Universal Steps in Quantum Dynamics with Time-Dependent Potential-Energy Surfaces: Beyond the Born-Oppenheimer Picture

TL;DR

This paper demonstrates that nonadiabatic nuclear dynamics universally involve step-like features in potential-energy surfaces, arising from electron-nuclear correlation, across different theoretical frameworks.

Contribution

It reveals the universal presence of step features in time-dependent potential-energy surfaces during nonadiabatic dynamics, beyond the Born-Oppenheimer approximation.

Findings

Nuclear C-TDPESs show steps bridging adiabatic PESs under strong nonadiabatic couplings.

Steps are caused by electron-nuclear correlation effects.

Discontinuities are universal in all exact time-dependent potential energy surface approaches.

Abstract

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.