Two-band effects in transport properties of MgB2

TL;DR

This study investigates the transport properties of MgB2, revealing two-band conduction effects through resistivity and thermal conductivity measurements on samples with varying purity levels.

Contribution

It provides experimental evidence of two-band effects in MgB2's transport properties, highlighting the impact of sample purity on conduction mechanisms.

Findings

Higher thermal conductivity in high-purity samples.

Residual resistivity significantly lower in cleaner samples.

Temperature resistivity coefficient varies with sample purity.

Abstract

We present resistivity and thermal conductivity measurements on bulk samples, prepared either by a standard method or by a one-step technique. The latter samples, due to their high density and purity, show residual resistivity values as low as 0.5 mW cm and thermal conductivity values as high as 215 W/mK, higher than the single crystal ones. Thermal and electrical data of all the samples are analysed in the framework of the Bloch-Gruneisen equation giving reliable parameter values. In particular the temperature resitivity coefficient, obtained both from resistivity and thermal conductivity, in the dirty sample comes out ten time larger than in the clean ones. This result supports the hypothesis of ref. [1] that p and s bands conduct in parallel, prevailing p conduction in clean samples and s conduction in dirty samples .