Interaction Effects in a 1D Flat Band at a Topological Crystalline Step Edge

Step edges of topological crystalline insulators can be viewed as predecessors of higher-order topology, as they embody one-dimensional edge channels embedded in an effective three-dimensional electronic vacuum emanating from the topological crystalline insulator. Using scanning tunneling microscopy and spectroscopy, we investigate the behavior of such edge channels in Pb1-xSnxSe under doping. Once the energy position of the step edge is brought close to the Fermi level, we observe the opening of a correlation gap. The experimental results are rationalized in terms of interaction effects which are enhanced since the electronic density is collapsed to a one-dimensional channel. This constitutes a unique system to study how topology and many-body electronic effects intertwine, which we model theoretically through a Hartree-Fock analysis.

Automated summary

Step edges of topological crystalline insulators in Pb1-xSnxSe were studied using scanning tunneling microscopy and spectroscopy. When the energy position of the step edge approaches the Fermi level, a correlation gap opens up. The experimental results suggest that the interaction effects are enhanced due to the collapsing of electronic density into a one-dimensional channel, providing a unique system to study the intertwining of topology and many-body electronic effects. Theoretical modeling was performed through a Hartree-Fock analysis.