muSR study of carbon-doped MgB2 superconductors

TL;DR

This study investigates how carbon doping affects the superconducting properties of MgB2 using muon spin rotation, revealing a decrease in superconducting gaps and changes in vortex lattice behavior with increased doping.

Contribution

It provides new insights into the effects of carbon doping on the superconducting gaps and vortex lattice properties of MgB2 using TF-muSR measurements.

Findings

Superconducting gaps decrease linearly with increased carbon content.

Doping reduces the depolarisation rate sigma(0), indicating changes in vortex lattice.

The smaller gap is more affected by doping, especially on the 3D pi-sheets.

Abstract

The evolution of the superconducting properties of the carbon-doped MgB2 superconductors, MgB(2-x)Cx (x= 0.02, 0.04, 0.06) have been investigated by the transverse-field muon spin rotation (TF-muSR) technique. The low-temperature depolarisation rate, sigma(0) at 0.6 T which is proportional to the second moment of the field distribution of the vortex lattice decreases monotonically with increasing electron doping and decreasing Tc. In addition, the temperature dependence of sigma(T) has been analysed in terms of a two-gap model. The size of the two superconducting gaps decreases linearly as the carbon content increases, while the doping effect is more pronounced for the smaller gap related to the 3D pi-sheets of the Fermi surface.