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A Graphene Superconductor Stronger Than Any Other Substance

Researchers at the U.S. Department of Power’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a graphene device that’s thinner than a human hair but has a depth of unique traits. It quickly switches from a superconducting material that conducts electricity without losing any energy to an insulator that resists the circulate of electric current, and back again to a superconductor – all with a simple flip of a change. Their findings reported at the moment in the journal Nature.

The graphene device is composed of three atomically thin (2D) layers of graphene. When sandwiched between 2D layers of boron nitride, it forms a repeating pattern referred to as a moiré superlattice. The material might help other scientists understand the complicated mechanics behind a phenomenon known as high-temperature superconductivity, where a document can conduct electricity without resistance at temperatures higher than expected, though still hundreds of degrees below freezing.

In a previous study, the researchers reported observing the properties of a Mott insulator in a device made of trilayer graphene. A Mott insulator is a class of material that somehow stops conducting electricity at hundreds of levels beneath freezing despite classical theory predicting electrical conductivity. But it has long been believed that a Mott insulator can become superconductive by including extra electrons or positive charges to make it superconductive, Chen explained.

For the last one decade, researchers have been studying ways to combine different 2D materials, often starting with graphene – a material known for its capacity to conduct heat and electricity efficiently. Out of this body of work, other researchers had discovered that moiré superlattices formed with graphene exhibit exotic physics corresponding to superconductivity when the layers are aligned at just the right angle.

Chen said that “So for this study, they asked ourselves, ‘If our trilayer graphene system is a Mott insulator, could it also be a superconductor?’

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