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Electron-Phonon or Hole Superconductivity in $MgB_2$?

J. E. Hirsch·F. Marsiglio
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Abstract

The BCS electron-phonon mechanism and the unconventional 'hole mechanism' have been proposed as explanations for the high temperature superconductivity observed in $MgB_2$. It is proposed that a critical test of which theory is correct is the dependence of $T_c$ on hole doping: the hole mechanism predicts that $T_c$ will drop rapidly to zero as holes are added, while the electron-phonon mechanism appears to predict increasing $T_c$ for a substantial range of hole doping. Furthermore, the hole mechanism and electron-phonon mechanism differ qualitatively in their predictions of the effect on $T_c$ of change in the $B-B$ distances. We discuss predictions of the hole mechanism for a variety of observables as a function of doping, emphasizing the expected differences and similarities with the electron-phonon explanation. The hole mechanism predicts coherence length and penetration depth to increase and decrease monotonically with hole doping respectively.

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J. E. Hirsch, F. Marsiglio. 2001-04-17. Electron-Phonon or Hole Superconductivity in $MgB_2$?. https://doi.org/10.1103/physrevb.64.144523

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