In many superconductors, phonons play a crucial role in pairing up electrons (Cooper pairs), enabling superconductivity. The frequency of phonons affects the strength of this pairing and, in turn, determines the highest possible temperature (TC) at which superconductivity can occur.
Since fundamental constants impose an upper limit on phonon frequencies, they also place a theoretical constraint on how high TC can be in superconductors. This means that “the upper limit of superconducting temperature TC is intrinsically linked to the fundamental constants of nature – the electron mass, electron charge, and the Planck constant,” the study authors note.
So what’s the upper limit?
Using the fundamental constants, the study authors determined that superconductivity can exist between a temperature of 100 Kelvin to 1000 Kelvin; this upper limit range for TC includes standard room temperature values that lie between 293 K to 298 K (20 to 25°C).