Phonon polaritons are hybrid states of light and matter that are typically realised when optically active phonons couple strongly to photons. We suggest a new approach to realising phonon polaritons, by employing a transverse-pumping Raman scheme, as used in experiments on cold atoms in optical cavities. This approach allows hybridisation between an optical cavity mode and any Raman-active phonon mode. Moreover, this approach enables one to tune the effective phonon–photon coupling by changing the strength of the transverse pumping light. We show that such a system may realise a phonon-polariton condensate. To do this, we find the stationary states and use Floquet theory to determine their stability. We thus identify distinct superradiant and lasing states in which the polariton modes are macroscopically populated. We map out the phase diagram of these states as a function of pump frequencies and strengths. Using parameters for transition metal dichalcogenides, we show that realisation of these phases may be practicably obtainable. The ability to manipulate phonon mode frequencies and attain steady-state populations of selected phonon modes provides a new tool for engineering correlated states of electrons.

声子极化激元是光和物质的混合状态，通常在光活性声子与光子强烈耦合时实现。我们提出了一种实现声子极化激元的新方法，通过采用横向泵浦拉曼方案，就像在光腔中的冷原子实验中使用的那样。这种方法允许光腔模式和任何拉曼有源声子模式之间的混合。此外，这种方法使人们可以通过改变横向泵浦光的强度来调整有效的声子-光子耦合。我们表明，这样的系统可以实现声子极化激元凝聚物。为此，我们找到稳态并使用 Floquet 理论来确定它们的稳定性。因此，我们确定了极化激元模式在宏观上填充的不同超辐射和激光状态。我们绘制了这些状态的相位图，作为泵浦频率和强度的函数。使用过渡金属二硫化物的参数，我们表明这些相的实现是可行的。操纵声子模式频率并获得选定声子模式的稳态群的能力为工程电子的相关状态提供了一种新工具。