外磁场对反铁磁环境中中心自旋退相干的影响
Influence of an external magnetic field on the decoherence of a central spin coupled to an antiferromagnetic environment
摘要：
利用自旋波近似，研究了中心自旋与反铁磁耦合系统在外加整体磁场作用下的退相干动力学。外部磁场通过对反铁磁环境的影响来影响退相干过程。结果表明，退相干因子随时间呈高斯衰减，它与反铁磁环境中的外部磁场和晶体各向异性场的强度有关。当外加磁场增大到反铁磁环境中自旋翻转（一阶量子相变）的临界点时，中心自旋的退相干达到最大值.这一结果与最近的几个量子相变见证研究是一致的。研究了环境温度对中心自旋退相干行为的影响。
英文摘要：
Using the spin wave approximation, we study the decoherence dynamics of a central spin coupled to an antiferromagnetic environment under the application of an external global magnetic field. The external magnetic field affects the decoherence process through its effect on the antiferromagnetic environment. It is shown explicitly that the decoherence factor which displays a Gaussian decay with time depends on the strength of the external magnetic field and the crystal anisotropy field in the antiferromagnetic environment. When the values of the external magnetic field is increased to the critical field point at which the spin-flop transition (a first-order quantum phase transition) happens in the antiferromagnetic environment, the decoherence of the central spin reaches its highest point. This result is consistent with several recent quantum phase transition witness studies. The influences of the environmental temperature on the decoherence behavior of the central spin are also investigated.
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