  A current was injected into a single MoS2 nanotube using an
atomic-force-microscopy probe. The trapped electrons and holes caused a partial
collapse of the nanotube and its helical twisting. The topography changes can
be explained by the reverse piezoelectric effect, the theory of which was
proposed for chiral nanostructures. Work-function modifications were observed,
which were dependent on the polarity of the injected carriers.
