Structural symmetry and superconducting transport in heteroepitaxial FeSe0.4Te0.6/Bi2Se3 systems

Heteroepitaxial FeSe0.4Te0.6/Bi2Se3 heterostructure thin films were successfully grown on CaF2 substrates by pulsed laser deposition. High-resolution structural analysis reveals that atomically sharp interfaces are enabled by the van der Waals bonding nature of both layered constituents. The FeSe0.4Te0.6 films exhibit robust superconductivity with transition temperatures up to 14 K, as confirmed by transport measurements and scanning tunneling spectroscopy, showing well-defined superconducting gaps of Δ ≈ 1.53 meV. Systematic studies indicate that the superconducting properties are highly sensitive to the Bi2Se3 layer thicknesses. These trends reflect a thickness-tunable proximity effect, wherein enhanced hybridization of topological surface states in thinner Bi2Se3 layers strengthens interfacial electronic coupling and Cooper pairing. The demonstrated structural compatibility and controllable superconducting response establish FeSe0.4Te0.6/Bi2Se3 heterostructure as a promising platform for exploring topological superconductivity.