Electron-Hole Asymmetry in Superconductivity of Pnictides Originated from the Observed Rigid Chemical Potential Shift

TL;DR

This study uses photoemission to analyze chemical potential shifts in BaFe$_2$As$_2$-based pnictides, revealing electron-hole asymmetry that supports Fermi surface nesting as a key factor in superconductivity.

Contribution

It provides experimental evidence for rigid band shifts and electron-hole asymmetry, linking band structure effects to superconductivity in iron pnictides.

Findings

Chemical potential shift aligns with rigid band predictions.

Electron-hole asymmetry affects Fermi surface nesting.

Asymmetry explains the superconducting dome shape.

Abstract

We have performed a systematic photoemission study of the chemical potential shift as a function of carrier doping in a pnictide system based on BaFe$_2$As$_2$. The experimentally determined chemical potential shift is consistent with the prediction of a rigid band shift picture by the renormalized first-principle band calculations. This leads to an electron-hole asymmetry (EHA) in the Fermi surface (FS) nesting condition due to different effective masses for different FS sheets, which can be calculated from the Lindhard function of susceptibility. This built-in EHA from the band structure, which matches well with observed asymmetric superconducting domes in the phase diagram, strongly supports FS near-nesting driven superconductivity in the iron pnictides.