Topological Homojunction

Topological Homojunctions

In a Bi₂Se₃ superlattice, you can obtain topological interface states by applying tensile strain in certain layers only (read more about this effect in Strain & Topological Interface States). In such a system the bulk-to-boundary (which dictates that a topological interface state must arise at the junction between two materials with different topologcal invariants) correspondence can be probed with the smallest possible number of different elements, since both subsystems at the interface will have the same crystal symmetries and chemical composition (and can even have the same electronic gap!). Thus, this topological homojunction can righteously be called the 'Hydrogen atom' of topological states of matter, in the sense that it is the simplest possible scenario for topological states to develop.