Impurity, phonon and electron contributions to the electrical resistivity of single-crystalMgB2

Abstract

The electrical resistivity of the MgB2 superconductor is calculated from the generalized Bloch–Gruneisen equation, and anoverlap repulsive potential is used to generate the acoustic and optical phonon frequencies.Due to two inherent energy gaps, the elastic scattering of electrons from impurities wasestimated first. Within a two-band picture, the impurity-limited resistivity due toπ band carriersρ0π is larger than thecontribution from σ band carriers. The interband impurity scattering is assumed to benegligible compared with intraband scattering. The inelastic scattering ofσ band carriers with acoustic phonons dominates over that of theπ band carriers with optical phonons belowT≈θD/2. At roomtemperature the slope dρπ/dT is larger. The temperature dependence of resistivity of acoustic phonons with a Debye temperatureθD≈450 K and high-energy optical phonons with an Einstein temperatureθE≈966 K, along with the limited resistivity of impurity scatterers, when subtracted from single-crystaldata, infers a power temperature dependence over most of the temperature range(40 K≤T≤300 K). The quadratic temperature dependence ofρdiff = [ρexp−{ρ0+ρe−ph(= ρe−phπ+ρe−phσ)}] is understood in terms of inelastic electron–electron scattering. The comparison oftransport parameters with single-crystal data appears to be consistent within the two-bandscheme for resistivity that we have presented.