Quantum correlation and entanglement in the Heisenberg model with biquadratic interaction on square lattice

Abstract

We study the bipartite entanglement as well as the correlation content between two partitions of the quantum 2D Heisenberg model with biquadratic interactions, where the $$\theta $$ parameter controls the ratio of the biquadratic and exchange couplings. We also investigate the pairwise entanglement between nearest-neighbor qubits. The calculations were performed for the model on square lattice, in the Neel phase and ferroquadrupolar phase using spin wave theory and Schwinger boson approaches. In the Neel phase that corresponds to range $$-\pi<\theta <0$$ , we use the Dyson–Maleev representation and SU(2) Schwinger boson representation to calculate the von Neumann entropy as function of the biquadratic coupling $$J_\mathrm{{bq}}$$ . In the ferroquadrupolar phase, we use the SU(3) Schwinger boson representation which is adequate to treat this phase.