Scientists have been working on creating electronic devices with little or no resistance to electricity in an effort to reduce heat output, save energy and extend device capabilities. Over the past few years, theorists and experimentalists have been trying to achieve this goal using extremely thin materials with special physical properties, called topological insulators (TIs). Cui-Zu Chang was at the forefront of a recent breakthrough in this technology.
TIs allow the free flow of electrons only on their surface while blocking the flow of electrons through their bulk. MIT postdoc Cui-Za Chang and his colleagues at Tsingshua and Stanford Universities reported the experimental demonstration of electrons flowing only along the edge of a topological insulator film circuit, driven by an internal magnetic field (referred to as the quantum anomalous Hall effect).
To provide internal magnetism for their circuit, the scientists added chromium to their material, which was composed of bismuth, antimony, and tellurium. However, the experiment still showed remnants of electrical resistance to the edge current, close to zero resistance.
Using local and nonlocal measurements, Chang and colleagues at MIT and Penn State University were later able to achieve zero resistance to current flowing lengthwise along the edge of their sample circuit at the low temperature of 25 milikelvins (or 0.025 kelvins). Additionally, Chang’s research suggests that a vanadium system (as opposed to a purely chromium system) shows magnetism at below 23 kelvins, which makes it superior for observing the quantum anomalous Hall effect.
“A signal entering this system can propagate a long distance without losing any of its energy. While presently it can only be realised at very low temperatures, there are indications that this can be raised,” Chang said in a comment to MIT news.
“If you can realise this effect at room temperature, it will significantly change our life. You can use this kind of effect to develop quantum electronics including the quantum computer.
“In this kind of computer, there is minimal heating effect; the current flow is completely dissipationless; and you can also communicate over very long distance.”
Image source: MIT news