Light to control superconductors

The superconductivity is a phenomenon that occurs in some particular materials where the electrical resistance almost zeroes at critical temperatures close to absolute zero, that is to say 0K (zero Kelvin degrees), value equivalent to −273°C. In some ceramic materials, the phenomenon occurs at higher temperatures, like in the case of a ceramic compound constituted by mercury, barium, calcium, copper and oxygen, where the critical temperature is 138K, corresponding to -135°C. Considering the notable applications that might be based on the superconductivity, scientists have always researched the “perfect superconductor”, that is to say able of superconductivity at environmental temperature, overcoming the current limits imposed by the need of operating at very low temperatures, and currently the focus is on the study of superconductors based on metals. A pool of academic research centres constituted by Scuola Internazionale Superiore di Studi Avanzati in Trieste (SISSA), the Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) of Università Cattolica del Sacro Cuore in Brescia, by the Physics Department of Trieste University and by the T-REX laboratory of Elettra Sincrotrone, still in Trieste, have studied in-depth a particular phenomenon called “pseudogap”. In detail, when a material is heated above its critical temperature (at which superconductivity emerges), some characteristics of its superconductive state remain unchanged even if the most important one, zero electrical resistance, is lost. Researchers induced the pseudogap condition in the material, then subjecting it to very short laser light pulses, which made it temporarily more “metallic”, state, the latter, that generally does not occur in the pseudogap condition, with electrons freely flowing. Once ended the light stimulation, they ascertained they had induced a transient state, even if for an even infinitesimal duration of a picosecond, where the light had removed the electron-electron interactions responsible for the pseudogap.