Topological insulator homojunctions including magnetic layers: The example of n-p type (n-QLs Bi₂Se₃/Mn-Bi₂Se₃) heterostructures

Homojunctions between Bi₂Se₃ and its Mn-doped phase are investigated as a sample geometry to study the influence of spin degrees of freedom on topological insulator properties. n quintuple layers of Bi₂Se₃ are grown on top of Mn-doped Bi₂Se₃ by molecular beam epitaxy for $0≤n≤30 QLs$⁠, allowing to unhamperedly monitor the development of electronic and topological properties by surface sensitive techniques like angle resolved photoemission spectroscopy. With increasing n, a Mn-induced gap at the Dirac point is gradually filled in an “hourglass” fashion to reestablish a topological surface state at $n∼9 QLs$⁠. Our results suggest a competition of upward and downward band bending effects due to the presence of an n-p type interface, which can be used to tailor topological and quantum well states independently.