Theoretical exploration of external pressure impact on superconducting transition temperatures

Abstract

An external pressure could raise superconducting transition temperatures Tc, which has been experimentally observed but hasn’t been understood systematically. Utilizing superconducting transition temperature equations obtained with Eyring’s rate process theory and free volume concept in our previous work, we have explored how an externally applied pressure could change Tc in this article, under an assumption that the pressure P could change the free volume available for electrons in a system. The electron traveling distance and/or inter-particle spacing between electrons could have a linear, power law, and exponential relationships with pressures, borrowed from the relationship between viscosity and the free volume of molecules for glass liquids. Predicted relationships between Tc and pressures can be used to explain currently observed experimental phenomena such as Tc linearly increasing with pressures, initially slowly increasing and then suddenly jumping to a very high level, or showing skewed saw tooth relationships, etc. Our findings may provide an alternative simple theoretical approach to understand pressure induced superconductivity phenomena, further clearing doubts on many seemingly unrelated experimental observations.