First experimental tests towards cavity-enhanced ferroelectricity

Strong coupling of light and matter has been a fruitful research topic in condensed matter physics in the last years. Inside an optical cavity, some effects of strong coupling can appear even "in the dark", i.e. without any external drive but using only the fluctuations of the eigenmodes of the cavity. Our project aims to modify physical properties of functional materials using this phenomenon.

A recent theoretical work by Y. Ashida et al. (arXiv:2003.13695) suggests that an infrared cavity could enhance the phase transition temperature of a ferroelectric material, as well as induce ferroelectricity in "quantum paraelectric" materials such as SrTiO₃. It proposes a plane-parallel cavity with two metallic mirrors in direct contact with the functional material layer. This geometry is identical to that of a parallel-plate capacitor. The predicted magnitude of the effect depends on the plasma frequency of the metal layers.

We will present dielectric measurements performed on SrTiO₃ single-crystals as well as on ferroelectric (Pb,Sr)TiO₃ epitaxial thin films using electrodes with different plasma frequencies, and discuss the relevance of our results in the context of light-matter coupling.