Tunneling spectroscopy for probing orbital anisotropy in iron pnictides

TL;DR

This paper demonstrates how tunneling spectroscopy can detect orbital anisotropy and magnetic order in iron pnictides by analyzing impurity effects on local density of states, revealing temperature-dependent phase transitions.

Contribution

It introduces a theoretical framework combining multi-orbital Hamiltonians and T-matrix formalism to identify specific anisotropic signatures in STS related to orbital splitting and magnetic gaps.

Findings

STS signatures track orbital and magnetic gap evolution

Two distinct anisotropic patterns split with temperature

Orbital splitting patterns are related by 90-degree rotation

Abstract

Using realistic multi-orbital tight-binding Hamiltonians and the T-matrix formalism, we explore the effects of a non-magnetic impurity on the local density of states in Fe-based compounds. We show that scanning tunneling spectroscopy (STS) has very specific anisotropic signatures that track the evolution of orbital splitting (OS) and antiferromagnetic gaps. Both anisotropies exhibit two patterns that split in energy with decreasing temperature, but for OS these two patterns map onto each other under 90 degree rotation. STS experiments that observe these signatures should expose the underlying magnetic and orbital order as a function of temperature across various phase transitions.