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arXiv 1701.05552cond-mat.stat-mechquant-ph
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低温预热化:长程序的气味

Prethermalization at Low Temperature: the Scent of Long-Range Order

Vincenzo Alba, Maurizio Fagotti

摘要:

孤立多体量子系统中的非平衡时间演化通常导致热化。然而,弛豫过程可能非常缓慢,并且在中间时间经常观察到准静态非热平台。典型的例子是可积模型中的量子猝灭,在很长一段时间内,状态无法逃脱近似可积性所施加的约束。我们揭示了一个新的机制的预热化,基于存在的对称性的预淬火哈密顿量,这是自发打破在零温度下,明确打破后淬火哈密顿量。该现象的典型时间尺度与初始状态的热关联长度成比例,其随着温度的降低而发散。我们证明了预热准定态可以近似为违反簇分解性质的混合态。我们考虑两个例子:横场伊辛链,其中的全部时间演化计算解析,和(不可积)ANNNI模型,这是数值研究。

英文摘要:

Non-equilibrium time evolution in isolated many-body quantum systems generally results in thermalization. However, the relaxation process can be very slow, and quasi-stationary non-thermal plateaux are often observed at intermediate times. The paradigmatic example is a quantum quench in an integrable model with weak integrability breaking; for a long time, the state can not escape the constraints imposed by the approximate integrability. We unveil a new mechanism of prethermalization, based on the presence of a symmetry of the pre-quench Hamiltonian, which is spontaneously broken at zero temperature and is explicitly broken by the post-quench Hamiltonian. The typical time scale of the phenomenon is proportional to the thermal correlation length of the initial state, which diverges as the temperature is lowered. We show that the prethermal quasi-stationary state can be approximated by a mixed state that violates cluster decomposition property. We consider two examples: the transverse-field Ising chain, where the full time evolution is computed analytically, and the (non integrable) ANNNI model, which is investigated numerically.

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