Quasiparticle Interference in the Unconventional Metamagnetic Compound Sr$_3$Ru$_2$O$_7$

TL;DR

This study uses spectroscopic imaging STM and theoretical modeling to analyze quasiparticle interference in Sr$_3$Ru$_2$O$_7$, revealing orbital band structures, nesting features, and nematic symmetry breaking.

Contribution

It provides a detailed theoretical calculation of QPI spectra incorporating complex band features, matching experimental Fermi surface data and exploring nematic state effects.

Findings

QPI spectra show a hollow square-like feature from orbital nesting.

Theoretical results agree with recent ARPES measurements.

Nematic order causes detectable symmetry breaking in QPI patterns.

Abstract

Quasiparticle interference (QPI) in spectroscopic imaging scanning tunneling microscopy provides a powerful method to detect orbital band structures and orbital ordering patterns in transition metal oxides. We use the $T$-matrix formalism to calculate the QPI spectra for the unconventional metamagnetic system of Sr$_3$Ru$_2$O$_7$ with a $t_{2g}$-orbital band structure. A detailed tight-binding model is constructed accounting for features such as spin-orbit coupling, bilayer splitting, and the staggered rotation of the RuO octahedra. The band parameters are chosen by fitting the calculated Fermi surfaces with those measured in the angular-resolved photo-emission spectroscopy experiment. The calculated quasiparticle interference at zero magnetic field exhibits a hollow square-like feature arising from the nesting of the quasi-1d $d_{xz}$ and $d_{yz}$ orbital bands, in agreement with recent measurements by J. Lee {\it et al.} (Nature Physics {\bf 5}, 800 (2009)). Rotational symmetry breaking in the nematic metamagnetic state also manifests in the quasi-particle interference spectra.