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

Abstract

That very strong coupling of the B-B bond-stretching E2g branch of phonons to the B 2pσ bonding hole states is responsible for the remarkable superconductivity in MgB 2 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.

Substitution ofScforMginMgB2Agrestini1, Metallo2, Filippi3 et al. 2004Phys. Rev. B823720View full textAdd to dashboardCite

“…The substituted Sc ions donate 0.12<x<0.27 electrons per unit cell to the conduction σ and π bands so the chemical potential is shifted towards the top of the σ band beyond the ETT 6 where the σ Fermi surface changes from a 2D to a 3D topology, expected near x=0.12 9,18 . Sc substitution for Mg increases the disorder in the Mg/Sc layers but has minor effects on the lattice structure of the boron layer.…”

Design for a Room-Temperature Superconductor

“…38,39,40 Nevertheless, its predictions seem to be reasonable for MgB 2 , so it is reasonable for us to extrapolate the theory to include more phonons with similar strength of coupling. 4.…”

Is MgB2a BCS-like charged superfluid?

“…This mechanism has been strongly advocated by Pickett and co-workers [4,5], though the electron-phonon interaction has to be surprisingly strong to yield the measured transition temperature T c ¼ 39:4 K. However, we have added to the BCS-like plot in figure 2 this material MgB 2 , and this lies on the scaled BCS-like curve, both within McMillan's approximation [6,7] …”

“…To conclude, it is important to add that Feshbach resonances have been proposed by Bianconi and co-workers [10] as a complementary mechanism to that of An and Pickett [4,5]. Both references [10] and [11] invoke the multiband nature of the electronic structure of MgB 2 .…”