Chiral selectivity of improper ferroelectricity in single-wallPbTiO3nanotubes

Abstract

Full density functional theory calculations successfully demonstrate that a remarkable spontaneous polarization can stably exist in extremely thin ${\mathrm{PbTiO}}_{3}$ single-wall nanotubes (PTO-SWNTs) folded from (110) nanosheets with a specific chirality of ($m$, 0), whereas ferroelectricity is absent from nanotubes with other chiralities and from the unfolded thin films. In other words, there is chiral selectivity of ferroelectricity. The chirality of the ferroelectric (FE) nanotubes plays a variety of significant roles in (i) the stabilization of a low-energy single-wall tubular structure, (ii) the emergence of antiferrodistortive (AFD) distortion hidden in the ${\mathrm{PbTiO}}_{3}$ bulk, and (iii) the strong coupling between FE and emergent AFD distortions. The direct FE-AFD coupling stabilizes the remarkable FE distortion in these ultrathin nanotubes through tilting of oxygen octahedra, suggesting improper ferroelectricity. The existence of a large spontaneous polarization suggests that PTO-SWNTs hold promise for applications in advanced sensors and nanoscale energy-harvesting devices.