Observation of surface superconductivity in a three-dimensional Dirac material

TL;DR

This study reports the coexistence of surface superconductivity and a three-dimensional topological Dirac state in BaMg₂Bi₂, revealing surface superconductivity at 4.77 K and highlighting its potential for exploring topological superconductivity.

Contribution

It demonstrates the presence of surface superconductivity in a topological Dirac material, providing a new platform for studying the interplay between superconductivity and topological states.

Findings

Superconductivity observed up to 4.77 K at ambient pressure.

Surface superconductivity characterized as two-dimensional.

BaMg₂Bi₂ identified as an ideal Dirac material with the Dirac point near the Fermi level.

Abstract

Superconductivity becomes more interesting when it encounters dimensional constraint or topology, because it is of importance for exploring exotic quantum phenomena or developing superconducting electronics. Here we report the coexistence of naturally formed surface superconducting state and three-dimensional topological Dirac state in single crystals of BaMg$_2$Bi$_2$. The electronic structure obtained from the first-principles calculations demonstrates that BaMg$_2$Bi$_2$ is an ideal Dirac material, in which the Dirac point is very close to the Fermi level and no other energy band crosses the Fermi level. Superconductivity up to 4.77 K can be observed under ambient pressure in the measurements of resistivity. The angle dependent magnetoresistance reveals the two-dimensional characteristic of superconductivity, indicating that superconductivity occurs on the surface of the sample and is absent in the bulk state. Our study not only provides BaMg$_2$Bi$_2$ as a suitable platform to study the interplay between superconductivity and topological Dirac state, but also indicates that MgBi-based materials may be a promising system for exploring new superconductors.