ABSTRACT
The history of superphenomena begins a century ago when Kamerlingh Onnes produces the first liquid helium-4 (in 1908, at the University of Leiden) and uses it as a coolant to study (in 1911) the low-temperature resistance of mercury [1]. Until that time, the idea of working with solidified mercury had been to check the hypothesis that-thanks to the exceptional pureness of the system-the resistivity will tend to zero with vanishing temperature, as opposed to metals with impurities, which feature residual resistance at T → 0. The sudden drop of resistance down to zero (within the experimental resolution) at 4.2K comes as a complete surprise to Onnes. The term “superconductivity” (originally, “supraconductivity”) will be coined by him 2 years later, in 1913, when persistent currents in toroidal samples are observed, proving the practical absence of resistance.
