nanowires

Three-dimensional (3D) Dirac semimetals have attracted considerable attention owing to their exotic properties, both predicted in theory and recently demonstrated experimentally. Here, we demonstrate single quantum dots confined with two p-n junctions in 3D Dirac semimetal Cd₃As₂ nanowires under high magnetic fields. The device can be operated in two different regimes: (i) an n-type channel between n*-type leads underneath the source-drain contacts, creating an open regime (n*-n-n* configuration); (ii) a p-type channel in the middle of the nanowire, forming a p-type quantum dot (QD) (n*-p-n* configuration). At zero magnetic field, the quantum confinement effect vanishes in the n*-p-n* QD because the Dirac fermions penetrate p-n junctions with high transmission probability (Klein tunneling). However, the high magnetic fields bend the Dirac fermion trajectories at the p-n junction due to cyclotron motion, preventing the Klein tunneling. This results in a strong confinement at p-n junctions of Dirac materials. In this regime, the device shows clean Coulomb diamonds, indicating that a single QD is formed in a Dirac semimetal nanowire.