Robust spin-polarized midgap states at step edges of topological crystalline insulators

Paolo Sessi; Domenico Di Sante; Andrzej Szczerbakow; Florian Glott; Stefan Wilfert; Henrik Schmidt; Thomas Bathon; Piotr Dziawa; Martin Greiter; Titus Neupert; Giorgio Sangiovanni; Tomasz Story; Ronny Thomale; Matthias Bode

doi:10.1126/science.aah6233

arXiv · 1612.07026

Robust spin-polarized midgap states at step edges of topological crystalline insulators

Paolo Sessi·Domenico Di Sante·Andrzej Szczerbakow·Florian Glott·Stefan Wilfert·Henrik Schmidt·Thomas Bathon·Piotr Dziawa·Martin Greiter·Titus Neupert·Giorgio Sangiovanni·Tomasz Story·Ronny Thomale·Matthias Bode

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Abstract

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.

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Paolo Sessi, Domenico Di Sante, Andrzej Szczerbakow, Florian Glott, Stefan Wilfert, Henrik Schmidt, Thomas Bathon, Piotr Dziawa, Martin Greiter, Titus Neupert, Giorgio Sangiovanni, Tomasz Story, Ronny Thomale, Matthias Bode. 2016-12-21. Robust spin-polarized midgap states at step edges of topological crystalline insulators. https://doi.org/10.1126/science.aah6233

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