Molecular Polaritonics
Optical cavities confine electromagnetic fields that can couple strongly to molecular vibrations, forming hybrid light–matter states called polaritons. Dr. Hasyim studies how this coupling changes molecular motion, from individual reaction events to the slow structural relaxation of a liquid. His work combines quantum-dynamical benchmarks with molecular simulations to connect the underlying interactions to changes in reactivity and energy flow.
Non-Thermal Aging of Supercooled Liquids in Optical Cavities
Accepted in Nature Communications · Preprint · Simulation code
A liquid’s vibrations respond to an optical cavity much faster than its molecular structure can rearrange. Dr. Hasyim, Arianna Damiani, and Norah Hoffmann used this separation of timescales to investigate whether cavity coupling could control the aging of a model supercooled liquid. In their simulations, switching on the coupling redistributed energy between fast vibrations and slow intermolecular motion while the bath temperature remained fixed. Structural relaxation slowed and acquired a dependence on the time elapsed since activation of the coupling, a characteristic of aging. The structure also reached energies associated with a colder equilibrium liquid, described by a lower structural fictive temperature. This provides a way to distinguish structural changes from the temperature of molecular motion. [1]
Building on this result, the team developed cavity configurational feedback cooling. The protocol cycles the cavity coupling and adjusts the bath temperature to follow the inferred structural temperature, limiting reheating from the surroundings. Simulations showed progressively lower structural temperatures under this combined coupling-and-bath protocol. Here, the bath temperature changes during the feedback cycle, whereas the initial aging calculation holds it fixed. The two calculations connect a transient redistribution of molecular energy to a strategy for controlling slow structural evolution. Together, they motivate further study of how field protocols and thermal environments influence the stability of disordered materials.
Toward Accurate Mixed Quantum Classical Simulations of Vibrational Polaritonic Chemistry
Published in The Journal of Chemical Physics 164, 094116 (2026) · Journal · Preprint
Predicting cavity-modified reactions requires a reliable treatment of quantum dynamics before extending simulations to many molecules. Dr. Hasyim, Arkajit Mandal, and David Reichman tested mixed quantum-classical methods against a fully quantum reference for a single-molecule reaction model. To this end, they applied the mapping approach to surface hopping (MASH) and compared classical and quantum descriptions of the cavity mode. Among the tested approximations, MASH with a quantum cavity mode gave the most accurate reaction-rate profile. The comparison establishes the importance of both the dynamics method and the treatment of the confined field for this benchmark. [2]
However, the tests also exposed a limiting-case error in multistate MASH. Even when the molecule and cavity were uncoupled, adding quantum cavity states could change the predicted long-time dynamics through unphysical transitions. Dr. Hasyim and collaborators introduced ε-MASH to suppress hops between states with negligible nonadiabatic coupling, addressing this size-inconsistency problem. The work therefore supplies both a benchmark for cavity-modified rates and a correction to the dynamics algorithm. Extending these methods to collective systems remains a research direction, supported by the single-molecule tests reported in this paper.