Charge ordering in stoichiometric FeTe: Scanning tunneling microscopy and spectroscopy

Abstract

We use scanning tunneling microscopy and spectroscopy to reveal a unique stripy charge order in a parent phase of iron-based superconductors in stoichiometric FeTe epitaxy films. The charge order has unusually the same---usually half---period as the spin order. We also found highly anisotropic electron band dispersions being large and little along the ferromagnetic (crystallographic $b$) and antiferromagnetic ($a$) directions, respectively. Our data suggest that the microscopic mechanism is likely of the Stoner type driven by interatomic Coulomb repulsion ${V}_{ij}$, and that ${V}_{ij}$ and charge fluctuations, so far much neglected, are important to the understanding of iron-based superconductors.