Bogoliubov excitations of a polariton condensate in dynamical equilibrium with an incoherent reservoir
Bogoliubov excitations of a polariton condensate in dynamical equilibrium with an incoherent reservoir
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DOI：
10.1103/physrevb.105.224515
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发表时间：
2022-06-29
影响因子：
3.7
通讯作者：
Parish, M. M.
中科院分区：
文献类型：
--
作者：
Pieczarka, M.;Bleu, O.;Parish, M. M.
经典的Bogoliubov弱相互作用玻色气体理论基于这样的假设，即几乎所有的玻色子都在足够低的温度下凝聚成最低的量子态。在这里，我们发展了Bogoliubov理论的一个推广版本，适用于具有大的非相干非凝聚组分的驱动耗散激子-极化凝聚体或激子库的情况。我们认为这样的库既可以由激子高动量极化子组成，也可以由不同光学活性层上激子的光学暗叠加组成，例如一个微腔中的多个量子阱。特别是，我们预测了暗激子态和亮激子态(光耦合)之间的相互转换，这可能导致凝聚态和储集态之间的动态平衡。我们表明，由于极化子的非伽利略不变性质，储存库的存在从根本上改变了Bogoliubov准粒子激发的能量和幅度。我们的实验支持了我们的理论发现，在高密度区域，我们直接探测到了光陷极化子凝聚体的Bogoliubov激发分支。通过对测量的激发分支占位的分析，我们提取了一定动量范围内的Bogoliubov振幅，并表明它们与我们的广义理论是一致的。
The classic Bogoliubov theory of weakly interacting Bose gases rests upon the assumption that nearly all the bosons condense into the lowest quantum state at sufficiently low temperatures. Here we develop a generalized version of Bogoliubov theory for the case of a driven-dissipative exciton-polariton condensate with a large incoherent uncondensed component, or excitonic reservoir. We argue that such a reservoir can consist of both excitonic high-momentum polaritons and optically dark superpositions of excitons across different optically active layers, such as multiple quantum wells in a microcavity. In particular, we predict interconversion between the dark and bright (light-coupled) excitonic states that can lead to a dynamical equilibrium between the condensate and reservoir populations. We show that the presence of the reservoir fundamentally modifies both the energy and the amplitudes of the Bogoliubov quasiparticle excitations due to the non-Galilean-invariant nature of polaritons. Our theoretical findings are supported by our experiment, where we directly detect the Bogoliubov excitation branches of an optically trapped polariton condensate in the high-density regime. By analyzing the measured occupations of the excitation branches, we extract the Bogoliubov amplitudes across a range of momenta and show that they agree with our generalized theory.