Superconductivity of Topological Surface States and Strong Proximity Effect in Sn_{1- x}Pb_xTe-Pb Heterostructures

Superconducting topological crystalline insulators are expected to form a new type of topological superconductors to host Majorana zero modes under the protection of lattice symmetries. The bulk superconductivity of topological crystalline insulators has been induced through chemical doping and proximity effect. However, only conventional full gaps are observed, so the existence of topological superconductivity in topological crystalline insulators is still controversial. Here, we report the successful fabrication of atomically flat lateral and vertical Sn_1-xPb_xTe-Pb heterostructures by molecular beam epitaxy. The superconductivity of the Sn_1-xPb_xTe-Pb heterostructures can be directly investigated by scanning tunneling spectroscopy. Unconventional peak-dip-hump gap features and fourfold symmetric quasiparticle interference patterns taken at the zero energy support the presence of the topological superconductivity in superconducting Sn_1-xPb_xTe. Strong superconducting proximity effect and easy preparation of various constructions between Sn_1-xPb_xTe and Pb make the heterostructures to be a promising candidate for topological superconducting devices to detect and manipulate Majorana zero modes in the future.