Topological crystalline insulators are materials in which the crystalline symmetry leads to topologically protected surface states with a chiral spin texture, rendering them potential candidates for spintronics applications. Using scanning tunneling spectroscopy, we uncover the existence of one-dimensional (1D) midgap states at odd-atomic surface step edges of the three- dimensional topological crystalline insulator (Pb,Sn)Se. A minimal toy model and realistic tight- binding calculations identify them as spin-polarized flat bands connecting two Dirac points. This non-trivial origin provides the 1D midgap states with inherent stability and protects them from backscattering. We experimentally show that this stability results in a striking robustness to defects, strong magnetic fields, and elevated temperature.
@article{arxiv.1612.07026,
title = {Robust spin-polarized midgap states at step edges of topological crystalline insulators},
author = {Paolo Sessi and Domenico Di Sante and Andrzej Szczerbakow and Florian Glott and Stefan Wilfert and Henrik Schmidt and Thomas Bathon and Piotr Dziawa and Martin Greiter and Titus Neupert and Giorgio Sangiovanni and Tomasz Story and Ronny Thomale and Matthias Bode},
journal= {arXiv preprint arXiv:1612.07026},
year = {2016}
}