  Over the last decade, the possibility of realizing topological
superconductivity (TSC) has generated much excitement, mainly due to the
potential use of its excitations (Majorana zero modes) in a fault-tolerant
topological quantum computer 1,2. TSC can be created in electronic systems
where the topological and superconducting orders coexist3, motivating the
continued exploration of candidate material platforms to this end. Here, we use
molecular beam epitaxy (MBE) to synthesize heterostructures that host emergent
interfacial superconductivity when a non-superconducting antiferromagnet (FeTe)
is interfaced with a topological insulator (TI) (Bi, Sb)2Te3 wherein the
chemical potential can be tuned through varying the Bi/Sb ratio. By performing
in-vacuo angle-resolved photoemission spectroscopy (ARPES) and ex-situ
electrical transport measurements, we find that the superconducting transition
temperature and the upper critical magnetic field are suppressed when the
chemical potential approaches the Dirac point. This observation implies a
direct correlation between the interfacial superconductivity and Dirac
electrons of the TI layer. We provide evidence to show that the observed
interfacial superconductivity and its chemical potential dependence is the
result of the competition between the Ruderman-Kittel-Kasuya-Yosida-type
ferromagnetic coupling mediated by Dirac surface states and antiferromagnetic
exchange couplings that generate the bicollinear antiferromagnetic order in the
FeTe layer. The Dirac-fermion-assisted interfacial superconductivity in
(Bi,Sb)2Te3/FeTe heterostructures provides a new approach to probe TSC and
Majorana physics in hybrid devices and potentially constitutes an alternative
platform for topological quantum computation.
