Superconductivity in MgB2 and Alloys

Magnesium diboride (MgB₂) became a focus of intense research after its surprisingly high superconducting transition temperature of 39 K was discovered in 2001, well above what conventional theory had led physicists to expect for such a simple compound. Its behavior is governed by two distinct superconducting energy gaps arising from separate electron bands, making it a clean experimental window into multi-band superconductivity and the interplay between electrons and lattice vibrations — a coupling strong enough, and shaped by anharmonic phonon effects, to explain much of its unusual character. Researchers are actively working to raise the critical current density — the maximum current MgB₂ can carry while remaining superconducting — through controlled doping with nanoparticles and chemical substitutions, with the goal of making it practical for high-field applications. Open questions remain around how atomic substitutions and disorder redistribute spectral weight between the two gaps, and how anharmonicity and isotope effects constrain the theoretical upper limits of what MgB₂ and related alloys can achieve.

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Keywords

Magnesium DiborideSuperconductivityMultiple GapsAnharmonicityCritical Current DensityTwo-Band Superconductivity