Microwave Driven Epitaxial Josephson Junctions with an In-plane Magnetic Field

The hunt for topological superconductivity has accelerated in recent years as it provides a suitable platform for fault-tolerant quantum computing. Planar epitaxial Al-InAs Josephson junctions (JJs) are a promising candidate to realize topological superconducting states due to their high transparency, strong spin-orbit coupling, and large g-factor. When a microwave drive is applied to a JJ, quantizied integer and possibly fractional constant voltage steps, Shapiro steps, appear in the Voltage-Current characteristic due to phase locking. The presence of the 4π-periodic Josephson effect, one of the signatures of topological superconductivity, results in missing odd Shapiro steps. However, highly transparent JJs in the topologically trivial regime, without a magnetic field, have also been shown to exhibit missing odd Shapiro. Theory predicts these JJs can be driven into a topological superconducting phase by applying an in-plane magnetic field. We study the effect of the Zeeman field on trivial and non-trivial signatures with and without microwave drive. We further consider the field angle and junction geometry on the observed signatures.