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Ferroelectric Control of Topological Properties of Two-Dimensional Materials

Thesis Defense

10:00 am – 12:00 pm
Jorgensen Hall Room: JH 207
Virtual Location: Zoom
Target Audiences:
Physics Department, (402) 472-2770,
Kai Huang will present his thesis topic, “Ferroelectric Control of Topological Properties of Two-Dimensional Materials” in person and via Zoom.

Abstract: Topological characteristics, such as magnetic quasiparticles like skyrmions, have significantly propelled the field of spintronics. The recent discovery of two-dimensional (2D) ferroic materials opens up a novel platform for incorporating these properties within atomic-thin layers, offering potential advancements in the creation of compact spintronic devices. This dissertation focuses on the exploration of topological features of 2D van der Waals (vdW) materials, such as magnetic skyrmions and antiskyrmions, through first-principles density functional theory calculations.
The formation of magnetic skyrmions in 2D vdW ferromagnet Fe3GeTe2 driven by proximity of 2D ferroelectric In2Se3 is studied. The interfacial symmetry breaking produces a sizable Dzyaloshinskii-Moriya interaction (DMI) in a Fe3GeTe2/In2Se3 vdW heterostructure. The magnitude of DMI can be controlled by ferroelectric polarization reversal, leading to creation and annihilation of skyrmions. Additionally, the sign of DMI in a In2Se3/Fe3GeTe2/In2Se3 heterostructure changes with ferroelectric switching, thereby reversing the chirality of the skyrmions.
The emergence of an anisotropic DMI and formation of magnetic antiskyrmions in a vdW assembled 2D magnet CrI3 is studied. Polar layer stacking of two monolayers of CrI3 efficiently lowers the symmetry, resulting in the anisotropic DMI. The DMI is reversible by switching the ferroelectric polarization inherited from the polar layer stacking, offering the control of antiskyrmions by an electric field. Spin-dynamics simulations of a Mn doped CrI3 bilayer with reduced magnetocrystalline anisotropy demonstrate the formation of antiskyrmions and the switching of their spin texture with ferroelectric polarization reversal.
These findings show that the proximity of 2D ferroelectrics and polar layer stacking of 2D vdW ferromagnets can be used as viable techniques for producing magnetic topological quasiparticles and highlight the electrical control of magnetic topological quasiparticles as a promising approach for spintronic devices.

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This event originated in Physics.