Miniband engineering and topological phase transitionsin topological-insulator?normal-insulator superlattices
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Periodic stacking of topologically trivial and nontrivial layers with opposite symmetry of the valence andconduction bands induces topological interface states that, in the strong coupling limit, hybridize both acrossthe topological and normal insulator layers. Using band structure engineering, such superlattices (SLs) can beeffectively realized using the IV?VI lead tin chalcogenides. This leads to emergent minibands with a tunabletopology, as demonstrated both by theory and experiments. The topological minibands are proven by magneto-optical spectroscopy, revealing Landau level transitions both at the center and edges of the artificial SL mini-Brillouin zone. Their topological character is identified by the topological phase transitions within the minibandsobserved as a function of temperature. The critical temperature of this transition as well as the miniband gapand miniband width can be precisely controlled by the layer thicknesses and compositions. This witnesses thegeneration of a fully tunable quasi-three-dimensional topological state that provides a template for realization ofmagnetic Weyl semimetals and other strongly interacting topological phases.