Measurement of the magnetic penetration depth of a superconducting MgB$_{2}$ thin film with a large intraband diffusivity

TL;DR

This study measures the temperature-dependent magnetic penetration depth and critical field in a MgB$_{2}$ thin film, revealing the influence of two-band superconductivity and intraband diffusivity differences on superconducting properties.

Contribution

It provides the first detailed analysis of $ ext{MgB}_2$ thin films considering two-gap superconductivity and intraband diffusivity, linking experimental results with theoretical gap equations.

Findings

Larger intraband diffusivity in the 3D $ ext{pi}$ band increases the penetration depth.

Measured $ ext{lambda}$ agrees well with theoretical calculations based on two-gap models.

Results highlight the impact of intraband scattering on superconducting parameters.

Abstract

We report the temperature dependent magnetic penetration depth $\lambda(T)$ and the superconducting critical field $H_{c2}(T)$ in a 500-nm MgB$_{2}$ film. Our analysis of the experimental results takes into account the two gap nature of the superconducting state and indicates larger intraband diffusivity in the three-dimensional (3D) $\pi$ band compared to that in the two-dimensional (2D) $\sigma$ band. Direct comparison of our results with those reported previously for single crystals indicates that larger intraband scattering in the 3D $\pi$ band leads to an increase of $\lambda$. We calculated $\lambda$ and the thermodynamic critical field $H_{c}\approx$2000 Oe employing the gap equations for two-band superconductors. Good agreement between the measured and calculated $\lambda$ value indicates the two independent measurements, such as magnetic force microscopy and transport, provide a venue for investigating superconducting properties in multi-band superconductors.