Nonequilibrium Phase Transition in a Two-Dimensional Driven Open Quantum System
Nonequilibrium Phase Transition in a Two-Dimensional Driven Open Quantum System
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DOI：
10.1103/physrevx.5.041028
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发表时间：
2015-11-17
影响因子：
12.5
通讯作者：
Szymanska, M. H.
中科院分区：
文献类型：
--
作者：
Dagvadorj, G.;Fellows, J. M.;Szymanska, M. H.
Berezinskiiii-Kosterlitz-无边界机制（英语：Berezinskiii-Kosterlitz-无边界机制），其中相变是由拓扑缺陷的扩散所介导的，控制着广泛的具有连续对称性的平衡二维系统的临界行为，从自旋系统到超导薄膜和二维玻色流体，如液氦和超冷原子。我们在这里表明，这种现象并不局限于热平衡，而更普遍地生存在一个耗散的高度非平衡系统驱动到一个稳定的状态。通过考虑实验相关的大小的极化激元的量子流体，在所谓的光学参量振荡器制度，我们证明，它确实经历了一个与涡旋绑定-解除绑定机制相关联的相变。然而，在（代数）有序相的一阶相关函数的幂律衰减的指数可以超过平衡上限：这表明驱动耗散系统的有序相可以维持更高水平的集体激发之前，秩序被破坏的拓扑缺陷。我们的工作表明，最近在相互作用的二维光-物质系统中观察到的宏观相干现象，是由Berezinskiii-Kosterlitz-Einstein非平衡相变引起的，而不是玻色-爱因斯坦凝聚类型。
The Berezinskii-Kosterlitz-Thouless mechanism, in which a phase transition is mediated by the proliferation of topological defects, governs the critical behavior of a wide range of equilibrium two-dimensional systems with a continuous symmetry, ranging from spin systems to superconducting thin films and two-dimensional Bose fluids, such as liquid helium and ultracold atoms. We show here that this phenomenon is not restricted to thermal equilibrium, rather it survives more generally in a dissipative highly nonequilibrium system driven into a steady state. By considering a quantum fluid of polaritons of an experimentally relevant size, in the so-called optical parametric oscillator regime, we demonstrate that it indeed undergoes a phase transition associated with a vortex binding-unbinding mechanism. Yet, the exponent of the power-law decay of the first-order correlation function in the (algebraically) ordered phase can exceed the equilibrium upper limit: this shows that the ordered phase of driven-dissipative systems can sustain a higher level of collective excitations before the order is destroyed by topological defects. Our work suggests that the macroscopic coherence phenomena, observed recently in interacting two-dimensional light-matter systems, result from a nonequilibrium phase transition of the Berezinskii-Kosterlitz-Thouless rather than the Bose-Einstein condensation type.