In the simplest molecues, diatomic molecules made form two atoms, the vibration and rotation degrees of freedom gives rise to new features such as strong long-range dipolar interactions between molecules, a key ingredient in many quantum simulation and quantum computing proposals.
Polyatomic molecules are an exciting new research frontier, as these molecules offer an even richer internal structure useful for many applications. In the past year, we have investigated some aspects of the triatomic molecule SrOH both theoretically and experimentally. Experimentally, we have demonstrated coherent bichromatic force deflection of molecule by making use of two lasers beams with precisely tuned frequencies and phases. Our demonstration of the bichromatic force opens the door to efficient optical deceleration of diatomic and polyatomic molecules with complex level structures, potentially providing access to ultracold samples of a much larger class of molecules.
On the theoretical front, we have investigated using SrOH as a probe for ultralight dark matter. We have found that SrOH is exquisitely sensitive to variation in the proton-to-electron mass ratio, thanks to near-degeneracy of vibrational modes of different character. Time variation of the proton-to-electron has not been observed in experiments, but has been theoretically proposed as one of the consequences of ultra-light dark matter particles. Our work demonstrates that triatomic molecules, and more generally polyatomic molecules, can provide greatly enhanced sensitivities in dark matter searches, and in general, searches for variation of fundamental constants.