Collective fluid dynamics of a polariton condensate in a semiconductor microcavity
Collective fluid dynamics of a polariton condensate in a semiconductor microcavity
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DOI：
10.1038/nature07640
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发表时间：
2009-01-15
期刊：
影响因子：
64.8
通讯作者：
Vina, L.
中科院分区：
文献类型：
--
作者：
Amo, A.;Sanvitto, D.;Vina, L.
半导体微腔提供了研究弱相互作用玻色子物理的独特系统。它们的基元激发，极化激元-激子和光子的混合物-可以在宏观简并态中积累，在非相干（1，2）或相干（3，4）激发下形成各种类型的实验配置中的凝聚体。极化激元的凝聚体已经被提出作为超流性的候选者（5，6），并且涡旋的形成（7）以及具有线性色散的元激发（8）被积极地寻求作为支持这一点的证据。在这里，使用由短光脉冲触发的相干激发，我们已经创建并设置在运动中的极化激元的宏观简并状态，可以使其与存在于微腔中的各种缺陷碰撞。我们的实验显示了一个相干光-物质包的惊人表现，它以高速（光速的百分之一）行进，并显示出与超流一致的集体动力学，尽管它具有非常不寻常的特征，因为它涉及一个非平衡耗散系统。我们的主要结果是观察到的线性极化激元色散伴随着无扩散运动;流动没有阻力时，穿越障碍物;抑制瑞利散射;分裂成两种流体时，障碍物的大小是可比的波包的大小。这一工作为研究非平衡凝聚体的新现象开辟了道路.
Semiconductor microcavities offer unique systems in which to investigate the physics of weakly interacting bosons. Their elementary excitations, polaritons - mixtures of excitons and photons - can accumulate in macroscopically degenerate states to form various types of condensate in a wide range of experimental configurations, under either incoherent(1,2) or coherent(3,4) excitation. Condensates of polaritons have been put forward as candidates for superfluidity(5,6), and the formation of vortices(7) as well as elementary excitations with linear dispersion(8) are actively sought as evidence to support this. Here, using a coherent excitation triggered by a short optical pulse, we have created and set in motion a macroscopically degenerate state of polaritons that can be made to collide with a variety of defects present in the microcavity. Our experiments show striking manifestations of a coherent light - matter packet, travelling at high speed ( of the order of one per cent of the speed of light) and displaying collective dynamics consistent with superfluidity, although one of a highly unusual character as it involves an out- of- equilibrium dissipative system. Our main results are the observation of a linear polariton dispersion accompanied by diffusionless motion; flow without resistance when crossing an obstacle; suppression of Rayleigh scattering; and splitting into two fluids when the size of the obstacle is comparable to the size of the wave packet. This work opens the way to the investigation of new phenomenology of out- of- equilibrium condensates.