U of T's Ken Burch of the Department of Physics and Institute for Optical Sciences (Photo by Diana Tyszko)

A first for physics: inducing superconductivity in a semi-conductor with Scotch Tape

An international team led by University of Toronto physicists has developed a simple new technique to induce high-temperature superconductivity in a semiconductor for the first time - using Scotch Tape.

The method paves the way for new devices that could be used in quantum computing and to improve energy efficiency.

“Who would have thought simply sticking things together can generate entirely new effects?” said team leader and U of T physicist Ken Burch.

High-temperature superconductors are materials that conduct electricity without heating up or  losing energy at liquid nitrogen temperatures. Used to transmit electricity with low loss, these superconductors are also the building blocks of the next generation of devices such as quantum computers. 

However, only certain compounds of iron, copper and oxygen – or cuprates – reveal high-temperature superconducting properties. Cuprates were believed to be impossible to incorporate with semi-conductors, so their use has been severely limited as has the exploration of new effects they may generate. 

For example, observing the phenomenon of the proximity effect – wherein the superconductivity in one material generates superconductivity in an otherwise normal semi-conductor – has been difficult because the fundamental quantum mechanics require the materials to be in nearly perfect contact.

That’s where the tape comes in – specifically, Scotch poster tape: a thin, two-sided version of Scotch Tape.

“Typically, junctions between semi-conductors and superconductors were made by complex material growth procedures and fabricating devices with features smaller than a human hair,” explains Burch. “However the cuprates have a completely different structure and complex chemical make-up that simply can’t be incorporated with a normal semiconductor.”

The team used Scotch poster tape and glass slides to place high-temperature superconductors in proximity with a special type of semi-conductor known as a topological insulator.  Topological insulators have captured world-wide attention from scientists because they behave like semi-conductors in bulk, but are very metallic at the surface.  

The result - induced superconductivity in these novel semi-conductors - was a physics first.

In addition to Burch, the U of T team included Alex Hayat, Parisa Zareapour, Shu Yang F. Zhao, Michael KreshchukAchint Jain.  All are members of the Department of Physics and Institute for Optical Sciences and Hayat holds an additional appointment with U of T’s Centre for Quantum Information and Quantum Control.

Other scientists collaborating on the project are: Sang-Wook Cheong, Daniel C. Kwok and Nara Lee of Rutgers University,  G.D. Gu,  Ahijun Xu and Zhijun Xu of Brookhaven National Laboratory and Robert Cava of Princeton.

The team's findings are published in Nature Communications, an online-only journal. The online version of the article can be considered definitive. These papers will be citable via a digital object identifier (DOI) number. The DOI for this paper is 10.1038/ncomms2042. Once the paper is published electronically, the DOI can be used to retrieve the paper by adding it to the following URL: http://dx.doi.org/

The work was supported by the Natural Sciences and Engineering Research Council of Canada, the Canadian Foundation for Innovation, the Ontario Ministry for Innovation and the National Science Foundation.

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