Bounds on nanoscale nematicity in single-layer FeSe/SrTiO3

Abstract

We use scanning tunneling microscopy (STM) and quasiparticle interference (QPI) imaging to investigate the low-energy orbital texture of single-layer FeSe/SrTiO3. We develop a T-matrix model of multiorbital QPI to disentangle scattering intensities from Fe 3dxz and 3dyz bands, enabling the use of STM as a nanoscale detection tool of nematicity. By sampling multiple spatial regions of a single-layer FeSe/SrTiO3 film, we quantitatively exclude static xz/yz orbital ordering with domain size larger than δr2=20nm×20nm, xz/yz Fermi wave vector difference larger than δk=0.014π, and energy splitting larger than δE=3.5meV. The lack of detectable ordering pinned around defects places qualitative constraints on models of fluctuating nematicity.