TEKNIK ELEKTRONIKA

Materials that become superconductive when cooled usually require relative large dimensions, but a research team at Brookhaven National Laboratory, working in collaboration with a team of Israel's Bar-Ilan University, has managed to achieve this with a material formed into nanowires. After fabricating the nanowires, the scientists also discovered that their resistance could be modulated by external magnetic fields. This effect could potentially be used to switch superconductivity on and off magnetically.

The thin-film material, which was cooled to a temperature below approximately 30 degrees Kelvin (-405 degrees Fahrenheit), was made from alternating layers of copper oxide, lanthanum and strontium deposited by molecular beam epitaxy. Electron beam lithography was then used to etch the nanowires, measuring just 25 nanometres in diameter, into a pattern of loops with two different sizes measuring only 150 and 500 nanometres. When an increasing external magnetic field was applied to the wires, the researches found that their resistance was modulated instead of changing linearly as expected. As a result, the researchers hope to engineer a new type of superconducting thin film that allows the superconducting effect to be switched on and off magnetically.

The next objective for the researchers is to discover the mechanism that causes the observed period of the resistance modulation, not only with the aim of developing a new switchable superconducting material but also to increase our understanding of superconductivity. According to the researchers, the observed response to an external magnetic field may help weed out some of the theories that attempt to explain superconductivity, such as potentially discounting the

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