Scientists induce superconductivity in graphene by applying 10,000 atmospheres pressure

Superconducting properties achieved by applying pressure of more than 10,000 atmospheres on a bilayer graphene sample

Scientists at Columbia University have found a new way to induce superconductivity in twisted bilayer graphene. Fine-tuning adjacent layers of graphene by applying pressure helps turns this two-dimensional material into a superconductor, they claim.

Graphene has been described as a wonder material, thanks to a multitude of its amazing properties. At one atom thick, it is the thinnest material known to date. At the same time, it is the strongest material known, about 200 times stronger than steel. It is an excellent conductor of heat and electricity, and a material with unlimited potential for application in almost any industry.

Graphene also has a great potential to be a superconducting material. The flat, hexagonal lattice structure of graphene offers relatively little resistance to electrons, allowing electrical conduction better than even good conductors like copper and almost as well as superconductors.

In an earlier study published in March last year, a team of researchers at the Massachusetts Institute of Technology claimed to have found a new method to induce superconductivity in graphene. The researchers said a bilayer graphene sample demonstrates superconducting properties when twisted at an angle of 1.1 degrees, referred to as the "magic angle."

However, twisting the layers to such an angle is extremely challenging.

"The layers must be twisted to within roughly a tenth of a degree around 1.1, which is experimentally challenging," says Cory Dean, assistant professor of physics at Columbia University and the lead researchers of the current study.

"We found that very small errors in alignment could give entirely different results."

Realising that precisely controlling the angle is extreme difficult, Dean's team - which included researchers from the University of California, Santa Barbara, and the National Institute for Materials Science - decided to alter the space between two layers. Researchers believed that would change the twist angle into a magic angle.

The researchers took a graphene sample with a twist angle of 1.3 degrees and applied pressure of over 10,000 atmosphere, which led to emergence of superconducting as well as insulating phases in the sample. The superconductivity was found to develop at the just over 3 degrees above absolute zero.

The researchers believe the critical temperature of the superconductivity may be further increased at even higher pressures.

The team is now experimenting with other atomically-thin, two-dimensional materials in the hope to discover superconducting properties in some of these systems.

"Understanding 'why' any of this is happening is a formidable challenge but critical for eventually harnessing the power of this material—and our work starts unravelling the mystery,'" Dean said.

The findings of the study are published in journal Science.