Aluminium and carbon doped MgB2: band filling, band shift, and anisotropy loss

TL;DR

This study investigates how Carbon and Aluminium doping affect the electronic structure and superconducting properties of MgB2, revealing band filling, band shifts, and anisotropy loss as key factors influencing Tc and conductivity.

Contribution

It demonstrates that the rigid band approximation effectively models doping effects on MgB2's band structure and superconductivity, highlighting the role of anisotropy loss.

Findings

Doping causes band filling and relative band shifts.

The RBA accurately predicts band structure changes with doping.

Superconducting Tc correlates with sigma-band density of states, modulated by anisotropy loss.

Abstract

In this work the effect of Carbon and Aluminium doping on the multiband MgB2 superconductor is analyzed. Using the rigid band and virtual crystal approximations (RBA and VCA), it was found that the main effect of doping on the band structure is band filling and a relative band-shift. If this band-shift is eliminated with an appropriate change of scale, then the RBA provides a good description of the band structure as function of doping. With this procedure both the inplane electrical conductivity of the C- and Al-doped MgB2 and the superconducting critical temperature follow the same curve. The Tc graph approximately follows the sigma-band density of states; the differences between these two can be explained by loss of anisotropy which plays an important role in these systems.