Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

Abstract

Since the three dimensional (3D) Dirac semi-metal Cd 3 As 2 exists close to topological phase boundaries, in principle it should be possible to drive it into exotic new phases, like topological superconductors, by breaking certain symmetries. Here we show that the mesoscopic point-contacts between silver (Ag) and Cd 3 As 2 exhibit superconductivity up to a critical temperature (onset) of 6 K while neither Cd 3 As 2 nor Ag are superconductors. A gap amplitude of 6.5 meV is measured spectroscopically in this phase that varies weakly with temperature and survives up to a remarkably high temperature of 13 K indicating the presence of a robust normal-state pseudogap. The observations indicate the emergence of a new unconventional superconducting phase that exists only in a quantum mechanically confined region under a point-contact between a Dirac semi-metal and a normal metal. * These authors contributed equally to the work † ashok@chemistry.iitd.ac.in ‡ goutam@iisermohali.ac.in 1 arXiv:1410.2072v1 [cond-mat.supr-con]

Pressure-induced superconductivity in the three-dimensional topological Dirac semimetal Cd3As2

“…Interestingly, we also notice two recent point contact studies on Cd 3 As 2 polycrystal and single crystal, respectively. 43,44 In both studies, indication of superconductivity was found around the point contact region on the surface, with T c comparable to ours. In particular, no superconductivity is observed by the 'soft' point contact technique, therefore it was suggested that the superconductivity observed around the point contact region under the 'hard' tip might be induced by the local pressure.…”

Bulk and surface states carried supercurrent in ballistic Nb-Dirac semimetal Cd3As2 nanowire-Nb junctions

“…Recently, theoretical investigations have proposed that the Dirac semimetal Cd 3 As 2 is promising for topological superconductivity [17,18]. In addition, the signatures of unconventional superconductivity in Cd 3 As 2 have been reported through pressure-loaded [19] and point-contacted [20,21] experiments. However, the proximity effect-induced superconductivity in Cd 3 As 2 has still not yet been achieved, which is more important for practical devices without complicated pressure loading.…”

Higgs amplitude mode in massless Dirac fermion systems

“…On the experimental side, the availability of the honeycomb optical lattice 18 and the tunable attractive interaction by Feshbash resonance 19 give a possible test ground for this study. Besides, the expected unique feature of the Higgs mode in superconducting Dirac semimetal can be used as an important experimental characterization to distinguish it from the normal superconductors 21,22 . In this paper we study the quenched dynamics in the weak coupling limit by using the Anderson pseudo-spin formalism 23 .…”