  Interaction between light and molecular vibrations leads to hybrid
light-matter states called vibrational polaritons. Even though many intriguing
phenomena have been predicted for single-molecule vibrational strong coupling
(VSC), several studies suggest that these effects tend to be diminished in the
many-molecule regime due to the presence of dark states. Achieving single or
few-molecule vibrational polaritons has been constrained by the need for
fabricating extremely small mode volume infrared cavities. In this work, we
propose an alternative strategy to achieve single-molecule VSC in a
cavity-enhanced Raman spectroscopy (CERS) setup, based on the physics of cavity
optomechanics. We then present a scheme harnessing few-molecule VSC to
thermodynamically couple two reactions, such that a spontaneous electron
transfer can now fuel a thermodynamically uphill reaction that was
non-spontaneous outside the cavity.
