University of California, San Diego (UCSD) researchers have developed a new way to control the transport of electrical currents through high-temperature superconductors, which "will enable the development of a new generation of superconducting electronics covering a wide spectrum," says UCSD professor Robert Dynes.
The researchers used a facility capable of generating highly focused beams of helium ions to experiment with an approach they believed might avoid previous problems associated with high-temperature conductivity. By using the finely focused helium beam, "we irradiated and hence disordered a nanoscale region of the superconductor to create what is called a 'quantum mechanical tunnel barrier' and were able to write Josephson circuits directly into a thin film of the oxide superconductor," says UCSD physicist Shane Cybart. He notes the researchers used this method to eliminate lithographic processing and produce a straightforward pathway to quantum mechanical circuits operating at more practical temperatures.
The oxide superconductors are very sensitive to point defects in the crystal lattice caused by the ion beam, and increasing irradiation levels increases resistivity and reduces the superconducting transition temperature. "At very high irradiation levels, the superconductor becomes insulating and no longer conducts or superconducts," Cybart notes. "This allows us to use the small helium beam to write these tunnel junctions directly into the material."
From UCSD News (CA)
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