Imaging the coexistence of superconductivity and a charge density modulation in K0.73Fe1.67Se2 superconductor

TL;DR

This study uses scanning tunneling microscopy to reveal the coexistence of superconductivity and charge density modulation in K0.73Fe1.67Se2, suggesting an electronic superstructure related to magnetic ordering rather than vacancy ordering.

Contribution

It demonstrates the microscopic coexistence of superconductivity and charge density modulation in K0.73Fe1.67Se2, challenging the necessity of vacancy ordering for superconductivity.

Findings

Superconducting gap observed on the FeSe surface.

Charge density modulation with a specific periodicity coexists with superconductivity.

Vacancy ordering is not observed, indicating it is not essential for superconductivity.

Abstract

We report scanning tunneling microscopy studies of the local structural and electronic properties of the iron selenide superconductor K0.73Fe1.67Se2 with TC = 32K. On the atomically resolved FeSe surface, we observe well-defined superconducting gap and the microscopic coexistence of a charge density modulation with root2*root2 periodicity with respect to the original Se lattice. We propose that a possible origin of the pattern is the electronic superstructure caused by the block antiferromagnetic ordering of the iron moments. The widely expected iron vacancy ordering is not observed, indicating that it is not a necessary ingredient for superconductivity in the intercalated iron selenides.