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

The material could someday be used as an ultrafast switch.

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."



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

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