Carbon "buckyballs" briefly become high-temperature superconductor when hit with ultrafast laser pulses

The most-well-known carbon fullerene, C₆₀, otherwise known as a buckyball, when made into a potassium-containing compound with the chemical formula K₃C₆₀, can normally behave as a superconductor below a critical temperature of 20 K. It has now been discovered that K₃C₆₀ transforms into a high-temperature superconductor when struck by an ultrafast laser pulse.¹

The material takes on superconductive properties, albeit extremely briefly, up to a temperature of -73°C, almost 100 degrees above the critical equilibrium temperature. The research explains the reason for this mysterious behaviour.

The researchers who discovered this have affiliations with a long list of institutions including the International School for Advanced Studies (SISSA; Trieste, Italy), Interdisciplinary Laboratories for Advanced Materials Physics (ILAMP; Brescia, Italy), Centre de Physique Théorique, Ećole Polytechnique, CNRS (Palaiseau, France), Collége de France (Paris, France, University of Geneva (Geneva, Switzerland), International Centre for Theoretical Physics (ICTP; Trieste, Italy), and CNR-IOM Democritos (Trieste, Italy)

K₃C₆₀ is a compound in which purely molecular features coexist alongside metallic properties, a characteristic shared by so-called strongly correlated materials. According to the theory developed by the researchers in this study, the laser beam creates a high-energy molecular excitation, yet in order to do so it must absorb heat from the low-energy metallic component, which thus cools. As it is specifically the metallic component involved in conduction, its cooling may lead to a superconductivity phase despite the fact that the external temperature is higher than the critical temperature.

As the researchers explain: "It is an example of laser cooling, yet with a new operating mechanism which had never been proposed until now. The fact that the laser pulse can transiently change the characteristics of a material is a significant observation. It may offer the prospect of manufacturing electronic devices whose properties change with the use of light, as if it were a switch. Indeed, the ultrarapid control of materials with light sources is of great current interest for the scientific community and for the possible technological ramifications of these applications."

Source: https://www.sissa.it/news/laser-beams-superconductivity

REFERENCE:

1. Andrea Nava et al., Nature Physics (2017); doi: 10.1038/nphys4288