Competition between Stepwise Polarization Switching and Chirality Coupling in Ferroelectric GeS Nanotubes

Ferroelectricity of group-IV chalcogenides MX ( M = Ge, Sn; X = Se, S) monolayers has been extensively investigated. However, how the ferroelectricity evolves in their one-dimensional nanotubes remains largely unclear. Employing an accurate deep-learning interatomic potential of first-principles precision, we uncover a general stepwise mechanism for polarization switching in zigzag and chiral GeS nanotubes, which has an energy barrier that is substantially lower than the one associated with the conventional one-step switching mechanism. The switching barrier (per atom) gradually decreases with increasing the number of intermediate steps and converges to a value that is almost independent of the tube diameter. In the chiral GeS nanotubes, the switching path of polarization with chirality coupling is preferred at less intermediate steps. This study unveils novel ferroelectric switching behaviors in one-dimensional nanotubes, which is critical to coupling ferroelectricity and chirality.