Universal prethermal dynamics of Bose gases quenched to unitarity
Universal prethermal dynamics of Bose gases quenched to unitarity
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DOI：
10.1038/s41586-018-0674-1
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发表时间：
2018-11-08
期刊：
影响因子：
64.8
通讯作者：
Hadzibabic, Zoran
中科院分区：
文献类型：
--
作者：
Eigen, Christoph;Glidden, Jake A. P.;Hadzibabic, Zoran
理解物质的强关联相，比如夸克 - 胶子等离子体和中子星，特别是这类系统的动力学，例如在哈密顿量猝变（某个哈密顿量参数的突然改变，比如粒子间相互作用的强度）之后的情况，是现代物理学中的一个基本挑战。超冷原子气体由于其粒子间相互作用可调且具有实验上可分辨的固有时间尺度，是研究这些问题的极佳量子模拟器。特别是，它们提供了进入幺正区域的途径，在该区域中相互作用的强度达到量子力学所允许的极限。这个区域在费米气体中已被广泛研究（1,2）。研究较少的幺正玻色气体（3 - 11）提供了一些可能性（12），比如仅由气体密度控制的普适物理（13,14）以及新形式的超流性（15 - 17）。在此，通过动量和时间分辨研究，我们探究了猝变到幺正性的简并和热均匀玻色气体。在简并样本中，我们观察到与预热态（18 - 24）的出现相符的普适猝变后动力学，且具有普适的非零凝聚分数（22,24）。在热气体中，动力学和热力学性质通常取决于气体密度和温度，但我们发现它们仍然可以用普适的无量纲函数来表示。令人惊讶的是，我们发现总猝变诱导的关联能与气体温度无关。这些测量为幺正玻色气体理论提供了定量的基准和挑战。
Understanding strongly correlated phases of matter, such as the quark-gluon plasma and neutron stars, and in particular the dynamics of such systems, for example, following a Hamiltonian quench (a sudden change in some Hamiltonian parameter, such as the strength of interparticle interactions) is a fundamental challenge in modern physics. Ultracold atomic gases are excellent quantum simulators for these problems, owing to their tunable interparticle interactions and experimentally resolvable intrinsic timescales. In particular, they provide access to the unitary regime, in which the interactions are as strong as allowed by quantum mechanics. This regime has been extensively studied in Fermi gases(1,2). The less-explored unitary Bose gases(3-11) offer possibilities(12) such as universal physics controlled solely by the gas density(13,14) and new forms of superfluidity(15-17). Here, through momentum- and time-resolved studies, we explore degenerate and thermal homogeneous Bose gases quenched to unitarity. In degenerate samples, we observe universal post-quench dynamics in agreement with the emergence of a prethermal state(18-24)( )with a universal non-zero condensed fraction(22,24). In thermal gases, the dynamic and thermodynamic properties generally depend on the gas density and the temperature, but we find that they can still be expressed in terms of universal dimensionless functions. Surprisingly, we find that the total quench-induced correlation energy is independent of the gas temperature. These measurements provide quantitative benchmarks and challenges for the theory of unitary Bose gases.