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Paper   IPM / Physic / 11438
School of Physics
  Title:   Thermodynamic Bbehavior of the XXZ Heisenebrg s=1/2 Chain Around the Factorizing Magnetic Field
1.  J. Abouie
2.  A. Langari
3.  M. Siahatgar
  Status:   Published
  Journal: J. Physics: Condens. Matter
  Vol.:  22
  Year:  2010
  Pages:   216008
  Supported by:  IPM
We have investigated the zero and finite temperature behaviors of the anisotropic antiferromagnetic Heisenberg XXZ spin-1/2 chain in the presence of a transverse magnetic field (h). The attention is concentrated on an interval of magnetic field between the factorizing field (hf) and the critical one (hc). The model presents a spin-flop phase for 0 < h < hf with an energy scale which is defined by the long range antiferromagnetic order while it undergoes an entanglement phase transition at h=hf. The entanglement estimators clearly show that the entanglement is lost exactly at h=hf which justifies different quantum correlations on both sides of the factorizing field. As a consequence of zero entanglement (at h=hf) the ground state is known exactly as a product of single particle states which is the starting point for initiating a spin wave theory. The linear spin wave theory is implemented to obtain the specific heat and thermal entanglement of the model in the interested region. A double peak structure is found in the specific heat around h=hf which manifests the existence of two energy scales in the system as a result of two competing orders before the critical point. These results are confirmed by the low temperature Lanczos data which we have computed.

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