Spin susceptibility in small Fermi energy systems: effects of nonmagnetic impurities

Original · EN

In small Fermi energy metals, disorder can deeply modify superconducting state properties leading to a strong suppression of the critical temperature Tc. In this paper, we show that also normal state properties can be seriously influenced by disorder when the Fermi energy E F is sufficiently small. We calculate the normal state spin susceptibility χ for a narrow band electron-phonon coupled metal as a function of the non-magnetic impurity scattering rate γ imp. We find that as soon as γ imp is comparable to E F, χ is strongly reduced with respect to its value in the clean limit. The effects of the electron-phonon interaction including the nonadiabatic corrections are discussed. Our results strongly suggest that the recent finding on irradiated MgB₂ samples can be naturally explained in terms of small E F values associated with the σ-bands of the boron plane, sustaining therefore the hypothesis that MgB₂ is a nonadiabatic metal.