One Step Closer to Room Temperature Superconductors

Tag : Ceramic Insulators

The quest for room temperature superconductivity has grippedphysics researchers since they saw the possibility more than twodecades ago. Unfortunately, scientists have been unable to decipherhow copper oxide materials superconduct at extremely coldtemperatures (such as that of liquid nitrogen), much less designmaterials that can superconduct at higher temperatures.
Materials that are known to superconduct at the highesttemperatures are, unexpectedly, ceramic insulators that behave asmagnets before 'doping' (the method of introducing impurities to asemiconductor to modify its electrical properties). Upon dopingcharge carriers (holes or electrons) into these parent magneticinsulators, they mysteriously begin to superconduct, i.e. the dopedcarriers form pairs that carry electricity without loss.
The essential conundrum facing researchers in this area has been:how does a magnet that cannot transport electricity transform intoa superconductor that is a perfect conductor of electricity? TheCambridge team have made a significant advance in answering thisquestion.
The researchers have discovered where the charge 'hole' carriersthat play a significant role in the superconductivity originatewithin the electronic structure of copper-oxide superconductors.These findings are particularly important for the next step ofdeciphering the glue that binds the holes together and determiningwhat enables them to superconduct.
Dr Suchitra E. Sebastian, lead author of the study, commented,"An experimental difficulty in the past has been accessing theunderlying microscopics of the system once it begins tosuperconduct. Superconductivity throws a manner of 'veil' over thesystem, hiding its inner workings from experimental probes. A majoradvance has been our use of high magnetic fields, which punch holesthrough the superconducting shroud, known as vortices - regionswhere superconductivity is destroyed, through which the underlyingelectronic structure can be probed.
"We have successfully unearthed for the first time in a hightemperature superconductor the location in the electronic structurewhere 'pockets' of doped hole carriers aggregate. Our experimentshave thus made an important advance toward understanding howsuperconducting pairs form out of these hole pockets."
By determining exactly where the doped holes aggregate in theelectronic structure of these superconductors, the researchers havebeen able to advance understanding in two vital areas:
(1) A direct probe revealing the location and size of pockets ofholes is an essential step to determining how these particles sticktogether to superconduct.
(2) Their experiments have successfully accessed the region betwixtmagnetism and superconductivity: when the superconducting veil ispartially lifted, their experiments suggest the existence ofunderlying magnetism which shapes the hole pockets. Interplaybetween magnetism and superconductivity is therefore indicated -leading to the next question to be addressed.
Do these forms of order compete, with magnetism appearing in thevortex regions where superconductivity is killed, as they suggest?Or do they complement each other by some more intricate mechanism?One possibility they suggest for the coexistence of two verydifferent physical phenomena is that the non-superconducting vortexcores may behave in concert, exhibiting collective magnetism whilethe rest of the material superconducts.