Alyatkin S, Sigurdsson H, Askitopoulos A, Töpfer J D, Lagoudakis P G
Center for Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, Moscow, Russia.
Laboratories for Hybrid Photonics, Skolkovo Institute of Science and Technology, Moscow, Russia.
Nat Commun. 2021 Sep 22;12(1):5571. doi: 10.1038/s41467-021-25845-4.
One of the recently established paradigms in condensed matter physics is examining a system's behaviour in artificial potentials, giving insight into phenomena of quantum fluids in hard-to-reach settings. A prominent example is the matter-wave scatterer lattice, where high energy matter waves undergo transmission and reflection through narrow width barriers leading to stringent phase matching conditions with lattice band formation. In contrast to evanescently coupled lattice sites, the realisation of a scatterer lattice for macroscopic matter-wave fluids has remained elusive. Here, we implement a system of exciton-polariton condensates in a non-Hermitian Lieb lattice of scatterer potentials. By fine tuning the lattice parameters, we reveal a nonequilibrium phase transition between distinct regimes of polariton condensation: a scatterer lattice of gain guided polaritons condensing on the lattice potential maxima, and trapped polaritons condensing in the potential minima. Our results pave the way towards unexplored physics of non-Hermitian fluids in non-stationary mixtures of confined and freely expanding waves.
凝聚态物理中最近建立的范式之一是研究系统在人工势场中的行为，从而深入了解在难以实现的条件下量子流体的现象。一个突出的例子是物质波散射晶格，其中高能物质波通过窄宽度势垒进行透射和反射，从而导致与晶格能带形成严格的相位匹配条件。与渐逝耦合的晶格位点不同，宏观物质波流体的散射晶格的实现仍然难以捉摸。在这里，我们在散射势的非厄米李晶格中实现了一个激子极化激元凝聚体系统。通过微调晶格参数，我们揭示了极化激元凝聚不同状态之间的非平衡相变：增益引导的极化激元的散射晶格在晶格势最大值处凝聚，而捕获的极化激元在势最小值处凝聚。我们的结果为在受限波和自由扩展波的非平稳混合中探索非厄米流体的未知物理铺平了道路。
