Stepanov Petr, Amelio Ivan, Rousset Jean-Guy, Bloch Jacqueline, Lemaître Aristide, Amo Alberto, Minguzzi Anna, Carusotto Iacopo, Richard Maxime
Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, 38000, Grenoble, France.
INO-CNR BEC Center and Dipartimento di Fisica, Universita` di Trento, 38123, Povo, Italy.
Nat Commun. 2019 Aug 27;10(1):3869. doi: 10.1038/s41467-019-11886-3.
Exciton-polaritons in semiconductor microcavities constitute the archetypal realization of a quantum fluid of light. Under coherent optical drive, remarkable effects such as superfluidity, dark solitons or the nucleation of vortices have been observed, and can be all understood as specific manifestations of the condensate collective excitations. In this work, we perform a Brillouin scattering experiment to measure their dispersion relation [Formula: see text] directly. The results, such as a speed of sound which is apparently twice too low, cannot be explained upon considering the polariton condensate alone. In a combined theoretical and experimental analysis, we demonstrate that the presence of an excitonic reservoir alongside the polariton condensate has a dramatic influence on the characteristics of the quantum fluid, and explains our measurement quantitatively. This work clarifies the role of such a reservoir in polariton quantum hydrodynamics. It also provides an unambiguous tool to determine the condensate-to-reservoir fraction in the quantum fluid, and sets an accurate framework to approach ideas for polariton-based quantum-optical applications.
半导体微腔中的激子极化激元构成了光量子流体的典型实例。在相干光驱动下，人们观察到了诸如超流性、暗孤子或涡旋成核等显著效应，并且这些效应都可以理解为凝聚集体激发的特定表现形式。在这项工作中，我们进行了布里渊散射实验，以直接测量它们的色散关系[公式：见原文]。诸如声速明显低两倍的结果，仅考虑极化激元凝聚体是无法解释的。在理论与实验相结合的分析中，我们证明了在极化激元凝聚体旁边存在激子库对量子流体的特性有显著影响，并对我们的测量结果进行了定量解释。这项工作阐明了这种库在极化激元量子流体动力学中的作用。它还提供了一个明确的工具来确定量子流体中凝聚体与库的比例，并为基于极化激元的量子光学应用理念提供了一个准确的框架。
