Eur. Phys. J. B 30, 511-517 (2002)
https://doi.org/10.1140/epjb/e2002-00408-2

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

¹ Dipartimento di Fisica, Universitá “La Sapienza", P.le A. Moro 2, 00185 Roma, and INFM-SMC Roma1, Italy
² École Polytechnique Fédérale de Lausanne, IPR-LPM, 1015 Lausanne, Switzerland
³ Istituto di Acustica “O.M. Corbino”, CNR, Area di Ricerca Tor Vergata, Roma, Italy

Corresponding author: ^a emmcapp@pil.phys.uniromal.it

Received: 31 July 2002
Revised: 21 September 2002
Published online: 31 December 2002

Abstract

In small Fermi energy metals, disorder can deeply modify superconducting state properties leading to a strong suppression of the critical temperature T_c. 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 . We find that as soon as 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.