The combination of superconductivity and surface states in Dirac semimetal can produce a $4\pi$-periodic supercurrent in a Josephson junction configuration, which can be revealed by the missing of odd Shapiro steps (especially the $n=1$ step). However, the suppression of the $n=1$ step is also anticipated in the high-power oscillatory regime of the ordinary $2\pi$-periodic Josephson effect, which is irrelevant to the $4\pi$-periodic supercurrent. Here, in order to identify the origin of the suppressed $n=1$ step, we perform the measurements of radio frequency irradiation on Nb–Dirac semimetal ${\mathrm{Cd}}_3{\mathrm{As}}_2$ nanowire–Nb junctions with continuous power dependence at various frequencies. Besides the $n=1$ step suppression, we uncover a residual supercurrent of first node at the $n=0$ step, which provides a direct and predominant signature of the $4\pi$-periodic supercurrent. Furthermore, by tuning the gate voltage, we can modulate the surface and bulk state contribution and the visibility of the $n=1$ step. Our results provide deep insights to explore the topological superconductivity in Dirac semimetals.

This article describes a Delphi study aiming to investigate which quantum mechanics topics experts consider to be important to teach at the secondary level, and what arguments these experts give. A series of three questionnaires was administered to experts in the fields of quantum physics, mathematics, chemistry and biophysics (n = 17, 12, 11 for the first, second, and third questionnaires, respectively; the number of participants changed due to attrition). Several experts from this group (n = 9) were also interviewed. Results show that there is consensus on the topics considered to be important, i.e. duality, wave functions and atoms. Experts mainly based their topic ranking on relations between concepts, and on what quantum mechanics topics they consider to be fundamental. The topics that were considered less important were often described as too difficult or too complex.

A three-dimensional Dirac semimetal has bulk Dirac cones in all three momentum directions and Fermi arc like surface states, and can be converted into a Weyl semimetal by breaking time-reversal symmetry. However, the highly conductive bulk state usually hides the electronic transport from the surface state in Dirac semimetal. Here, we demonstrate the supercurrent carried by bulk and surface states in $\mathrm{Nb}-{\mathrm{Cd}}_3{\mathrm{As}}_2$ nanowire-Nb short and long junctions, respectively. For the $\sim 1-\mu \mathrm{m}$-long junction, the Fabry-Pérot interferences-induced oscillations of the critical supercurrent are observed, suggesting the ballistic transport of the surface states carried supercurrent, where the bulk states are decoherent and the topologically protected surface states still stay coherent. Moreover, a superconducting dome is observed in the long junction, which is attributed to the enhanced dephasing from the interaction between surface and bulk states as tuning gate voltage to increase the carrier density. The superconductivity of topological semimetal nanowire is promising for braiding of Majorana fermions toward topological quantum computing.