  Kinetics of conformational change of a semiflexible polymer under mechanical
external field were investigated with Langevin dynamics simulations. It is
found that a semiflexible polymer exhibits large hysteresis in mechanical
folding/unfolding cycle even with a slow operation, whereas in a flexible
polymer, the hysteresis almost disappears at a sufficiently slow operation.
This suggests that the essential features of the structural transition of a
semiflexible polymer should be interpreted at least on a two-dimensional phase
space. The appearance of such large hysteresis is discussed in relation to
different pathways in the loading and unloading processes. By using a minimal
two-variable model, the hysteresis loop is described in terms of different
pathways on the transition between two stable states.
