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Donuts, superconductors and green electronics – a physics professor explains their connection

by Julia Renner, Marine Biology, 2018

If you’ve ever wondered what superconductors, donuts, and green electronics have in common, then you’re unusually imaginative — but the answer comes in the form of a paper recently published in Nature by Don Heiman, Professor of Physics at Northeastern University, who participated in work making topological insulators more feasible for use in everything from iPhones to quantum computing.

As well as a professor, Heiman is a fellow of the American Physical Society and the director of the Nanomaterials Instrument Facility. He explains what makes topological insulators unique by comparing them to a glazed donut. “It’s as if, when you sliced the donut open, there was still glaze on the new surfaces,” he explains. In the context of the topological insulators Heiman worked with, this simply means that when the ‘donut’ of the insulator is sliced, the new surfaces become conducting. ‘Topological’ refers to this effect on the surface; ‘insulator’ to the material not being electrically conducting.

Heiman and collaborators took a new approach to magnetizing topological insulators, a goal that’s been pursued for some time now. They put thin layers of the insulator together with thin layers of a ferromagnet. This produces a conducting material that produces much less scattering of electrons when used, producing a phenomenon known as the Quantum Anomalous Hall Effect. The reduction in electron scatter results in what’s called a dissipationless current, essentially producing a superconductor-like material — a highly efficient conducing material that experiences very little resistance and can therefore function with much less power and on far less energy. This has implications, Heiman explains, for a wide range of electronics. Phones, for instance, could become able to function for a much longer time, making them more efficient and greener. On the other end of the spectrum, quantum computers will need these kinds of conductors because they rely on quantum entanglement — meaning that materials like these magnetized topological insulators are useful because of the unique ways in which their electrons behave.

Until now, however, a major obstacle has been the fact that this superconducting-like effect can function only at extremely low temperatures, making them impractical for widespread use or for electronics that heat up while functioning. What makes Heiman and collaborators’ work exceptional is that they were able to magnetize the topological insulators’ surfaces at temperatures far higher than they could be previously. By layering the insulator and ferromagnetic materials in this new way, they open up a wide range of possibilities for future applications.

There is still the potential for research into understanding exactly how and why this new method would allow the Quantum Anomalous Hall Effect to occur at higher temperatures, and plenty of room to further the work. “Further increasing the operating temperature to room temperature,” Heiman explains, could “greatly reduce the energy consumption of electronics and the Internet,” and “realize next-generation electronics.”

Physics professor Don Heiman in an archive photo

Physics professor Don Heiman in an archive photo

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