Modulation of Electronic Liquid-Crystal Phases by Local Strain in Few-Layer FeSe Films

Symmetry-broken electronic phases bring abundant correlated phenomena into iron-based superconductors. The interplay between subtle lattice distortion and electronic states has drawn sustained interest, yet the underlying microscopic behaviors remain elusive. In this work, we perform a comprehensive scanning tunneling microscopy/spectroscopy study into the lattice structure and electronic smecticity in few-layer FeSe thin films on SrTiO₃(001) substrates. By quantitatively extracting the strain tensor components, we visualize the local strain induced by native line defects including dislocation lines and step-flow edges. Extensive analysis reveals a close dependence of smectic ordering on the structural anisotropy. The smectic stripes preferentially align parallel to the shorter Fe-Fe axis of the distorted orthorhombic lattice, and the line defects help to stabilize larger domain blocks. Our findings unveil a unified picture of the coupling between the crystalline lattice and electronic liquid-crystal states in FeSe, hence providing a pathway to manipulating the electronic phases at the nanoscale.