  Attractive electron correlations due to an electron-vibron interaction (EVI)
can overcome the direct Coulomb repulsion of polarons in strongly deformable
molecular quantum dots (MQDs). If it realizes, a switching appears in the I-V
characteristics of the degenerate nonadiabatic molecular bridges weakly coupled
to electrodes providing a route to ultrafast `memristors' (memory-resistors) as
the basis for future oscillators, amplifers, and other important circuit
elements. Here, we extend our theory of polaronic memristors to adiabatic MQDs
strongly coupled to the leads and show that the degeneracy of MQD (or other
multilevel energy structure) along with the polaron-polaron attraction is a
necessary ingredient of its switching behavior in the strong-coupling regime as
well.

Mesoscale and Nanoscale Physics