How can pressure affect the superconducting critical temperature of a material?

Pressure serves as a sensitive probe for studying superconductivity because the structural changes it induces significantly influence the critical temperature ($T_c$), which is the threshold below which a material becomes superconducting.1

The effect of pressure on $T_c$ varies depending on the class of material:

• Simple metals: In these materials, increasing pressure generally leads to a decrease in the critical temperature, eventually suppressing the superconducting state entirely.1
• Organic superconductors: For some of these materials, superconductivity is only observed under high-pressure conditions at temperatures near absolute zero.1
• Layered copper-oxide (cuprate) superconductors: In several of these high-temperature superconductors, pressure exerts a strong positive effect, raising the critical temperature. This observation has been instrumental in the synthesis of new superconducting varieties that utilize smaller cations to mimic the structural effects of pressure.1

Because pressure alters the crystal structure, it provides researchers with a valuable tool to investigate how atomic arrangements and structural properties dictate the transition to a superconducting state.1