Strong similarities between the local electronic structure of insulating iron pnictide and lightly doped cuprate

TL;DR

This study reveals that insulating iron pnictides exhibit local electronic structures remarkably similar to lightly doped cuprates, suggesting common underlying physics in these unconventional superconductors.

Contribution

It provides the first detailed scanning tunneling microscopy comparison of insulating iron pnictides and lightly doped cuprates, highlighting their electronic similarities.

Findings

Insulating NaFeAs shows an energy gap with low density of states at the Fermi level.

Spectral lineshape and spatial variations resemble lightly doped cuprates.

Cu doping suppresses itinerant electron states, leading to insulating behavior.

Abstract

One of the major puzzles regarding unconventional superconductivity is how some of the most interesting superconductors are related to an insulating phase that lies in close proximity. Here we report scanning tunneling microscopy studies of the local electronic structure of Cu doped NaFeAs across the superconductor to insulator transition. We find that in the highly insulating regime the electronic spectrum develops an energy gap with diminishing density of state at the Fermi level. The overall lineshape and strong spatial variations of the spectra are strikingly similar to that of lightly doped cuprates close to the parent Mott insulator. We propose that the suppression of itinerant electron state and strong impurity potential induced by Cu dopants lead to this insulating iron pnictide.