Brandner Kay, Maisi Ville F, Pekola Jukka P, Garrahan Juan P, Flindt Christian
Low Temperature Laboratory, Department of Applied Physics, Aalto University, 00076 Aalto, Finland.
Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark.
Phys Rev Lett. 2017 May 5;118(18):180601. doi: 10.1103/PhysRevLett.118.180601. Epub 2017 May 4.
Statistical physics provides the concepts and methods to explain the phase behavior of interacting many-body systems. Investigations of Lee-Yang zeros-complex singularities of the free energy in systems of finite size-have led to a unified understanding of equilibrium phase transitions. The ideas of Lee and Yang, however, are not restricted to equilibrium phenomena. Recently, Lee-Yang zeros have been used to characterize nonequilibrium processes such as dynamical phase transitions in quantum systems after a quench or dynamic order-disorder transitions in glasses. Here, we experimentally realize a scheme for determining Lee-Yang zeros in such nonequilibrium settings. We extract the dynamical Lee-Yang zeros of a stochastic process involving Andreev tunneling between a normal-state island and two superconducting leads from measurements of the dynamical activity along a trajectory. From the short-time behavior of the Lee-Yang zeros, we predict the large-deviation statistics of the activity which is typically difficult to measure. Our method paves the way for further experiments on the statistical mechanics of many-body systems out of equilibrium.
统计物理提供了解释相互作用多体系统相行为的概念和方法。对有限尺寸系统中自由能的李 - 杨零点——复奇点——的研究，已促成对平衡相变的统一理解。然而，李和杨的思想并不局限于平衡现象。最近，李 - 杨零点已被用于刻画非平衡过程，诸如量子系统猝灭后的动力学相变或玻璃中的动力学有序 - 无序转变。在此，我们通过实验实现了一种在这种非平衡环境中确定李 - 杨零点的方案。我们从沿轨迹的动力学活性测量中提取了一个涉及正常态岛与两个超导引线之间安德列夫隧穿的随机过程的动力学李 - 杨零点。从李 - 杨零点的短时间行为，我们预测了通常难以测量的活性的大偏差统计。我们的方法为进一步开展非平衡多体系统统计力学实验铺平了道路。
