Universal dynamics in an isolated one-dimensional Bose gas far from equilibrium
Universal dynamics in an isolated one-dimensional Bose gas far from equilibrium
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DOI：
10.1038/s41586-018-0667-0
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发表时间：
2018-11-08
期刊：
影响因子：
64.8
通讯作者：
Schmiedmayer, Joerg
中科院分区：
文献类型：
--
作者：
Erne, Sebastian;Buecker, Robert;Schmiedmayer, Joerg
了解远离平衡的孤立量子系统的行为及其平衡是量子多体物理学中最紧迫的问题之一（1，2）。有强有力的理论证据表明，远离平衡的各种各样的系统，包括早期宇宙膨胀后（3-6），夸克胶子物质产生的重离子碰撞（7-9），和冷量子气体（4，10 -14），在其演化过程中表现出普遍的时间和空间标度，独立于其初始状态或微尺度属性。然而，缺乏直接的实验证据。在这里，我们展示了一个孤立的，远离平衡，一维玻色气体，出现从一个三维的超冷玻色气体通过一个强大的冷却淬火的时间演化的动量分布的普遍缩放。在标度范围内，系统在低动量下的时间演化可用一个与时间无关的普适函数和一个标度指数来描述。非平衡标度描述了一个新出现的守恒量向低动量的输运，最终导致准凝聚的形成。我们的研究结果建立了一个孤立的量子多体系统中的普遍标度动力学，这是一个关键的一步，表征时间演化远离平衡的普适性类。普适性将开启使用的可能性，例如，在最低能量的冷原子装置，以模拟目前无法达到的系统在最高能量的动力学的重要方面，如在暴胀的早期宇宙中遇到的。
Understanding the behaviour of isolated quantum systems far from equilibrium and their equilibration is one of the most pressing problems in quantum many-body physics(1,2). There is strong theoretical evidence that sufficiently far from equilibrium a wide variety of systems-including the early Universe after inflation(3-6) quark-gluon matter generated in heavy-ion collisions(7-9), and cold quantum gases(4 ,10-14)- exhibit universal scaling in time and space during their evolution, independent of their initial state or microscale properties. However, direct experimental evidence is lacking. Here we demonstrate universal scaling in the time-evolving momentum distribution of an isolated, far-from-equilibrium, onedimensional Bose gas, which emerges from a three-dimensional ultracold Bose gas by means of a strong cooling quench. Within the scaling regime, the time evolution of the system at low momenta is described by a time-independent, universal function and a single scaling exponent. The non-equilibrium scaling describes the transport of an emergent conserved quantity towards low momenta, which eventually leads to the build-up of a quasi-condensate. Our results establish universal scaling dynamics in an isolated quantum many-body system, which is a crucial step towards characterizing time evolution far from equilibrium in terms of universality classes. Universality would open the possibility of using, for example, coldatom set-ups at the lowest energies to simulate important aspects of the dynamics of currently inaccessible systems at the highest energies, such as those encountered in the inflationary early Universe.