The ferroelectric photo ground state of SrTiO3: Cavity materials engineering

Proceedings Of The National Academy Of Sciences Of The United States Of America 118 (31), e2105618118 (2021)

The ferroelectric photo ground state of SrTiO3: Cavity materials engineering

Simone Latini, Dongbin Shin,Shunsuke A. Sato,Christian Schäfer,Umberto De Giovannini, Hannes Hübener, Angel Rubio

Optical cavities confine light on a small region in space, which can result in a strong coupling of light with materials inside the cavity. This gives rise to new states where quantum fluctuations of light and matter can alter the properties of the material altogether. Here we demonstrate, based on first-principles calculations, that such light–matter coupling induces a change of the collective phase from quantum paraelectric to ferroelectric in the SrTiO 3 SrTiO3 ground state, which has thus far only been achieved in out-of-equilibrium strongly excited conditions [X. Li et al., Science 364, 1079–1082 (2019) and T. F. Nova, A. S. Disa, M. Fechner, A. Cavalleri, Science 364, 1075–1079 (2019)]. This is a light–matter hybrid ground state which can only exist because of the coupling to the vacuum fluctuations of light, a photo ground state. The phase transition is accompanied by changes in the crystal structure, showing that fundamental ground state properties of materials can be controlled via strong light–matter coupling. Such a control of quantum states enables the tailoring of materials properties or even the design of novel materials purely by exposing them to confined light.

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We are grateful for the illuminating discussions with Dmitri Basov, Atac Imamoglu, Jerome Faist, Jean-Marc Triscone, Peter Littlewood, Andrew Millis, Michael Ruggenthaler, Michael A. Sentef, and Eugene Demler. We acknowledge financial support from the European Research Council (Grant ERC-2015-AdG-694097), Grupos Consolidados (Grant IT1249- 19), the Japan Society for the Promotion of Science KAKENHI program (Grant JP20K14382), and the Cluster of Excellence “CUI: Advanced Imaging of Matter” of the Deutsche Forschungsgemeinschaft (Grant EXC 2056 Project 390715994). The Flatiron Institute is a division of the Simons Foundation. S.L. and D.S. acknowledge support from the Alexander von Humboldt Foundation.

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