Superconductivity in MgB2 and Alloys

Magnesium diboride (MgB₂) became a focus of intense research after its superconducting transition temperature of 39 K was discovered in 2001, unexpectedly high for a simple binary compound and explained by unusually strong coupling between electrons and lattice vibrations. Unlike conventional superconductors, MgB₂ carries two distinct energy gaps arising from its two-band electronic structure, a feature that complicates but also enriches the theoretical picture of how Cooper pairs form and break. Much of the current work centers on pushing the material toward practical applications by improving the critical current density — the threshold beyond which superconductivity collapses under an applied current — through nanoparticle doping and alloying strategies that introduce controlled disorder. Open questions remain around the role of anharmonic lattice dynamics in setting the transition temperature and around how the two-band character evolves in high magnetic fields or when the boron isotope is substituted, tests that probe the microscopic mechanism at its roots.

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Keywords

Magnesium DiborideSuperconductivityMultiple GapsAnharmonicityCritical Current DensityTwo-Band Superconductivity