Recently, Academician Dapeng Yu, Dean of the Shenzhen Institute of Quantum Science and Engineering (SIQSE) at Southern University of Science and Technology, and postdoctoral researcher Caizhen Li, cooperated with Professor Zhimin Liao from Peking University, Assistant Professor Chuan Li and Professor Alexander Brinkman from University of Twente, the Nertherlands, have made new progress on the quantum control of Dirac semimetal superconducting hetero-junctions. The relevant results was published in the journal Nature Communications under the title "Fermi-arc supercurrent oscillations in Dirac semimetal Josephson junctions".

  Dirac semimetal is a new topological material. The unique electronic band structure of this system makes it exhibit many novel properties, e.g., chiral anomaly and Fermi-arc surface states. Theoretical predictions show that combining the topological surface states with superconducting is expected to realize the Majorana bound states, the brick-stone for topological quantum computing, which has attracted great attention in condensed matter physics.  

  In this work, Caizhen Li and coauthors synthesized high quality Cd3As2 nanoplates, the property of low carrier density makes it able to tune the chemical potential using a back gate voltage to study the Fermi-arc surface states near the Dirac point. The researchers fabricated Nb-Cd3As2-Nb Josephson junctions and gate-tunable supercurrent are observed. Without magnetic field, the supercurrent is carried by both bulk and surface states. With increasing an in-plane magnetic field, the bulk-carried supercurrent is strongly suppressed and the Fermi-arc surface states become manifest. In the surface state dominant regime, the critical supercurrent shows a maximum value near the Dirac point, consistent with the fact that the Fermi arcs have the maximum density of states at the Dirac point. The maximum critical supercurrent at Dirac point in 3D Dirac semimetal is different from the case of 2D Dirac states in topological insulators and graphene. Furthermore, the Fermi-arc supercurrent shows periodic oscillations with in-plane parallel magnetic field, which is attributed to the in-plane field orbital interference of the surface Fermi arcs. Such magnetic field and gate modulation of superconducting Fermi arcs opens up a new avenue for the manipulation of Majorana bound states, which might be significant to the topological quantum computation.

Figure: (a) The difference resistance dV/dI as a function of magnetic field B and Idc; (b) The enlarged dV/dI map of the grey dotted box in a; (c) The critical current as a function of back gate voltage at different magnetic fields; (d) The Fermi arcs for the Fermi level close to (top) and away from Dirac point (below).

  Caizhen Li and Anqi Wang (a postgraduate from Peking University) are co-first authors of the paper. Professor Zhimin Liao and Assistant Professor Chuan Li are corresponding authors. This work was supported by National Key Research and Development Program of China and NSFC.