Strong Superconducting Proximity Compatible with Fermi-Level Tuning at Top Surfaces of Bulk Insulating SnTe-Type Semiconductors.

Abstract

The signature of multiple Majorana zero modes (MZMs) was recently observed in a single vortex of topological crystalline insulator SnTe. However, to directly distinguish the MZMs, the Fermi level should be very close to the Dirac points of topological surface states and thus be inside the insulating bulk bandgap, leading to a significant suppression of proximity-induced superconductivity in the vertical heterostructure. Here, we demonstrate that both the strong superconducting proximity effect and the small Fermi energy can be simultaneously satisfied in the lateral heterostructures composed of SnTe-type semiconductors and Pb. Even though the region is bulk insulating with only a few surface states crossing the Fermi level, the surface superconductivity can still be transferred over a long distance at 4.2 K, indicating high device stability with lateral superconducting proximity. Our findings suggest that the lateral two-sided heterostructure is a promising platform for further detecting the evolution of multiple MZMs.