title: Robust spin-polarized midgap states at step edges of topological crystalline insulators.
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 nontrivial 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.
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany. sessi@physik.uni-wuerzburg.de.
authors.forename: Paolo
authors.initials: P
authors.lastname: Sessi
authors.affiliation: Institut für Theoretische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Domenico
authors.initials: D
authors.lastname: Di Sante
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Szczerbakow
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Glott
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wilfert
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Henrik
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bathon
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Dziawa
authors.affiliation: Institut für Theoretische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Greiter
authors.affiliation: Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Titus
authors.initials: T
authors.lastname: Neupert
authors.affiliation: Institut für Theoretische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Sangiovanni
authors.affiliation: Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.
authors.forename: Tomasz
authors.initials: T
authors.lastname: Story
authors.affiliation: Institut für Theoretische Physik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Ronny
authors.initials: R
authors.lastname: Thomale
authors.affiliation: Physikalisches Institut, Experimentelle Physik II, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.|Wilhelm Conrad Röntgen-Center for Complex Material Systems (RCCM), Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bode