Scientists using copper-based materials and some new approaches have investigated how unconventional superconductors might be able to work at near-room-temperatures.
Superconductivity is a phenomenon of complete disappearance of electrical resistance in different materials when such materials are cooled below a ‘critical temperature'. This temperature varies for different types of materials but is usually below 20 degrees Kelvin (-253 degrees Celsius). In superconductors, electrons condense into a state that enables passing of electrical current with zero loss.
Scientists have been trying to develop new types of superconductors able to work at or close to room temperature, thereby opening a new route for creating far more powerful computers. To develop such superconducting materials, scientists first need to find out the factors that trigger superconductivity in some materials at relatively high temperatures.
Now in two separate studies, researchers from Stanford University and SLAC National Accelerator Laboratory have reported some important advances in functioning of high-temperature superconductors in two separate studies. They claim that they were able to measure the collective vibrations of electrons and also demonstrate how collective interactions of the electrons along with some other factors can help boost superconductivity.
In the first study, scientists at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL) examined the effect of doping - adding a chemical that changes the density of electrons in a material - on different properties (including superconductivity) of a cuprate called bismuth strontium calcium copper oxide (Bi2212).
With the assistance of researchers working at the National Institute of Advanced Industrial Science and Technology in Japan, the SSRL team prepared various samples of Bi2212 with different levels of doping. These samples were then examined with angle-resolved photo-emission spectroscopy.
The findings revealed that the maximum superconducting temperature of Bi2212 peaked with increasing levels of doping and then fell off again. The results also indicated that even small changes in the doping can produce significant changes in superconductivity and in the interaction of electrons with lattice vibrations.
The second study that was carried out at the European Synchrotron Radiation Facility in France focused on studying the collective behaviour of electrons in samples of layered cuprates, called NCCO and LCCO. Researchers used a resonant inelastic X-ray scattering technique to observe the propagation of acoustic plasmons through the whole lattice in these layered cuprate high temperature superconductors.
The results indicated that layered structure also affects the behaviour of electrons in a profound way in these superconducting materials.
Image, above: Standford University study reveals how coordinated motions of copper (red) and oxygen (grey) atoms in a high-temperature superconductor boost the superconducting strength of pairs of electrons (white glow), allowing the material to conduct electricity without any loss at much higher temperatures. The discovery opens a new path to engineering higher-temperature superconductors
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