CAREER: Skyrmion-Vortex Interactions in Ferromagnet-Superconductor Heterostructures

Non-technical abstract: The field of spintronics is a rapidly advancing and disruptive research area, producing novel device schemes that are superior to conventional computing electronics. Conventional electronic elements use electron charge to store and transmit information. For example, the amount of charge accumulated on a capacitor may determine whether it contributes a “0” or a “1” binary digit. On the other hand, spintronic devices exploit another property of electrons, called spin (up, down, or canted), to encode information. These devices can in fact use spin currents to control logic operations faster and more energy efficiently than charge currents can accomplish in conventional semiconductor transistor-based logic. Spintronics devices typically consist of ferromagnets as the source of the spin current. Incorporating elements that are superconductors, which have no electrical resistance, can enhance the overall device performance and offer new functionalities, such as remarkably low-dissipation (energy loss) spin transport. Such ferromagnetic-superconductor structures are also constituents of schemes for topological quantum computing, an architecture that is predicted to be robust to environmental noise that plagues other quantum device platforms. This project investigates ferromagnetic-superconductor devices that could form building blocks of novel computing architectures by imaging nanoscale magnetic fields throughout the device and determining the effects of temperature and an applied current on the device operation. This effort also contributes to the development of a globally competitive quantum workforce in the U.S. by designing a novel lab course that teaches foundational skills for careers in quantum sensing and computing, and providing training in electronics to K-12 students at a local elementary school. Technical abstract: Ferromagnet-superconductor (FS) heterostructures are promising platforms for superconducting spintronics and topological quantum computing. In FS heterostructures, it is theoretically predicted that skyrmion-vortex pairs can form that are desirable for computing applications. The objective of this program is to design, fabricate, and study a system in which skyrmions and vortices co-exist and interact. Specifically, the research team studies proximity coupling in two different FS heterostructures: iron germanium telluride (FGT) - superconductor bilayers and arrays of FeGe islands under a superconducting layer. For both heterostructures, they employ magnetic force microscopy and electrical transport measurements to study the dynamics of magnetic textures that emerge in these devices under variable temperatures (down to 1.6 K) and magnetic fields (up to 12 T), determining the conditions under which skyrmions and vortices co-exist and bind. Proposed work includes studies of the effects of thermal energy and current-induced forces, and comparing the results to semiclassical theories describing skyrmion-vortex pair dynamics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.