Contact of the intrinsic magnetic topological insulator Mn(Bi,Sb)2Te4 with a superconducting Pb film

Abstract

Intrinsic magnetic topological insulators (MTIs), such as an ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ family, have proved to be an essential platform for the study of various quantum effects and can be used for a range of applications from information storage and dissipationless spin and charge transfer to quantum computers. The latter requires the creation of Majorana fermions, which are expected to emerge when a superconductor is contacted with an MTI surface. Therefore the study of the features arising at the interface between the MTI and the superconductor is of great interest. For this purpose in this paper, the gradual growth of the elemental superconductor (Pb) film on the surface of $\mathrm{Mn}{({\mathrm{Bi}}_{0.7}{\mathrm{Sb}}_{0.3})}_{2}{\mathrm{Te}}_{4}$, which has a Dirac point near the Fermi level, was experimentally investigated by ARPES and XPS methods. We observed that the shape of the Dirac cone state remains almost unchanged up to coverage of $\ensuremath{\sim}1.5$ Pb monolayers, thus remaining topological properties of the material. It was shown that Pb atoms deposition results in surface modification. They detached upper Te atoms and form TePb alloy on the surface. Moreover, Pb deposition leads to disorder of Te, Bi(Sb) layers closest to the surface. As a result, the localization of the Dirac cone state shifts towards the bulk. All these features should be taken into account in the implementation of a topological superconducting state based on the Pb/Mn(Bi,${\mathrm{Sb})}_{2}{\mathrm{Te}}_{4}$ systems.