Nonmagnetic antiskyrmions expected in barium titanate

02.07.2024 13:00 – 14:30

The prediction and experimental confirmation of magnetic skyrmions - the objects with nontrivial swirling spins patterns - revolutionized the physics of nanoscale magnetism and opened new horizons for spintronics. Despite the inherently shorter and faster correlations of the electric polarization, it seems that the nanoscale ferroelectric research inspired by the magnetics skyrmionics may deserve a further attention.
In this talk I would like to illustrate the above statement by reporting a spontaneous formation of a peculiar topological defect, spotted in an atomistic shell-model computer experiment, originally aimed to study instead the analogue of the bulk Bloch-like skyrmion in a classical ferroelectric perovskite – barium titanate crystal [1]. This accidentally spotted antiskyrmion is nothing more than a tiny, few-nm wide polar column surrounded by a unique noncollinear polarization pattern. However, we show that it has a hexagonal cross-section, and that it carries a very exotic topological charge of minus two. We will explain the meaning of its negative topological charge as well as the mechanism of its formation and stability. We will also argue that this beautiful and unique noncollinear polarization pattern, that has never been described before, arises due to a fortunate combination of the moderate anisotropy of the anharmonic electric susceptibility and the characteristic anisotropy of the polarization correlations in barium titanate crystals. We will indicate which other ferroelectric materials might host such an antiskyrmion and which ones cannot. We shall discuss the impact of antiskyrmion on various crystal properties, try to illustrate possibilities of its motion, and we will also explore the prospects of its experimental evidence that is lacking so far.

Lieu

Bâtiment: Ecole de Physique

auditoire Stuckelberg

entrée libre