Zero-Field Josephson Diode Effect in Dirac Semimetal-Based Asymmetric SQUIDs

Conventional diodes are characterized by their non-reciprocal charge transport and are ubiquitous in electronic devices. Within superconducting electronics, the superconducting diode effect (SDE) has attracted interest in recent years. Superconducting diodes are characterized by an asymmetry in positive and negative switching currents and could potentially find utility in a growing number of applications at cryogenic temperatures in the Quantum Information Sciences. Currently, many superconducting diodes require an external magnetic field or ferromagnetic layers to break time-reversal symmetry and induce the SDE. In this talk, we will discuss the <i>zero-field </i>SDE in asymmetric superconducting quantum interference devices (SQUID) based on Dirac semimetals. In this case, the Josephson effects in the SQUID arms dictate the non-reciprocity (Josephson diode effect) and we theoretically explore the role of surface and bulk states in Dirac semimetals. We will discuss how coupling of surface and bulk states can give rise to a diode effect in the <i>absence </i>of external magnetic fields or ferromagnetic layers. We will then present experimental results showing a zero-field SDE in asymmetric SQUIDs based on Dirac semimetal Cd₃As₂.<br/><br/>J.J.C, E.R., and W.P. acknowledge support from DOE, Grant No DE-SC0022245. The work at Sandia was also supported by LDRD projects. Device fabrication was performed at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of BES, user facility. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. DOE's National Nuclear Security Administration under contract DE-NA0003525.