Collectively-Modified Intermolecular Electron Correlations: The Connection of Polaritonic Chemistry and Spin Glass Physics.

Polaritonic chemistry has garnered increasing attention in recent years due to pioneering experimental results, which show that site- and bond-selective chemistry at room temperature is achievable through strong collective coupling to field fluctuations in optical cavities. Despite these notable experimental strides, the underlying theoretical mechanisms remain unclear. In this focus review, we highlight a fundamental theoretical link between the seemingly unrelated fields of polaritonic chemistry and spin glasses, exploring its profound implications for the theoretical framework of polaritonic chemistry. Specifically, we present a mapping of the dressed many-molecules electronic-structure problem under collective vibrational strong coupling to the analytically solvable spherical Sherrington-Kirkpatrick (SSK) model of a spin glass. This mapping uncovers a collectively induced spin glass phase of the intermolecular electron correlations, which could provide the long sought-after seed for significant local chemical modifications in polaritonic chemistry. Overall, the qualitative predictions made from the SSK solution (e.g., dispersion effects, phase transitions, differently modified bulk and rare event properties, heating, etc.) agree well with available experimental observations. Our connection not only demonstrates the relevance of moving beyond the dilute gas approximation, where the Fermionic nature of the electrons becomes an essential ingredient, but it also paves the way for novel computational strategies to quantify the subtle chemical characteristics of the cavity-induced spin glass phase. Moreover, our mapping provides a versatile framework to incorporate, adapt, and explore a wide range of spin glass concepts within polaritonic chemistry. Ultimately, the connection also offers fresh insights into the applicability of spin glass theory beyond condensed matter systems suggesting novel theoretical directions such as spin glasses with explicitly time-dependent (random) interactions.