Blackbody radiation and thermal effects on chemical reactions and phase transitions in cavities

An important question in polariton chemistry is whether reacting molecules are in thermal equilibrium with their surroundings. If not, can experimental changes observed in reaction rates of molecules in a cavity (even without optical pumping) be attributed to a higher/lower temperature inside the cavity? In this work, we address this question by computing temperature differences between reacting molecules inside a cavity and the air outside. We find this temperature difference to be negligible for most reactions [1]. On the other hand, for phase transitions inside cavities, as the temperature of the material is actively maintained by a heating/cooling source in experiments, the phase transition temperature can be modified as shown in recent experiments [2-3]. In our work, we show that cavities can modify observed transition temperatures when mirrors and cavity windows are ideal (non-absorbing); however, this modification vanishes when real mirrors and windows are used and the entire polariton system is taken to be at the same temperature. This conclusion relies on having low contact resistance between mirrors and molecules. We expect this modification to reappear if there is a temperature gradient between the photonic and material components of the polariton system.

[1] S. Pannir-Sivajothi and J. Yuen-Zhou, "Blackbody radiation and thermal effects on chemical reactions and phase transitions in cavities," arXiv:2402.01043 (2024)

[2] Z. Brawley†, S. Pannir-Sivajothi†, J. E. Yim†, Y. R. Poh, J. Yuen-Zhou, and M. Sheldon, "Vibrational weak and strong coupling modify a chemical reaction via cavity-mediated radiative energy transfer," ChemRxiv preprint (2023)

[3] G. Jarc, S. Y. Mathengattil, A. Montanaro, F. Giusti, E. M. Rigoni, R. Sergo, F. Fassioli, S. Winnerl, S. Dal Zilio, D. Mihailovic et al., “Cavity-mediated thermal control of metal-to-insulator transition in 1T − TaS2,” Nature 622, 487–492 (2023)