Ballistic PbTe Nanowire Devices

Abstract

Disorder is the primary obstacle in the current Majorana nanowire experiments. Reducing disorder or achieving ballistic transport is thus of paramount importance. In clean and ballistic nanowire devices, quantized conductance is expected, with plateau quality serving as a benchmark for disorder assessment. Here, we introduce ballistic PbTe nanowire devices grown by using the selective-area-growth (SAG) technique. Quantized conductance plateaus in units of 2e 2/h are observed at zero magnetic field. This observation represents an advancement in diminishing disorder within SAG nanowires as most of the previously studied SAG nanowires (InSb or InAs) have not exhibited zero-field ballistic transport. Notably, the plateau values indicate that the ubiquitous valley degeneracy in PbTe is lifted in nanowire devices. This degeneracy lifting addresses an additional concern in the pursuit of Majorana realization. Moreover, these ballistic PbTe nanowires may enable the search for clean signatures of the spin–orbit helical gap in future devices.

Hard Superconducting Gap in PbTe Nanowires

“…Similar trend has also been observed before in our PbTe nanowire devices. [37,53] The outside-gap conductance exhibits Fabry-Pérotlike oscillations over 𝑉G, possibly caused by the scattering between the barrier region and the drain contact. These oscillations can also affect the estimation of the normal state conductance (𝐺N).…”

Selective-Area-Grown PbTe-Pb Planar Josephson Junctions for Quantum Devices

“…Here, we present the PbTe-Pb hybrid as a new planar JJ material platform for exploring topological superconductivity and other potential applications, such as gate tunable qubits. − While the PbTe-Pb hybrid has recently been proposed in its nanowire form as a Majorana candidate with promising experimental progress, − in this paper, we realize its 2DEG version, motivated by the Majorana proposals for topological planar JJs. , Selective area growth (SAG) of PbTe film has been previously achieved on InP, a substrate that is lattice-mismatched with PbTe . In this work, the SAG PbTe film is grown on a lattice-matched substrate to minimize the disorder.…”

“…Figure briefly illustrates the device design, growth procedure, and material analysis. We started with a CdTe/Pb 0.92 Eu 0.08 Te substrate − and covered it with a thin SiN dielectric layer. A Hydrogen SilsesQuioxane (HSQ) shadow wall was fabricated prior to the Pb 0.92 Eu 0.08 Te growth .…”