Video of the week: Upside-down ‘levitation’ of superconducting puckPublished on October 31st, 2011 | By: Eileen De Guire
The phenomenon of superconductivity was discovered in 1911. Fifty years of physics research followed, and in 1962 Westinghouse introduced the first commercial superconducting wire, a niobium-titanium alloy wire. Its critical temperature is in the 10 K range, and, to reach those temperatures, liquid helium is used as a coolant.
The next big breakthrough occurred in the mid-1980s with the discovery of so-called high-temperature conductivity in certain copper oxide-based compounds, where the critical temperatures are above 77 K. With critical temperatures that high, cheaper and easier-to-use liquid nitrogen can be used as the coolant. Cuprate superconducting compositions have critical temperatures that range from 92 K to 134 K.
It was an exciting discovery. Suddenly, there was talk of infrastructure-scale applications, like levitated light rail and electric power delivery. In the intervening 25 years, a lot more physics research has been done to understand the mechanisms of superconductivity, as well as materials science research to understand how it can be optimized and used.
This video is a very cool demonstration of levitation and shows several ways a superconducting puck can be manipulated through the mechanism of quantum locking (also called flux pinning). My grasp of quantum pinning is that magnetic flux lines, which normally permeate in parallel through a material, are guided instead through the crystallographic dislocations, which “pins” the flux lines to certain points. The pinned points of the puck couple with the magnetic track sort of like an invisible strut that locks the puck to the track. The trailing stream of evaporating liquid nitrogen gives the puck an ethereal, fantastical quality.
The material is not specified, but it’s presumed to be a ceramic cuprate composition. It was done by the Superconductivity Group at Tel-Aviv University and is provided via the Association of Science-Technology Centers. A longer video with more explanations of the physics can be viewed here.
Hat tip: Kent Anderson at The Scholarly Kitchen.
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