High temperature superconductivity in B-doped Q-carbon

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A novel, boron-doped Q-carbon material is said to significantly increase the temperature at which carbon-based materials act as superconductors, according to researchers at North Carolina State University. According to the team, the breakthrough could pave the way for room temperature superconductivity in strongly bonded, light-mass materials.

The previous record for superconductivity in boron-doped diamond was 11Kelvin, whereas the researchers claim the boron-doped Q-carbon has been found superconductive from 37K to 57K.

"B-doped Q-carbon can handle as much as 43million A/cm2 at 21K in the presence of a two Tesla magnetic field,” Professor Jay Narayan explains. “Since we have demonstrated superconductivity at 57K, this means the doped Q-carbon is already viable for applications."

To make the boron-doped Q-carbon, the researchers coated a substrate with a mixture of amorphous carbon and boron. The mixture was then hit with a single laser pulse lasting for only a few nanoseconds.

"By incorporating boron into the Q-carbon we eliminate the material's ferromagnetic properties and give it superconductive properties," Prof Narayan says. "So far, every time we have increased the amount of boron, the temperature at which the material retains its superconductive properties has increased.

"The materials advance here is that this process allows a boron concentration in a carbon material that is far higher than would be possible using existing equilibrium methods, such as chemical vapour deposition.

"Using equilibrium methods, you can only incorporate boron into Q-carbon to 2 atomic percent. Using our laser-based, non-equilibrium process, we've reached levels as high as 27 atomic percent."

According to the researchers, Q-carbon would be suitable for a number of practical applications as it is transparent, superhard, tough, biocompatible, and erosion and corrosion resistant.