  It was recently shown [G. Albareda, et al., Phys. Rev. Lett. 113, 083003
(2014)] that within the conditional decomposition approach to the coupled
electron-nuclear dynamics, the electron-nuclear wave function can be exactly
decomposed into an ensemble of nuclear wavepackets effectively governed by
nuclear conditional time-dependent potential-energy surfaces (C-TDPESs).
Employing a one-dimensional model system we show that for strong nonadiabatic
couplings the nuclear C-TDPESs exhibit steps that bridge piecewise adiabatic
Born-Oppenheimer PESs. The nature of these steps is identified as an effect of
electron-nuclear correlation. Furthermore, a direct comparison with similar
discontinuities recently reported in the context of the exact factorization
framework allows us to draw conclusions about the universality of these
discontinuities, viz. they are inherent to all nonadiabatic nuclear dynamics
approaches based on (exact) time-dependent potential energy surfaces.
