Unconventional Superconductivity at Mesoscopic Point-contacts on the 3-Dimensional Dirac Semi-metal Cd$_3$As$_2$

TL;DR

This study reports the discovery of unconventional superconductivity at mesoscopic point-contacts between silver and the Dirac semi-metal Cd$_3$As$_2$, revealing a new phase with potential topological properties and high-temperature pseudogap features.

Contribution

It demonstrates that mesoscopic point-contacts induce superconductivity in Cd$_3$As$_2$, a non-superconducting Dirac semi-metal, revealing a novel confined superconducting phase.

Findings

Superconductivity observed up to 6 K at Ag/Cd$_3$As$_2$ contacts.

Spectroscopic gap of 6.5 meV persists up to 13 K.

Emergence of a robust pseudogap in the normal state.

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.