February 3, 2016

Cornell Professor Creates First Self-Assembled 3-D Superconductor

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After more than two decades of research, Prof. Ulrich Wiesner, material science and engineering, created the first ever self-assembled, three-dimensional superconductor with a research group of graduate students and professors of different disciplines.

Wiesner’s team published its findings on superconductors, which are materials through which electron energy flows without resistance, in online journal Science Advances Friday.

“Superconductivity is such an intriguing property. Once you have this state, electrons move around without any resistance, which means without losing energy to their environments,” Wiesner said. “Think of how much energy would be saved if all our wires would be made of superconductors. It would be incredible.”

Wiesner said this is the first time a superconductor has self-assembled into a porous, three-dimensional gyroidal structure. After years of collaboration with co-author Prof. Sol Gruner, physics, Wiesner developed the idea for the gyroidal structure, employing niobium nitride as the superconducting material brought the idea to fruition.

“The superconductors have this so-called gyroid nanostructure which provides a network of nanopores of around 15 nanometers that percolates the entire superconducting structure,” Wiesner said. “The width of the superconducting struts separating the pores itself is only of order 10 to 20 nanometers.”

Diverging from the typical bulk material used to create superconductors, Wiesner’s team utilized a self-assembling, synthetic block copolymer assembled in Wiesner’s labs.

“We used the power of self-assembly,” Wiesner said. “What this means is that we harnessed the ability of polymers to spontaneously form specific structures, nanostructures, to direct the structure of a superconductor.”

In doing so, the team connected “two fields [of science] that so far never really connected” — organic molecule self-assembly and low temperature physics, according to Wiesner.

While Wiesner’s team did not have a particular use for the superconductor in mind, the technology could be applied to electromagnets as well as to future, unknown applications.

Wiesner’s achievement also expands possibilities for the future research and creation of superconductors, he said.

“The gyroid structure is only one of many, many spontaneous structures that polymers and other self-assembly systems form,” Wiesner said. “We can now start to test how these structures will change the properties of superconductors.”

The novel nature of the team’s superconductor provides expanded opportunity for experimentation with the effects of nanostructures on superconductors.

“The other feature that we now have is that the superconductors we made have huge internal surface areas as the materials are full of small pores,” he said. “We therefore now can now backfill these pores with a second materials, for example an insulator, a semiconductor, a metal, or another superconductor, and see how that changes the electronic or magnetic properties of the materials,” he said.

Additional potential benefits of the team’s achievements await continued research into how exactly the superconductor functions and why the material requires reheating. The research team is left with even more questions now than when they began the study, according to Wiesner.

“Why did we have to first heat treat, then cool, and then heat treat again to even higher temperatures to see the superconducting state? We don’t know the answer to this question yet,” Wiesner said. “What happens if we change the nanostructure? How will that influence the magnetic and electronic properties? What other superconducting materials can be employed? So far we only used niobium nitride. Are there others that would work as well?”