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Colloquium | Materials Science Colloquium | Materials Science Division

Axisymmetric Two-Dimensional Solitons

Materials Science Colloquium

Abstract: The electric field experienced by a traveling electron translates, in its rest frame, to a magnetic field proportional to its velocity — a relativistic effect that is notable in crystalline lattices with heavy atoms. The Zeeman interaction between the electron spin and this effective magnetic field is equivalent to the coupling of the electronic spin and momentum degrees of freedom, known as spin-orbit coupling (SOC). Importantly, SOC effects are greatly enhanced in reduced dimensions: inversion symmetry is broken at the surface or interface, and the resultant electric field couples to the spin of itinerant electrons. The states induced by engineering SOC and inversion symmetry breaking in magnetic materials open a broad perspective, with impact in the technology of spin topology. For example, in conventional ferromagnets the exchange interaction aligns spins and the anisotropy determines energetically preferred orientations. Meanwhile, the interaction generated by SOC and broken inversion symmetry induces a relative tilt between neighboring spins. Axisymmetric two-dimensional solitons form due to the competition between these winding” and aligning” exchange interactions. These nanometer-scale localized objects are being proposed as candidates for novel technological applications, including high-density memory, logic circuits and neuro-inspired computing. Using a novel materials architecture, I will address quantifiable insights toward understanding their stability and dynamics, and directions for exploiting their properties in nanoscale devices.

Bio: I received my Ph.D. from the University of Cambridge (Trinity College). I am currently a professor of physics and applied physics and the inaugural Research Professor of Physics at the Nanyang Technological University – Singapore.

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