Electron-phonon coupling in MgB2-like materials: its magnitude and its limits

That very strong coupling of the B-B bond-stretching E2g branch of phonons to the B 2psigma bonding hole states is responsible for the remarkable superconductivity in MgB2 is well established. This entirely new manner of driving the superconducting Tc to high levels requires additional analysis. Here recent findings, such as how this strong coupling is related to possible structural instability, are discussed, and investigation into the practical limits of such coupling is initiated