Superconducting proximity effect in PbTe-Pb hybrid nanowires*

A semiconductor nanowire coupled to a superconductor is an intriguing quantum system owing to the proximity effect. One example is the gate-tunable Josephson junction, which plays a key role in the gatemon superconducting qubit. Moreover, the interplay between strong spin-orbit coupling of the semiconductor and Zeeman energy may lead to topological phases hosting Majorana zero modes.
So far, most of those studies are based on III-V semiconductors such as InAs or InSb. The Majorana theory requires a clean semiconductor nanowire while the current experiments are disorder-limited. Recently, PbTe nanowires have been proposed to overcome the disorder issue owing to their large dielectric constant (~1350). Meanwhile, these nanowires were grown using selective area epitaxy and subjected to quantum transport characterizations on the field effect mobility, weak antilocalization, Aharonov-Bohm oscillations, and quantum dots. So far, the key question of whether superconducting proximity effect in PbTe nanowires exists is still pending. Here, we demonstrate the induced superconductivity in PbTe nanowires coupled to a superconductor Pb, whose gap is much larger than Al. Josephson junction devices based on this hybrid can reveal a gate-tunable supercurrent in the open regime and a hard-induced superconducting gap in the tunneling regime. We also have observed a hard superconducting gap with sharp coherence peaks in N(normal metal)-NW(nanowire)-S(superconductor) devices. The gap size is ∼ 1 meV. Our works show that the combination of PbTe and Pb could work as a new material platform for Majorana searches.