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Controlling Topological Effects in Magnetic Systems
The importance of topology in condensed matter physics has expanded in recent years as it has become a key piece of understanding the physics in various phenomena. In this thesis, we examine several examples of the power of topological concepts in defining and understanding certain systems and effects. We consider magnetic skyrmions, whirls of magnetic texture, the topology of which is signified by the topological charge, a quantity dependent on the configuration of the magnetic moments in real space. The stability granted by this topology makes skyrmions of interest for computing applications. For elongated skyrmions coupled to a superconductor, the existence of an energy gap can indicate that the region around the skyrmion is in a topological phase. This makes it possible for Majorana bound states to exist at the edges of the skyrmion. Majorana bound states provide great promise for quantum computing, as they behave as non-abelian anyons. We also study Berry curvature, for both electrons and magnons in momentum space, which leads to various versions of the Hall effect in both cases. These Hall effects, which can give rise to transverse currents, including charge and spin currents, could also be used for devices. In the electron case, we show how in a system of graphene atop a chromia substrate, the Chern number represents the topological nature of the system and signifies which effects will be present, such as the quantum anomalous Hall effect and valley-polarized quantum anomalous Hall effect. For an insulating noncollinear antiferromagnet, we calculate the magnon spin Nernst response for potassium iron jarosite KFe3(OH)6(SO4)2.
Physics|Computer science|Condensed matter physics
Sandhoefner, Shane, "Controlling Topological Effects in Magnetic Systems" (2021). ETD collection for University of Nebraska - Lincoln. AAI28489756.