Abstract
The interplay between vibrational modes and Kondo physics is a fundamental aspect of transport properties
of correlated molecular conductors. We present theoretical results for a single molecule in the Kondo regime
connected to left and right metallic leads, creating the usual coupling to a conduction channel with left-right
parity even. A center-of-mass vibrational mode introduces an additional phonon-assisted tunneling through
the antisymmetric odd channel. A non-Fermi-liquid fixed point, reminiscent of the two-channel Kondo effect,
appears at a critical value of the phonon-mediated coupling strength. Our numerical renormalization-group
calculations for this system reveal non-Fermi-liquid behavior at low temperatures over lines of critical points.
Signatures of this strongly correlated state are prominent in the thermodynamic properties and in the linear
conductance.
