Effect of transition-metal substitution in iron-based superconductors

TL;DR

This paper theoretically investigates how transition-metal substitution affects iron-based superconductors, revealing impurity effects, doping behavior, and local density of states changes consistent with experimental observations.

Contribution

It provides a theoretical model treating TM ions as impurities, clarifying their role as effective dopants and explaining LDOS evolution in these superconductors.

Findings

TM substitution acts as effective doping.

LDOS becomes V-shaped with impurity increase.

$ ho(0)$ minimizes at optimal doping.

Abstract

We study theoretically the current debatable issue about the effect of transition-metal (TM) substitution in iron-based superconductors through treating all of the TM ions as randomly distributed impurities. The extra electrons from TM elements are localized at the impurity sites. In the mean time the chemical potential shifts upon substitution. The phase diagram is mapped out and it seems that the TM elements can act as effective dopants. The local density of states (LDOS) is calculated and the bottom becomes V-shaped as the impurity concentration increases. The LDOS at the Fermi energy $\rho(\omega=0)$ is finite and reaches the minimum at the optimal doping level. Our results are in good agreement with the scanning tunneling microscopy experiments.