Rotation of the dislocation grid in multilayer FeSe films and visualization of electronic nematic domains via orbital-selective tunneling

TL;DR

This study visualizes dislocation networks and electronic nematic domains in multilayer FeSe films, revealing how strain and dislocation rotation influence nematicity, using advanced microscopy and spectroscopy techniques.

Contribution

It demonstrates the direct visualization of dislocation networks and their rotation in FeSe films, linking strain patterns to electronic nematic domain behavior with orbital-selective tunneling.

Findings

Dislocation networks rotate by 45 degrees with film thickness.

Strain affects coupling ratios between nematic domains.

Differential conductance reveals orthogonal nematic domains.

Abstract

Understanding the interplay of structural and electronic symmetry breaking in Fe-based high temperature superconductors remains of high interest. In this work we grow strain-patterned multilayer FeSe thin films in a range of thicknesses using molecular beam epitaxy. We study the formation of electronic nematic domains and spatially-varying strain using scanning tunneling microscopy and spectroscopy. We directly visualize the formation of edge dislocations that give rise to a two-dimensional edge dislocation network in the films. Interestingly, we observe a 45 degree in-plane rotation of the dislocation network as a function of film thickness, yielding antisymmetric strain along different directions. This results in different coupling ratios between electronic nematic domains and antisymmetric strain. Lastly, we are able to distinguish between different orthogonal nematic domains by revealing a small energy-dependent difference in differential conductance maps between the two regions. This could be explained by orbital-selective tip-sample tunneling. Our observations bring new insights into the dislocation network formation in epitaxial thin films and provide another nanoscale tool to explore electronic nematicity in Fe-based superconductors.