The ferroelectricity of group-IV chalcogenides $MX$ ($M$=Ge, Sn; $X$=Se, S) monolayers has been extensively investigated, but 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 as increasing the number of intermediate steps and converges to a value that is almost independent of the tube diameter.

The organic molecules in hybrid perovskites can easily rotate within the inorganic lattice at room temperature, leading to a crystal-liquid duality. The liquid-like behavior of the organic molecules is commonly...

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