Spectroscopic Imaging Scanning Tunneling Microscopy as a Probe of Orbital Structures and Ordering

TL;DR

This paper proposes a spectroscopic imaging scanning tunneling microscopy method to detect and analyze orbital structures and ordering in transition metal oxides through quasiparticle interference patterns.

Contribution

It introduces a theoretical approach using QPI patterns in spectroscopic imaging STM to probe orbital degrees of freedom and their ordering, which are otherwise difficult to detect.

Findings

QPI patterns reveal stripe-like features in $d_{xz}$ and $d_{yz}$ orbitals.

Orbital ordering causes nematic distortion in QPI patterns.

Method is robust against orbital hybridization.

Abstract

Unlike charge and spin, the orbital degree of freedom of electrons in transition metal oxides is difficult to detect. We present the theoretical study of a new detection method in metallic orbitally active systems by analyzing the quasiparticle scattering interference (QPI) pattern of the spectroscopic imaging scanning tunneling spectroscopy, which is sensitive to orbital structures and orbital ordering. The QPIs for the $d_{xz}$ and $d_{yz}$-orbital bands in the $t_{2g}$-orbital systems show a characteristic stripe-like feature as a consequence of their quasi-one-dimensional nature, which is robust against orbital hybridization. With the occurrence of orbital ordering proposed in Sr$_3$Ru$_2$O$_7$ and iron-pnictides, the stripe-like QPI patterns exhibit nematic distortion breaking the $C_4$-symmetry.