Topological Superconductivity in a Phase-Controlled Josephson Junction

While signatures of Majorana bound states have been observed in one-dimensional systems, there is an ongoing effort to find alternative platforms that do not require fine-tuning and can be easily scalable. Using a Josephson junction made of HgTe quantum well coupled to thin-film aluminum, we can tune between a trivial and a topological superconducting state by controlling the phase difference φ and an applied in-plane magnetic field, as we measure the tunneling conductance at the edge of the junction. At low magnetic fields, we observe a minimum in the tunneling spectra near zero bias, consistent with a trivial superconductor. As the field increases, the tunneling conductance develops a zero-bias peak which persists over a range of φ that expands systematically with increasing magnetic fields. Consistent with theoretical predictions for this system, our observation establishes this system as a promising platform for realizing topological superconductivity and for creating and manipulating Majorana modes in two-dimensional systems.