Study on superconductivity in $$\hbox {Nb}_{{2}}$$ Nb 2 SC and $$\hbox {Nb}_{2}$$ Nb 2 AsC MAX phases at various pressures

Abstract

Abstract $$\hbox {Nb}_{{2}}$$ Nb 2 SC and $$\hbox {Nb}_{{2}}$$ Nb 2 AsC are among the identified superconducting MAX phases, both exhibiting a transition temperature $$\hbox {T}_{{c}}$$ T c lower than 10 K. These compounds appear to belong to the conventional class of superconductors. By calculating the electron-phonon couplings of these materials, we have found that the predicted transition temperatures are approximately 6 K for $$\hbox {Nb}_{{2}}$$ Nb 2 SC and 2 K for $$\hbox {Nb}_{{2}}$$ Nb 2 AsC, closely matching the experimental findings. However, when subjected to pressure or strain, $$\hbox {Nb}_{{2}}$$ Nb 2 SC and $$\hbox {Nb}_{{2}}$$ Nb 2 AsC exhibit contrasting behaviors. While the transition temperature of $$\hbox {Nb}_{{2}}$$ Nb 2 SC can be doubled by applying pressure up to 50 GPa, the transition temperature of $$\hbox {Nb}_{{2}}$$ Nb 2 AsC significantly decreases under the same pressure. On the other hand, in the case of $$\hbox {Nb}_{{2}}$$ Nb 2 AsC, a uniaxial tensile strain of approximately 2% along the c direction can enhance the compound’s transition temperature by about 40%. These results show that with the right pressure or strain, it is possible to increase superconducting transition temperature in the $$\hbox {Nb}_{{2}}$$ Nb 2 AC compounds.

Keywords

• Superconductivity
• MAX phase
• Electron–Phonon