Superconductivity of Topological Surface States and Strong Proximity Effect in Sn1−xPbxTe–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 can be induced through chemical doping and the proximity effect. However, only conventional full gaps are observed, so the existence of topological superconductivity in topological crystalline insulators is still controversial. Here, the successful fabrication of atomically flat lateral and vertical Sn1−xPbxTe–Pb heterostructures by molecular beam epitaxy is reported. The superconductivity of the Sn1−xPbxTe–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 in the superconducting gap support the presence of the topological superconductivity in superconducting Sn1−xPbxTe. Strong superconducting proximity effect and easy preparation of various constructions between Sn1−xPbxTe and Pb make the heterostructures to be a promising candidate for topological superconducting devices to detect and manipulate Majorana zero modes in the future. Superconducting topological crystalline insulators are expected to form a new type of topological superconductors protected by lattice symmetries. Unconventional peak–dip–hump gap features and fourfold symmetric quasiparticle interference patterns taken at the zero energy in the superconducting gap support the presence of the topological superconductivity in Sn1−xPbxTe–Pb heterostructures. Moreover, the superconducting proximity effect is found to be unexpectedly strong even at 4.2 K.