Enhancing topological superconductivity in phase-biased Josephson junctions*

The manifestation of spin-orbit coupling in proximitized superconductivity is central to the formation of topological superconducting phases.  The most exciting property of topological superconductivity is its capacity to harbor non-Abelian excitations that could be the key to developing fault-tolerant quantum computers. Here we study planar Josephson junctions of highly transparent, epitaxial Al contacts on a near-surface InGaAs-InAs-InGaAs quantum well confinining a 2DEG with strong spin-orbit coupling and large g-factor.  This system has been predicted to support topological superconductivity and previous experimental work has yielded promising results consistent with theoretically derived signatures of nontrivial topology.  Our junction is embedded in a SQUID geometry with an integrated remote flux line, enabling phase-sensitive measurements and phase-control via magnetic flux applied far from the junction so as to preserve the superconducting gap.  We study the current-phase relation of the junction as a function of in-plane Zeeman field and gate voltage.  We further study the local density of states near the edge of the junction via tunneling spectroscopy with a quantum point contact while the junction is π-phase-biased, where the Zeeman condition for topology is relaxed.