An international team led by University of Toronto physicists has developed a simple new technique using Scotch poster tape that has enabled them to induce high-temperature superconductivity in a semiconductor for the first time.
"Who would have thought simply sticking things together can generate entirely new effects?" said team leader and U of T physicist Ken Burch (shown). High-temperature superconductors are materials that conduct electricity without heating up and losing energy at liquid nitrogen temperatures. They are currently in use for transmitting electricity with low loss and as the building blocks of the next generation of devices (i.e., quantum computers).
However, only certain compounds of iron, copper and oxygen – or cuprates – have shown high-temperature superconducting properties. Cuprates were believed to be impossible to incorporate with semiconductors, and so their real-world 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 semiconductor – has been difficult because the fundamental quantum mechanics require the materials to be in nearly perfect contact.
That’s where the poster tape comes in. "Typically, junctions between semiconductors 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."
So instead, the team used Scotch poster tape and glass slides to place high-temperature superconductors in proximity with a special type of semiconductor known as a topological insulator. Topological insulators have captured world-ide attention from scientists because they behave like semiconductors in the bulk, but are very metallic at the surface. The result was induced superconductivity in these novel semiconductors: a physics first, according to Burch.
The U of T team members include Kenneth S. Burch, Alex Hayat, Parisa Zareapour, Shu Yang F. Zhao, Michael Kreshchuk, Achint Jain. All are members of the Department of Physics and Institute for Optical Sciences and Alex Hayat who 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 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.
Caption: University of Toronto physics professor Ken Burch with experimental apparatus and tape.