Surface orbital order and chemical potential inhomogeneity of the iron-based superconductor FeTe0.55Se0.45 investigated with special STM tips

TL;DR

This study uses specialized STM tips to explore surface orbital order and chemical potential inhomogeneity in FeTe0.55Se0.45, revealing vortex states linked to local topological variations.

Contribution

The paper introduces a novel STM approach with manipulated tip states to probe orbital and chemical potential inhomogeneities in an iron-based superconductor.

Findings

Identification of orbital signatures of subsurface Fe layer.

Observation of intrinsic chemical potential inhomogeneity.

Detection of three types of vortex bound states.

Abstract

The atomically clean surface of the iron-based superconductor FeTe0.55Se0.45 is investigated by low-temperature STM with different tip apex states. By manipulating a single Fe atom onto the tip apex, signatures of the orbital nature of the subsurface Fe layer of FeTe0.55Se0.45 can be identified. By preparing a charged tip state, the intrinsic spatial inhomogeneity of the chemical potential of FeTe0.55Se0.45 can be revealed. As a result, three different types of vortex bound states originating from locally varying topological properties of the FeTe0.55Se0.45 surface are observed by scanning tunneling spectroscopy.