Qualitatively different decaying behaviors of the quantum Loschmidt echo in the two phases of the LMG model

首发时间:2013-12-12
Abstract:A unified expression of the quantum Loschmidt echo (LE) in the vicinity of the quantum phase transition in the Lipkin-Meshkov-Glick model is derived, which is valid both in the symmetric phase and in the broken phase. The LE shows qualitatively different decaying behaviors in the two phases, in particular, in the broken phase, it has a decay rate that diverges in the thermodynamic limit. In contrast to many-body systems, in which the LE also shows divergent decay rates in the thermodynamic limit due to the so-called orthogonality catastrophe, the considered motion in this model has a classical counterpart with one degree of freedom only.
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洛施密特回波(Loschmidt echo)在 Lipkin-Meshkov-Glick 模型两相中的不同衰减行为
摘要:在 Lipkin-Meshkov-Glick (LMG) 模型的量子相变点附近导出了在对称相与破缺相都适用的 Loschmidt echo (LE) 的一个统一的解析表达式。发现 LE 在不同的相呈现不同的衰减行为,尤其是在破缺相,LE 的衰减率在热力学极限下是发散的。对比于多体系统,在那些系统中的 LE 的衰减率在热力学极限下由于正交性灾难 (orthogonality catastrophe) 的原因也将发散,然而对于 LMG 模型来说其经典对应仅有一个自由度。
关键词: 量子相变,Lipkin-Meshkov-Glick (LMG) 模型,洛施密特回波(Loschmidt echo),Holstein-Primakoff 变换,衰减行为,衰减率
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