Researchers in the US report that they have observed the so-called “fourth signature” of superconducting phase transitions in materials known as cuprates. The result, obtained via photoemission spectroscopy of a cuprate called Bi2212, could shed fresh light on how these materials, which conduct electricity without resistance at temperatures of 77 K or higher, transition into the superconducting state.
The superconducting transition occurs when a material loses all resistance to an electrical current below a certain critical temperature Tc. At this temperature, bulk materials exhibit four characteristic “signatures” – electrical, magnetic, thermodynamic, and spectroscopic – indicating that transition has occurred. The electrical signature is the development of zero resistance. The magnetic signature is the onset of the Meissner effect – that is, the material expels magnetic fields. And the thermodynamic signature is that the material’s heat capacity (the amount of heat required to increase its temperature by a given value) displays a distinctive anomaly.
Engineering Physics, Bachelors of Science, December 1984
Microelectronics & Photonics, Graduate Certificate, February 2016
Nanoengineering, Masters, December 2019
Nanoengineering, Ph.D., Summer 2022
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