The Superconductivity Phenomenon from the Discovery to the BCS Theory: A Storytelling Approach

Superconductors are the most bizarre among the known materials. Counterintuitive quantum–mechanical effects ensure that, below a critical temperature, they are characterized by zero electrical resistance and by a plenty of unexpected properties, each one of them sufficient to spark the imagination. The superconducting properties are not bound to a particular element or to a crystal structure but to heterogeneous factors that differentiate at microscopic level whose discovery and understanding has interested experimental as well as theoretical research. Recently, unconventional and unexpected superconductivity has been discovered in selected twisted graphene bilayers. Although more than 100 years have passed since the discovery of superconductivity, this finding is an exciting result because graphene, thanks to its simple crystal structure, might be used as an experimental tool to investigate the mechanism of unconventional superconductivity in high Tc superconductors and/or microscopic electronic correlation processes observable at macroscopic level. In this chapter we summarize the relevant achievements in the field of superconductivity, both in the experimental and in the theoretical field, starting from its discovery, up to the BCS theory, and mention the incredible and unique properties of superconductivity that have the potential to revolutionize electrical transmission, transportation, and physics as we know it today. With the goal of giving pedagogical value to this review, we adopted a storytelling approach to summarize the attempts to explain and link the various aspects of the superconductivity, whose range extends from electron–phonon interactions to heavy fermions and massless quasiparticles.