The semi-rigid rotor is of fundamental and technological significance, e.g., for understanding the unexpected instability of the Explorer I satellite launched in 1958. Molecules are another example of semi-rigid rotors that, unlike satellites, exhibit perfect symmetries. Their free rotations are dictated by quantum permutation statistics and rotational axis tunnelling/superposition. Infrared spectroscopy probes these emergent quantum dynamics driven by rotation-vibration interactions.

In this talk I will cover progress on infrared spectroscopy of more and more complex molecules [1], culminating in the resolved rotational spectrum of an unprecedentedly large and symmetric molecule: C₆₀ [2]. Building upon this work, we discovered that C₆₀ exhibits a new type of ergodicity breaking--an inability to thermalize--that "turns on" and "off" as the molecule spins faster and faster. Moreover, the ergodicity breaking occurs without breaking symmetry [3]. These insights may be relevant to protecting quantum coherence in complex systems, engineering useful quantum materials, and probing matter out of equilibrium, inspired by the dynamics of semi-rigid rotors.

1. Ben Spaun, P. Bryan Changala, David Patterson, Bryce J. Bjork, Oliver H. Heckl, John M. Doyle, and Jun Ye. Nature 533, 517–520 (2016)
2. P. Bryan Changala , Marissa L. Weichman, Kevin F. Lee, Martin E. Fermann, and Jun Ye. Science 363, 49-54 (2019)
3. Lee R. Liu, Dina Rosenberg, P. Bryan Changala, Philip J. D. Crowley, David J. Nesbitt, Norman Y. Yao, Timur V. Tscherbul, and Jun Ye. Science 381, 778-783 (2023)

PLEASE NOTE NON STANDARD LOCATION.