Topological phase transition in polar skyrmions: a perspective from second principles simulations

When ultrathin ferroelectric layers of PbTiO₃ are embedded in superlattices with SrTiO₃, the interplay between elastic, electrostatic, and gradient energies produces complex patterns of the electrical polarization. In particular, depending on the mechanical boundary conditions, nanometer scale of vortex arrays¹ and topologically non-trivial polar skyrmion bubbles have been recently detected². Using second-principles methods³ as implemented in the SCALE-UP code⁴ we study the response of these topologically protected structures to electric field and temperature. We show a reversible phase transition from the skyrmion state to a trivial uniform ferroelectric state, accompanied by large tunability of the dielectric permittivity⁵.

¹ A. K. Yadav et al., Nature 530, 198 (2016)
² S. Das et al., Nature 568, 368 (2019)
³ J. Wojdel et al., J. Phys.:Condens. Matter 25, 305401 (2013)
⁴ P. García-Fernández et al., Phys. Rev. B 93 195137 (2016)
⁵ S. Das et al., Nat. Mater. (2020)