Fig. 5: Changes of polarization patterns under external electric fields.
From: Observation of multi-order polar radial vortices and their topological transition
a Vertical PFM phase image of the initial domain pattern. b Vertical PFM phase image after writing experiment with a voltage of 40 V. c Vertical PFM phase image after additional writing experiment with opposite voltage of −40 V. The red, green and yellow circles denote three kinds of topological transitions. d Enlarged vertical PFM phase images of one nanostructure highlighting by red circle in (a–c). e Corresponding schematics of (d), suggesting the transition from three-order radial vortex to NTD and finally radial vortex. f Enlarged vertical PFM phase images of one nanostructure highlighting by green circle in (a–c). g Corresponding schematics of (f), suggesting the transition from two-order radial vortex to NTD and finally two-order radial vortex. h Enlarged vertical PFM phase images of one nanostructure highlighting by yellow circle in (a–c). i Corresponding schematics of (h), suggesting the transition from two-order radial vortex to NTD and finally one-order radial vortex. The one-order, two-order and three-order radial vortices are abbreviated to 1-vor., 2-vor. and 3-vor., respectively.
