Department of Physics, Shahrood University of Technology, Shahrood 36199-95161, Iran.
J Phys Condens Matter. 2010 Jun 2;22(21):216008. doi: 10.1088/0953-8984/22/21/216008. Epub 2010 May 5.
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 (h(f)) and the critical one (h(c)). The model presents a spin-flop phase for 0 < h < h(f) with an energy scale which is defined by the long range antiferromagnetic order while it undergoes an entanglement phase transition at h = h(f). The entanglement estimators clearly show that the entanglement is lost exactly at h = h(f), which justifies different quantum correlations on both sides of the factorizing field. As a consequence of zero entanglement (at h = h(f)) 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 = h(f), 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.
我们研究了存在横向磁场（h）时各向异性反铁磁海森堡 XXZ 自旋 1/2 链的零温和有限温行为。注意力集中在因子化场（h(f)）和临界场（h(c)）之间的磁场间隔内。对于 0 < h < h(f)，模型呈现出自旋翻转相，其能量标度由长程反铁磁序定义，而在 h = h(f)时经历纠缠相变。纠缠估计器清楚地表明，纠缠在 h = h(f)处完全丢失，这证明了因子化场两侧存在不同的量子相关性。由于零纠缠（在 h = h(f)处），基态可以精确地表示为单粒子态的乘积，这是启动自旋波理论的起点。我们实施线性自旋波理论来获得模型在感兴趣区域的比热和热纠缠。在 h = h(f)附近的比热中发现了双峰结构，这表明在临界点之前存在两个竞争的顺序，导致系统中有两个能量标度。我们计算的低温 Lanczos 数据证实了这些结果。
