  Current-induced bond rupture is a fundamental process in nanoelectronic
architectures such as molecular junctions and in scanning tunneling microscopy
measurements of molecules at surfaces. The understanding of the underlying
mechanisms is important for the design of molecular junctions that are stable
at higher bias voltages and is a prerequisite for further developments in the
field of current-induced chemistry. In this work, we analyse the mechanisms of
current-induced bond rupture employing a recently developed method, which
combines the hierarchical equations of motion approach in twin space with the
matrix product state formalism, and allows accurate, fully quantum mechanical
simulations of the complex bond rupture dynamics. Extending previous work [J.
Chem. Phys. 154, 234702 (2021)], we consider specifically the effect of
multiple electronic states and multiple vibrational modes. The results obtained
for a series of models of increasing complexity show the importance of vibronic
coupling between different electronic states of the charged molecule, which can
enhance the dissociation rate at low bias voltages profoundly.
