Seminar By Wei Pan, Sandia National Labs

Title: Josephson effects in Dirac semimetal Cd₃As₂

Series: Condensed Matter Sciences Seminar

Host: Kun Yang

Abstract: Josephson junctions (JJs) made of topological quantum materials have attracted a great deal of current interests due to their non-trivial band topology and the capability of realizing topological superconductivity. Here, I wish to report our recent observations of novel Josephson effects in topological JJs and superconducting quantum interference devices (SQUIDs) mediated by Cd₃As₂, a topological Dirac semimetal. First, in aluminum- Cd₃As₂-aluminum JJs, a π periodic supercurrents are observed. Our data analysis suggests that this π period could arise from interference between the induced bulk superconductivity and the induced Fermi-arc surface superconductivity. Moreover, we observe that in Cd₃As₂ SQUIDs this phase coupling between the surface-bulk superconducting channels is responsible for a surprising discovery of the Leggett modes, a collective quantum phenomenon predicted more than 50 years ago. Finally, we show that this phase coupling can further induce time-reversal symmetry breaking and, therefore, can give rise to a zero-field Josephson diode effect in asymmetric Cd₃As₂ SQUIDs.

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. This abstract describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. DOE or the United States Government.