Topological insulator homojunctions including magnetic layers: the example of n-p type ($n$-QLs Bi$_2$Se$_3$/Mn-Bi$_2$Se$_3$) heterostructures

摘要

Homojunctions between Bi$_2$Se$_3$ and its Mn-doped phase are investigated asa sample geometry to study the influence of spin degrees of freedom ontopological insulator properties. $n$ quintuple layers (QLs) of Bi$_2$Se$_3$are grown ontop of Mn-doped Bi$_2$Se$_3$ by molecular beam epitaxy for $0\le n\le 30\,$QLs, allowing to unhamperedly monitor the development of electronicand topological properties by surface sensitive techniques like angle resolvedphotoemission spectroscopy. With increasing $n$, a Mn-induced gap at the Diracpoint is gradually filled in an "hourglass" fashion to reestablish atopological surface state at $n \sim 9\,$QLs. Our results suggest a competitionof upwards and downwards band bending effects due to the presence of an n-ptype interface, which can be used to tailor topological and quantum well statesindependently.