Epitaxial Al/InAs Josephson Junction Arrays With and Without Mirror Symmetries

Voltage-tunable Josephson junction arrays based on superconductor-semiconductor materials provide a playground for artificial lattices as new quantum simulators. Through tuning the coupling between superconducting islands, the symmetry of 2D lattice as well as the Josephson and charging energies can be modulated. We fabricate Al/InAs Josephson junction arrays in square and hexagonal lattices, and compare their electronic response in various in-plane and out-of-plane magnetic fields. We study their dependence on the coupling between islands, the array structure, and the size of the unit cell. We engineer array structures such that mirror symmetries are broken, and apply magnetic fields to break time-reversal-symmetry. By analyzing transport measurements as a function of in-plane magnetic field angle we can identify the impact of spin-orbit coupling on the system. We also discuss how gate-tuning the Josephson coupling in the arrays can be used to further explore signatures of phase transitions.