiferromagnetic (AF) state, and DM interactions will enhance the amplitude of oscillation of concurrence and that of block–block entanglement. Furthermore, dynamics of block–block entanglement SL in the chain with even number spins is coincident with the dynamics of SN - L for D = 0. However, with the consideration of DM interactions, the evolution of SL will not be consistent with that of SN - L for the chain with odd number spins. In a given time interval, the maximal value of the generated nearest-neighbor concurrence [Formula: see text] will first decrease with the increase of chain's length, then oscillate with the increase of N. The maximal value and the minimal value of the oscillation becomes stable for a large N, and [Formula: see text] of the chain with odd spins is larger than that of the chain with even spins for a large N. The influence of DM interaction on the value of [Formula: see text] becomes unobvious with the increase of chain's length.
By using the density-matrix renormalization group method, the spin entanglement in the antiferromagnetic Heisenberg chain with the staggered Dzyaloshinskii-Moriya (DM) interactions is investigated. It is found that the staggered DM interactions remove the field-induced second order quantum phase transition of the system at the magnitude of magnetic field H＝2, and lead to the vanishing of the anomalous behavior of quantum entanglement. Also, the staggered DM interactions eliminate the divergence of entanglement range. It means the disappearance of the factorizing point in the model studied. Due to the presence of the staggered DM interactions, the system will never come to the state of saturated ferromagnetism under finite magnetic fields, thus maintaining the spin entanglement. The staggered DM interactions favor the tuning of the strength and range of spin entanglement.
We investigate the thermal entanglement in a spin-1/2 Ising–Heisenberg diamond chain, in which the vertical Heisenberg spin dimers alternate with single Ising spins. Due to the fact that the Dzyaloshinskii–Moriya (DM) interaction contributes to unusual and interesting magnetic properties in actual materials, and moreover it plays a significant role in the degree of the entanglement of the Heisenberg quantum spin systems, we focus on the effects of different DM interactions, including D z and D x , on the thermal entanglement of the Heisenberg spin dimer. The concurrence, as a measure of spin dimer entanglement, is calculated for different values of exchange interactions, DM interaction, external magnetic field, and temperature. It is found that the critical temperature and the critical magnetic field corresponding to the vanishing of entanglement increase with DM interaction, and the entanglement revival region gets larger by increasing DM interaction, thus DM interaction favors the formation of the thermal entanglement. It is observed that different DM interaction parameters ( D z and D x ) have remarkably different influences on the entanglement. Different from the case D z , there is the non-monotonic variation of the concurrence with temperature in the case D x , and additionally the DM interaction D x can induce the entanglement near zero temperature in the case that the antiferromagnetic Ising-type interaction constant is larger than the antiferromagnetic Heisenberg interaction constant. It is also shown that for the same value of DM interaction the critical magnetic field of the case D x is larger than that of the case D z .
We investigate the exact entanglement dynamics of a two-qubit Heisenberg XXZ chain with Dzyaloshinskii-Moriya (DM) interactions, interacting with an anisotropic spin bath in thermal equi- librium at a temperature T, driven by an external magnetic field B along the z-axis. We establish that, for an initially entangled qubit pair, the DM interactions generate entanglement and enhance the entanglement in the revival region. The effects of the DM interaction are also seen to be very important at high temperatures and for weak coupling between the two qubits where it is seen to preserve entanglement. These effects are weakened when the magnetic field B and the Heisenberg coupling are switched on. If the two-qubits are prepared in an initially separable state, the DM in- teraction instead has a negative effect on their entanglement. On a whole entanglement can better be preserve in the spin chain even at high temperatures by increases the external magnetic field B and the Heisenberg couplings, and by tuning the strength of the DM interaction.