Scaling of Hall Resistivity in the Mixed State of MgB2 Films

TL;DR

This study investigates the scaling behavior of Hall resistivity in MgB2 thin films' mixed state, revealing how vortex pinning and quasiparticle proliferation affect resistivity scaling across different magnetic fields.

Contribution

It provides detailed analysis of the field-dependent scaling law of resistivities in MgB2, linking vortex dynamics and multi-band effects to resistivity behavior.

Findings

Beta remains at 2.0 below 1T due to weak vortex pinning.

Beta drops sharply around 2T due to quasiparticle proliferation.

Beta approaches 2.0 again at high fields as vortex pinning weakens.

Abstract

The longitudinal resistivity (rho_{xx}) and transverse resistivity (rho_{xy}) of MgB2 thin films in the mixed state were studied in detail. We found that the temperature dependencies of rho_{xx} and \rho_{xy} at a fixed magnetic field (H) satisfy the scaling law of $\rho_{xy}=A\rho_{xx}^\beta$, where the exponent beta varies around 2.0 for different fields. In the low field region (below 1T), beta maintains a constant value of 2.0 due to the weak pinning strength of the vortices, mainly from the superfluid of the pi band. When H>1T, beta drops abruptly to its lowest value at about 2T because of the proliferation of quasiparticles from the pi-band and, hence, the motion of the vortices from the superfluid of the sigma-band dominates the dissipation. As the field is increased further, the vortex pinning strength is weakened and beta increases monotonically towards 2.0 at a high field. All the results presented here are in good agreement with the expectation of the vortex physics of a multi-band superconductor.