Cleaved surfaces of topological crystalline insulators (TCIs) often exhibit step edges. For example, as highlighted by red and gray spheres, the rendered perspective STM image shows a double- (left) and a single-atomic step edge (right). The periodicity of the surface lattice remains unchanged for the double-atomic step edge (green box; top). In contrast, in the single-atomic case translational symmetry is broken such that pairs of red or grey atoms appear (purple box). This results in the appearance of a conductive channel (rendered image at the bottom) where spin-up and spin- down electrons move into opposite directions.
Science News Discovery of robust spin- polarized edge states on topological crys¬≠tal¬≠line insulators
Topological crystalline insulators (TCIs) are ma¬≠te¬≠ri¬≠als which --similar to the topological insulators (TIs) recently discovered in W√ľrzburg-- exhibit spin-momentum-locked electronic states such that electrons with opposite spin move into con¬≠ver¬≠se directions. This property makes them highly in¬≠ter¬≠es¬≠ting for potential applications, such as sensing or data processing. However, there is one im¬≠por¬≠tant difference between the two meterial classes: whereas TI materials require rather complex pre¬≠pa¬≠ra¬≠tion recipies to fully develop their special elec¬≠tro¬≠nic properties, TCIs intrinsically carry to¬≠po¬≠lo¬≠gi¬≠cal states as a result of their very crystal structure.
In cooperation with colleagues from Polish Aca¬≠de¬≠my of Sciences and Z√ľrich University ex¬≠pe¬≠ri¬≠men¬≠ta¬≠lists and theorists from W√ľrzburg's Faculty of Phy¬≠sics and Astronomy are now reporting the dis¬≠co¬≠ve¬≠ry of a new type of one-dimensional (1D) elec¬≠tro¬≠nic states which exist at step edges of to¬≠po¬≠lo¬≠gi¬≠cal crystalline insulators. They form conductive channels which are only 10 nanometers wide and exhibit a surprising robustness against external perturbations. This may po¬≠ten¬≠tial¬≠ly allow for interconnections between functional units at ultrahigh packing densities.
The result has been published in Science.