Doped holes and/or electrons induced superconductivity domes explained with the free volume concept

Abstract The conductivity equation developed in our previous work without any restrictions to specific materials is employed to explore how superconductivity transition temperature $$T_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> changes with the doped hole or electron concentrations based on the free volume concept. The predicted relationship is used to fit experimental data available in the literature and a good agreement with observations is achieved. Our findings may provide an alternative explanation for doping-induced domes and/or double domes with a-dip phenomena observed among many superconductors.