SSCU Seminar
Name: Prof. Krishna Reddy Nandipati
Affiliation: Department of Chemistry, IIT Madras
Title: Cavity QED with Highly Symmetrical Molecules
Date & Time: Friday, 24th April 2026 at 04.00 p.m.
Venue: RBM Lecture Hall, Chemical Sciences Building
Abstract:
Molecular polaritons resulting from symmetric organic molecules and cavity systems are a recent focus of study in cavity-assisted control of chemistry [1-3] and quantum computing technologies [1-2, 4]. Highly symmetric molecular systems (i.e. with C3 symmetry axis or higher), such as benzene and sym-triazine, at their equilibrium geometries possess manifold of doubly-degenerate (E) electronic ex-cited states that feature finite angular momentum. By symmetry rules, the E states are vibronically cou-pled via vibrational modes of e symmetry through an exchange of angular momenta, leading to the so-called (E × e) Jahn-Teller (JT) effect [5, 6]. In this talk, I will discuss the properties of polaritons that form when such a JT active molecule are coupled to a Fabry-Perot (FP) cavity supporting two orthogonal modes with (+/−)-circular polarizations (cf. Fig. 1). We find that an efficient exchange of angular momentum between the molecular vibronic and cavity photonic degrees of freedom takes place, resulting in polaritonic states with mixed (+/−)-circular polarization [7]. The magnitude of net cavity polarization is thereby suppressed and, remarkably, the direction of the polarization can get inverted in these polaritons. Furthermore, when more than one JT molecule is coupled to the FP cavity, we find that collective effects dramatically alter the interplay of vibronic and photonic angular momenta, giving rise to markedly different polaritonic spectra and dynamics even when going from one to two JT molecules [8]. Specifically, the JT molecules can access a cascade of high-angular-momentum vibronic states in the presence of a single cavity photon, in sharp contrast to the single molecule case where the range of accessible vibronic angular momentum values are bounded. The observable consequences of this “vi-bronic cascade” are a broadening of the polariton spectrum and a further suppression of photon polari-zations generated under broadband excitation, when compared to the single molecule case.
References:
1. B. Xiang and W. Xiong, Chem. Rev. 124, 2512 (2024).
2. R. Bhuyan, J. Mony, O. Kotov, G. W. Castellanos, J. G´omez Rivas, T. O. Shegai, and K. Borjesson, Chem. Rev. 123, 10877 (2023).
3. O. Vendrell, Chem. Phys. 509, 55 (2018).
4. B. Gurlek and D. Wang, Phys. Rev. Res. 7, 021001 (2025).
5. I. Bersuker, The Jahn-Teller effect (Cambridge University Press, 2006
6. K. R. Nandipati and O. Vendrell, Phys. Rev. Research 3, L042003 (2021).
7. K. R. Nandipati and O. Vendrell, Phys. Rev. A. 107, L061101 (2023).
8. S. Pandit, A. Pandey, A. Shankar, K. R. Nandipati, Collective vibronic cascade in cavity-cou-pled Jahn-Teller active molecules (https://arxiv.org/abs/2511.07880).